Occupational stress

From Wikipedia, the free encyclopedia

Occupational stress is stress related to one's job. Occupational stress often stems from unexpected responsibilities and pressures that do not align with a person's knowledge, skills, or expectations, inhibiting one's ability to cope. Occupational stress can increase when workers do not feel supported by supervisors or colleagues, or feel as if they have little control over work processes.

Models

Because stress results from the complex interactions between a large system of interrelated variables, there are several psychological theories and models that address occupational stress.

Person-environment fit model: This model "suggests that the match between a person and their work environment is key in influencing their health. For healthy conditions, it is necessary that employees’ attitudes, skills, abilities and resources match the demands of their job, and that work environments should meet workers’ needs, knowledge, and skills potential. Lack of fit in either of these domains can cause problems, and the greater the gap or misfit (either subjective or objective) between the person and their environment, the greater the strain as demands exceed abilities, and need exceeds supply. These strains can relate to health related issues, lower productivity, and other work problems. Defense mechanisms, such as denial, reappraisal of needs, and coping, also operate in the model, to try and reduce subjective misfit".

Job characteristics model: This model "focuses on important aspects of job characteristics, such as skill variety, task identity, task significance, autonomy, and feedback. These characteristics are proposed to lead to ‘critical psychological states’ of experienced meaningfulness, and experienced responsibility and knowledge of outcomes. It is proposed that positive or negative work characteristics give rise to mental states which lead to corresponding cognitive and behavioral outcomes, e.g. motivation, satisfaction, absenteeism, etc. In conjunction with the model, Hackman and Oldham (1980) developed the Job Diagnostic Survey, a questionnaire for job analysis, which implies key types of job-redesign including combining tasks, creating feedback methods, job enrichment, etc."

Diathesis–stress model: This model looks at behaviors as a susceptibility burden together with stress from life experiences. It is useful to distinguish stressful job conditions or stressors from an individual's reactions or strains. Strains can be mental, physical or emotional. Occupational stress can occur when there is a discrepancy between the demands of the environment/workplace and an individual’s ability to carry out and complete these demands. Often a stressor can lead the body to have a physiological reaction that can strain a person physically as well as mentally. A variety of factors contribute to workplace stress such as excessive workload, isolation, extensive hours worked, toxic work environments, lack of autonomy, difficult relationships among coworkers and management, management bullying, harassment and lack of opportunities or motivation to advancement in one’s skill level.

Job demands-resources model: This model posits that strain are a response to imbalance between demands of one's job and the resources he or she has to deal with those demands.

• Job demands: the physical, psychological, social, or organizational aspects of a job that require sustained physical and/or psychological effort or skills. Therefore, they are associated with expenditure of time and energy.
• Job resources: the physical, psychological, social, or organizational aspects of the job that aid in achieving work goals; reduce job demands and the associated physiological and psychological cost; stimulate personal growth, learning, and development.

Effort-reward imbalance model: This model focuses on the reciprocal relationship between efforts and rewards at work. "More specifically, the ERI Model claims that work characterized by both high efforts and low rewards represents a reciprocity deficit between high ‘costs’ and low ‘gains’, which could elicit negative emotions in exposed employees. The accompanying feelings may cause sustained strain reactions. So, working hard without receiving adequate appreciation or being treated fairly are examples of a stressful imbalance. Another assumption of the ERI Model concerns individual differences in the experience of effort-reward imbalance. It is assumed that employees characterized by a motivational pattern of excessive job-related commitment and a high need for approval (i.e., overcommitment) will respond with more strain reactions to an effort-reward imbalance, in comparison with less overcommitted people."

Origins

Sources of occupational stress come from:

• a toxic work environment
• negative workload
• isolation
• financial pressures
• types of hours worked
• role conflict & role ambiguity
• lack of autonomy, career development barriers
• difficult relationships with administrators and/or coworkers
• managerial bullying
• harassment
• organizational climate

These individual sources demonstrate that stress can occur specifically when a conflict arises from the job demands of the employee and the employee itself. If not handled properly, the stress can become distress.

• Coping: the ability of the employee coping with the specific hours worked, the level of productive rate expected, the physical environment, as well as the expectancy of the work desired by management. For instance, research shows that night shifts in particular has a high possibility of negative impact towards the health of the employee. In relation to this, approximately 20 percent of night shift workers have experienced psycho-physiological dysfunctions, including heart diseases. Extreme factors can affect the competence levels of employees.
• Role in the organization: associated with the hierarchical ranking of that particular employee within the organization. Upper management is entitled to oversee the overall functioning of the organization. This causes potential distress as the employee must be able to perform simultaneous tasks.
• Career development: Security of their occupation, promotion levels, etc. are all sources of stress, as this business market in terms of technology of economic dominance is ever-changing.
• Interpersonal relationships within the workplace: The workplace is a communication and interaction-based industry. These relationships (either developed or developing) can be problematic or positive. Common stressors include harassment, discrimination, biased opinions, hearsay, and other derogatory remarks.
• Organizational climate or structure: The overall communication, management style, and participation among groups of employees are variables to be considered. In essence, the resultant influence of the high participation rate, collaborative planning, and equally dispersed responsibilities provides a positive effect on stress reduction, improved work performance, job satisfaction, and decreased psychosomatic disorders.

Prevalence

Distress is a prevalent and costly problem in today's workplace. About one-third of workers report high levels of stress. 20–30% of workers in different sectors of the European Union reported in 2007 that they believed work-related stress was potentially affecting their health. Three-quarters of employees believe the worker has more on-the-job stress than a generation ago. In Great Britain, a sixth of the workforce experiences occupational stress every year. Evidence also suggests that distress is the major cause of turnover in organizations. With continued distress at the workplace, workers will develop psychological and physiological dysfunctions and decreased motivation in excelling in their position. Increased levels of job stress are determined by the awareness of having little control but lots of demands in the work area. Occupational stress and its sequelae represent the majority of work-related illnesses causing missed work days. Those in the protective services, transportation and materials moving, building grounds cleaning and maintenance, and healthcare are more susceptible to both work injuries and illnesses, as well as work-related stress.

Negative health effects

Stress-related disorders encompass a broad array of conditions, including psychological disorders (e.g., depression, anxiety, post-traumatic stress disorder) and other types of emotional strain (e.g., dissatisfaction, fatigue, tension, etc.), maladaptive behaviors (e.g., aggression, substance abuse), and cognitive impairment (e.g., concentration and memory problems). In turn, these conditions may lead to poor work performance, higher absenteeism, less work productivity or even injury. "If untreated, consistently high stress can become a chronic condition, which can exacerbate existing mental health conditions and chronic physical conditions (diabetes, hypertension, weak immune system). These conditions not only diminish the well-being of workers and increase the employer's health benefits expenses, they contribute to increased injury incidence. Consistently high levels of stress increase the risk of occupational injury. A study of light/short haul truckers, a group that experiences high rates of injury and mental health issues, found that frequent stress increased the odds of occupational injury by 350%."

Job stress is also associated with various biological reactions that may lead ultimately to compromised health, such as cardiovascular disease, or in extreme cases death. Due to the high pressure and demands in the work place the demands have been shown to be correlated with increased rates of heart attack, hypertension and other disorders. In New York, Los Angeles, and London, among other municipalities, the relationship between job stress and heart attacks is acknowledged.

Problems at work are more strongly associated with health complaints than are any other life stressor-more so than even financial problems or family problems. Occupational stress accounts for more than 10% of work-related health claims. Many studies suggest that psychologically demanding jobs that allow employees little control over the work process increase the risk of cardiovascular disease. Research indicates that job stress increases the risk for development of back and upper-extremity musculoskeletal disorders. Other disorders that can be caused or exacerbated by occupational stress include sleep disorders, headache, mood disorders, upset stomach, hypertension, high cholesterol, autoimmune disease, cardiovascular disease, depression, and anxiety. Stress at work can also increase the risk of acquiring an infection and the risk of accidents at work.

High levels of stress are associated with substantial increases in health service utilization. Workers who report experiencing stress at work also show excessive health care utilization. In a 1998 study of 46,000 workers, health care costs were nearly 50% greater for workers reporting high levels of stress in comparison to “low risk” workers. The increment rose to nearly 150%, an increase of more than $1,700 per person annually, for workers reporting high levels of both stress and depression. Health care costs increase by 200% in those with depression and high occupational stress. Additionally, periods of disability due to job stress tend to be much longer than disability periods for other occupational injuries and illnesses.

Physiological reactions to stress can have consequences for health over time. Researchers have been studying how stress affects the cardiovascular system, as well as how work stress can lead to hypertension and coronary artery disease. These diseases, along with other stress-induced illnesses tend to be quite common in American work-places. There are four main physiological reactions to stress:

• Blood is shunted to the brain and large muscle groups, and away from extremities, skin, and organs that are not currently serving the body.
• An area near the brain stem, known as the reticular activating system, goes to work, causing a state of keen alertness as well as sharpening of hearing and vision.
• Energy-providing compounds of glucose and fatty acids are released into the bloodstream.
• The immune and digestive systems are temporarily shut down.

Gender

Frustrated man at a desk

 

Men and women are exposed to many of the same stressors. Although men and women might not differ in overall strains, women are more likely to experience psychological distress, whereas men experience more physical strain. Desmarais and Alksnis suggest two explanations for the greater psychological distress of women. First, the genders may differ in their awareness of negative feelings, leading women to express and report strains, whereas men deny and inhibit such feelings. Second, the demands to balance work and family result in more overall stressors for women that leads to increased strain.

The Kenexa Research Institute released a global survey of almost 30,000 workers which showed that females suffered more workplace distress than their male counterparts. According to the survey, women's stress level were 10% higher for those in supervisory positions, 8% higher stress in service and production jobs than men, and 6% higher in middle and upper management than men in the same position.

Causes

Job stress results from various interactions of the worker and the environment of the work they perform their duties. Location, gender, environment, and many other factors contribute to the buildup of stress. Job stress results from the interaction of the worker and the conditions of work. Views differ on the importance of worker characteristics versus working conditions as the primary cause of job stress. The differing viewpoints suggest different ways to prevent stress at work. Differences in individual characteristics such as personality and coping skills can be very important in predicting whether certain job conditions will result in stress. In other words, what is stressful for one person may not be a problem for someone else. This viewpoint underlies prevention strategies that focus on workers and ways to help them cope with demanding job conditions. In general, occupational stress is caused by a mismatch between perceived effort and perceived reward, and/or a sense of low control in a job with high demands. Low social support at work and job insecurity can also increase occupational stress. Psychosocial stressors are a major cause of occupational stress.

Working conditions

Although the importance of individual differences cannot be ignored, scientific evidence suggests that certain working conditions are stressful to most people. Such evidence argues for a greater emphasis on working conditions as the key source of job stress, and for job redesign as a primary prevention strategy. Large surveys of working conditions, including conditions recognized as risk factors for job stress, were conducted in member states of the European Union in 1990, 1995, and 2000. Results showed a time trend suggesting an increase in work intensity. In 1990, the percentage of workers reporting that they worked at high speeds at least one-quarter of their working time was 48%, increasing to 54% in 1995 and to 56% in 2000. Similarly, 50% of workers reported they work against tight deadlines at least one-fourth of their working time in 1990, increasing to 56% in 1995 and 60% in 2000. However, no change was noted in the period 1995–2000 (data not collected in 1990) in the percentage of workers reporting sufficient time to complete tasks.

Workload

In an occupational setting, dealing with workload can be stressful and serve as a stressor for employees. There are three aspects of workload that can be stressful.

Quantitative workload or overload: Having more work to do than can be accomplished comfortably.

Qualitative workload: Having work that is too difficult.

Underload: Having work that fails to use a worker's skills and abilities.

Workload as a work demand is a major component of the demand-control model of stress. This model suggests that jobs with high demands can be stressful, especially when the individual has low control over the job. In other words, control serves as a buffer or protective factor when demands or workload is high. This model was expanded into the demand-control-support model that suggests that the combination of high control and high social support at work buffers the effects of high demands.

As a work demand, workload is also relevant to the job demands-resources model of stress that suggests that jobs are stressful when demands (e.g., workload) exceed the individual's resources to deal with them.

Long hours

A substantial percentage of Americans work very long hours. By one estimate, more than 26% of men and more than 11% of women worked 50 hours per week or more in 2000. These figures represent a considerable increase over the previous three decades, especially for women. According to the Department of Labor, there has been a rise in the number of hours in the work place by employed women, an increase in extended work weeks (>40 hours) by men, and a considerable increase in combined working hours among working couples, particularly couples with young children.

Evidence of occupational stress due to an individual's status in the workplace

Status

A person's status in the workplace can also affect levels of stress. While workplace stress has the potential to affect employees of all categories; those who have very little influence to those who make major decisions for the company. However, employees who have less control over their jobs) are more likely to report psychological symptoms than workers who have more control over their work. Managers as well as other kinds of workers are vulnerable to work overload.

Economic factors

Economic factors that employees face in the 21st century have been linked to increased stress levels. Researchers and social commentators have pointed out that the computer and communications revolutions have made companies more efficient and productive than ever before. This increase in productivity, however, has caused higher expectations and greater competition, putting more stress on the employee.

The following economic factors may lead to workplace stress:

• Pressure from investors, who can quickly withdraw their money from company stocks.
• The lack of trade and professional unions in the workplace
• Inter-company rivalries caused by the efforts of companies to compete globally
• The willingness of companies to swiftly lay off workers to cope with changing business environments

Bullying

Bullying in the workplace can also contribute to stress. This can be broken down into five categories:

• Threat to profession status
• Threat to personal status
• Isolation
• Excess work
• Destabilization, i.e. lack of credit for work, meaningless tasks, etc.

This can create a hostile work environment for employees, which in turn can affect their work ethic and contribution to the organization.

Narcissism and psychopathy

Thomas suggests that there tends to be a higher level of stress with people who work or interact with a narcissist, which in turn increases absenteeism and staff turnover. Boddy finds the same dynamic where there is a corporate psychopath in the organisation.

Workplace conflict

Interpersonal conflict among people at work has been shown to be one of the most frequently noted stressors for employees. Conflict has been noted to be an indicator of the broader concept of workplace harassment. It relates to other stressors that might co-occur, such as role conflict, role ambiguity, and workload. It also relates to strains such as anxiety, depression, physical symptoms, and low levels of job satisfaction.

Sexual harassment

Women are more likely than men to experience sexual harassment, especially for those working in traditionally masculine occupations. In addition, a study indicated that sexual harassment negatively affects workers' psychological well-being. Another study found that level of harassment at workplaces lead to differences in performance of work related tasks. High levels of harassment were related to the worst outcomes, and no harassment was related to least negative outcomes. In other words, women who had experienced a higher level of harassment were more likely to perform poorly at workplaces.

Occupational group

Lower occupational groups are at higher risk of work-related ill health than higher occupational groups. This is in part due to adverse work and employment conditions. Furthermore, such conditions have greater effects on ill-health to those in lower socio-economic positions.

Effects

Stressful working conditions can lead to three types of strains: Behavioral (e.g., absenteeism or poor performance), physical (e.g., headaches or coronary heart disease), and psychological (e.g., anxiety or depressed mood). Physical symptoms that may occur because of occupational stress include fatigue, headache, upset stomach, muscular aches and pains, weight gain or loss, chronic mild illness, and sleep disturbances. Psychological and behavioral problems that may develop include anxiety, irritability, alcohol and drug use, feeling powerless and low morale. The spectrum of effects caused by occupational stress includes absenteeism, poor decision making, lack of creativity, accidents, organizational breakdown or even sabotage. If exposure to stressors in the workplace is prolonged, then chronic health problems can occur including stroke. An examination was of physical and psychological effects of workplace stress was conducted with a sample of 552 female blue collar employees of a microelectronics facility. It was found that job-related conflicts were associated with depressive symptoms, severe headaches, fatigue, rashes, and other multiple symptoms. Studies among the Japanese population specifically showed a more than 2-fold increase in the risk of total stroke among men with job strain (combination of high job demand and low job control). Those in blue-collar or manual labor jobs are more likely to develop heart disease compared to those in white-collar jobs. Along with the risk of stroke, stress can raise the risk of high blood pressure, immune system dysfunction, coronary artery disease. Prolonged occupational stress can lead to occupational burnout. Occupational stress can also disrupt relationships.

The effects of job stress on chronic diseases are more difficult to ascertain because chronic diseases develop over relatively long periods of time and are influenced by many factors other than stress. Nonetheless, there is some evidence that stress plays a role in the development of several types of chronic health problems—including cardiovascular disease, musculoskeletal disorders, and psychological disorders. Job stress and strain has been associated with poor mental health and wellbeing over a 12-year period.

Occupational stress has negative effects for organizations and employers. Occupational stress is the cause of approximately 40% of turnover and 50% of workplace absences. The annual cost of occupational stress and its effects in the US is estimated to be over $60 billion to employers and $250–300 billion to the economy.

Prevention

A combination of organizational change and stress management is often the most useful approach for preventing stress at work. Both organizations and employees can employ strategies at organizational and individual levels. Generally, organizational level strategies include job procedure modification and employee assistance programs (EAP). Individual level strategies include taking vacation. Getting a realistic job preview to understand the normal workload and schedules of the job will also help people to identify whether or not the job fit them. 

How an Organization Can Prevent Job Stress

• Ensure that the workload is in line with workers' capabilities and resources.
• Design jobs to provide meaning, stimulation, and opportunities for workers to use their skills.
• Clearly define workers' roles and responsibilities.
• To reduce workplace stress, managers may monitor the workload given out to the employees. Also while they are being trained they should let employees understand and be notified of stress awareness.
• Give workers opportunities to participate in decisions and actions affecting their jobs.
• Improve communications-reduce uncertainty about career development and future employment prospects.
• Provide opportunities for social interaction among workers.
• Establish work schedules that are compatible with demands and responsibilities outside the job.
• Combat workplace discrimination (based on race, gender, national origin, religion or language).
• Bringing in an objective outsider such as a consultant to suggest a fresh approach to persistent problems.
• Introducing a participative leadership style to involve as many subordinates as possible to resolve stress-producing problems.
• Encourage work-life balance through family-friendly benefits and policies

An insurance company conducted several studies on the effects of stress prevention programs in hospital settings. Program activities included (1) employee and management education on job stress, (2) changes in hospital policies and procedures to reduce organizational sources of stress, and (3) the establishment of employee assistance programs. In one study, the frequency of medication errors declined by 50% after prevention activities were implemented in a 700-bed hospital. In a second study, there was a 70% reduction in malpractice claims in 22 hospitals that implemented stress prevention activities. In contrast, there was no reduction in claims in a matched group of 22 hospitals that did not implement stress prevention activities.

Telecommuting is another way organizations can help reduce stress for their workers. Employees defined telecommuting as "an alternative work arrangement in which employees perform tasks elsewhere that are normally done in a primary or central workplace, for at least some portion of their work schedule, using electronic media to interact with others inside and outside the organization." One reason that telecommuting gets such high marks is that it allows employees more control over how they do their work. Telecommuters reported more job satisfaction and less desire to find a new job. Employees that worked from home also had less stress, improved work/life balance and higher performance rating by their managers.

A systematic review of stress-reduction techniques among healthcare workers found that cognitive behavioral training lowered emotional exhaustion and feelings of lack of personal accomplishment.

Signs and symptoms of excessive job and workplace stress

Signs and symptoms of excessive job and workplace stress include:

• Feeling anxious, irritable, or depressed
• Apathy, loss of interest in work
• Problems sleeping
• Fatigue
• Trouble concentrating

• Muscle tension or headaches
• Stomach problems
• Social withdrawal
• Loss of sex drive
• Using alcohol or drugs to cope

Both yoga and mindful-based stress reduction have been shown to reduce work-related stress. Nurses who participated in cognitive behavioral interventions had less perceived stress, a greater sense of coherence, and increased mood. 

Expanding research on stress: Contemporary opinions hold that jobs designed to support skill variety, task identity, significance, autonomy, and feedback, while providing for existence and growth needs, will sustain a healthier, greater satisfied workforce.

For team-oriented work environments, Patrick Lencioni's The Five Dysfunctions of a Team profiles the behavior of cohesive teams:

• They trust one another.
• They engage in unfiltered conflict around ideas.
• They commit to decisions and plans of action.
• They hold one another accountable for delivering against those plans.
• They focus on the achievement of collective results.

For immediate individual stress management, rudimentary mental coping strategies may be adopted in the work environment.

Cognitive epidemiology

From Wikipedia, the free encyclopedia

Cognitive epidemiology is a field of research that examines the associations between intelligence test scores (IQ scores or extracted g-factors) and health, more specifically morbidity (mental and physical) and mortality. Typically, test scores are obtained at an early age, and compared to later morbidity and mortality. In addition to exploring and establishing these associations, cognitive epidemiology seeks to understand causal relationships between intelligence and health outcomes. Researchers in the field argue that intelligence measured at an early age is an important predictor of later health and mortality differences.

Overall mortality and morbidity

A strong inverse correlation between early life intelligence and mortality has been shown across different populations, in different countries, and in different epochs."

A study of one million Swedish men found showed "a strong link between cognitive ability and the risk of death."

A similar study of 4,289 former US soldiers showed a similar relationship between IQ and mortality.

The strong correlation between intelligence and mortality has raised questions as to how better public education could delay mortality.

There is a known inverse correlation between socioeconomic position and health. A 2006 study found that controlling for IQ caused a marked reduction in this association.

Research in Scotland has shown that a 15-point lower IQ meant people had a fifth less chance of seeing their 76th birthday, while those with a 30-point disadvantage were 37% less likely than those with a higher IQ to live that long.

Another Scottish study found that once individuals had reached old age (79 in this study), it was no longer childhood intelligence or current intelligence scores that best predicted mortality but the relative decline in cognitive abilities from age 11 to age 79. They also found that fluid abilities were better predictors of survival in old age than crystallized abilities.

The relationship between childhood intelligence and mortality has even been found to hold for gifted children, those with an intelligence over 135. A 15-point increase in intelligence was associated with a decreased risk of mortality of 32%. This relationship was present until an intelligence score of 163 at which point there was no further advantage of a higher intelligence on mortality risk.

A meta-analysis of the relationship between intelligence and mortality found that there was a 24% increase in mortality for a 1SD (15 point) drop in IQ score. This meta-analysis also concluded that the association between intelligence and mortality was similar for men and women despite sex differences in disease prevalence and life expectancies.

A whole population follow-up over 68 years showed that the association with overall mortality was also present for most major causes of death. The exceptions were cancers unrelated to smoking and suicide.

There is also a strong inverse correlation between intelligence and adult morbidity. Long term sick leave in adulthood has been shown to be related to lower cognitive abilities, as has likelihood of receiving a disability pension.

Physical illness

Coronary heart disease

Among the findings of cognitive epidemiology is that men with a higher IQ have less risk of dying from coronary heart disease. The association is attenuated, but not removed, when controlling for socio-economic variables, such as educational attainment or income. This suggests that IQ may be an independent risk factor for mortality. One study found that low verbal, visuospatial and arithmetic scores were particularly good predictors of coronary heart disease. Atherosclerosis or thickening of the artery walls due to fatty substances is a major factor in heart disease and some forms of stroke. It has also been linked to lower IQ.

Obesity

Lower intelligence in childhood and adolescence correlates with an increased risk of obesity. One study found that a 15-point increase in intelligence score was associated with a 24% decrease in risk of obesity at age 51. The direction of this relationship has been greatly debated with some arguing that obesity causes lower intelligence, however, recent studies have indicated that a lower intelligence increases the chances of obesity.

Blood pressure

Higher intelligence in childhood and adulthood has been linked to lower blood pressure and a lower risk of hypertension.

Stroke

Strong evidence has been found in support of a link between intelligence and stroke, with those with lower intelligence being at greater risk of stroke. One study found visuospatial reasoning was the best predictor of stroke compared to other cognitive tests. Further this study found that controlling for socioeconomic variables did little to attenuate the relationship between visuospatial reasoning and stroke.

Cancer

Studies exploring the link between cancer and intelligence have come to varying conclusions. A few studies, which were mostly small have found an increased risk of death from cancer in those with lower intelligence. Other studies have found an increased risk of skin cancer with higher intelligence. However, on the whole most studies have found no consistent link between cancer and intelligence.

Psychiatric

Bipolar disorder and intelligence

Bipolar disorder is a mood disorder characterized by periods of elevated mood known as mania or hypomania and periods of depression. Anecdotal and biographical evidence popularized the idea that sufferers of bipolar disorder are tormented geniuses that are uniquely equipped with high levels of creativity and superior intelligence. Bipolar disorder is relatively rare, affecting only 2.5% of the population, as it is also the case with especially high intelligence. The uncommon nature of the disorder and rarity of high IQ pose unique challenges in sourcing large enough samples that are required to conduct a rigorous analysis of the association between intelligence and bipolar disorder. Nevertheless, there has been much progress starting from the mid-90s, with several studies beginning to shed a light on this elusive relationship.

One such study examined individual compulsory school grades of Swedish pupils between the ages of 15 and 16 to find that individuals with excellent school performance had a nearly four times increased rate to develop a variation of bipolar disorder later in life than those with average grades. The same study also found that students with lowest grades were at a moderately increased risk of developing bipolar disorder with nearly a twofold increase when compared to average-grade students.

A New Zealand study of 1,037 males and females from the 1972–1973 birth cohort of Dunedin suggests that lower childhood IQs were associated with an increased risk of developing schizophrenia spectrum disorders, major depression, and generalized anxiety disorder in adulthood; whereas higher childhood IQ predicted an increased likelihood of mania. This study only included eight cases of mania and thus should only be used to support already existing trends.

In the largest study yet published analyzing the relationship between bipolar disorder and intelligence, Edinburgh University researchers looked at the link between intelligence and bipolar disorder in a sample of over one million men enlisted in the Swedish army during a 22-year follow-up period. Regression results showed that the risk of hospitalization for bipolar disorder with comorbidity to other mental health illnesses decreased in a linear pattern with an increase in IQ. However, when researchers restricted the analysis to men without any psychiatric comorbidity, the relationship between bipolar disorder and intelligence followed a J-curve. 

Note: Illustrative graph only – not based on actual data points, but representative of established research on the relationship between IQ and Bipolar Disorders. Please refer to Gale for further information.

 

These findings suggest that men of extremely high intelligence are at a higher risk of experiencing bipolar in its purest form, and demands future investigation of the correlation between extreme brightness and pure bipolar.

Additional support of a potential association between high intelligence and bipolar disorder comes from biographical and anecdotal evidence, and primarily focus on the relationship between creativity and bipolar disorder. Doctor Kay Redfield Jamison has been a prolific writer on the subject publishing several articles and an extensive book analyzing the relationship between the artistic temperament and mood disorders. Although a link between bipolar disorder and creativity has been established, there is no confirming evidence suggesting any significant relationship between creativity and intelligence. Additionally, even though some of these studies suggest a potential benefit to bipolar disorder in regards to intelligence, there is significant amount of controversy as to the individual and societal cost of this presumed intellectual advantage. Bipolar disorder is characterized by periods of immense pain and suffering, self-destructive behaviors, and has one of the highest mortality rates of all mental illnesses.

Schizophrenia and cognition

Schizophrenia is chronic and disabling mental illness that is characterized by abnormal behavior, psychotic episodes and inability to recognize between reality and fantasy. Even though schizophrenia can severely handicap its sufferers, there has been a great interest in the relationship of this disorder and intelligence. Interest in the association of intelligence and schizophrenia has been widespread partly stems from the perceived connection between schizophrenia and creativity, and posthumous research of famous intellectuals that have been insinuated to have suffered from the illness. Hollywood played a pivotal role popularizing the myth of the schizophrenic genius with the movie A Beautiful Mind that depicted the life story of Nobel Laureate, John Nash and his struggle with the illness. 

Although stories of extremely bright schizophrenic individuals such as that of John Nash do exist, they are the outliers and not the norm. Studies analyzing the association between schizophrenia and intelligence overwhelmingly suggest that schizophrenia is linked to lower intelligence and decreased cognitive functioning. Since the manifestation of schizophrenia is partly characterized by cognitive and motor declines, current research focuses on understanding premorbid IQ patterns of schizophrenia patients.

In the most comprehensive meta-analysis published since the groundbreaking study by Aylward et al. in 1984, researchers at Harvard University found a medium-sized deficit in global cognition prior to the onset of schizophrenia. The mean premorbid IQ estimate for schizophrenia samples was 94.7 or 0.35 standard deviations below the mean, and thus at the lower end of the average IQ range. Additionally, all studies containing reliable premorbid and post-onset IQ estimates of schizophrenia patients found significant decline in IQ scores when comparing premorbid IQ to post-onset IQ. However, while the decline in IQ over the course of the onset of schizophrenia is consistent with theory, some alternative explanations for this decline suggested by the researchers include the clinical state of the patients and/or side effects of antipsychotic medications.

A recent study published in March 2015 edition of the American Journal of Psychiatry suggests that not only there is no correlation between high IQ and schizophrenia, but rather that a high IQ may be protective against the illness. Researchers from the Virginia Commonwealth University analyzed IQ data from over 1.2 million Swedish males born between 1951 and 1975 at ages 18 to 20 years old to investigate future risk of schizophrenia as a function of IQ scores. The researchers created stratified models using pairs of relatives to adjust for family clusters and later applied regression models to examine the interaction between IQ and genetic predisposition to schizophrenia. Results from the study suggest that subjects with low IQ were more sensitive to the effect of genetic liability to schizophrenia than those with high IQ and that the relationship between IQ and schizophrenia is not a consequence of shared genetic or familial-environmental risk factors, but may instead be causal.

Post-traumatic stress disorder and traumatic exposure

The Archive of General Psychiatry published a longitudinal study of a randomly selected sample of 713 study participants (336 boys and 377 girls), from both urban and suburban settings. Of that group, nearly 76 percent had suffered through at least one traumatic event. Those participants were assessed at age 6 years and followed up to age 17 years. In that group of children, those with an IQ above 115 were significantly less likely to have Post-Traumatic Stress Disorder as a result of the trauma, less likely to display behavioral problems, and less likely to experience a trauma. The low incidence of Post-Traumatic Stress Disorder among children with higher IQs was true even if the child grew up in an urban environment (where trauma averaged three times the rate of the suburb), or had behavioral problems.

Other disorders

Post-traumatic stress disorder, severe depression, and schizophrenia are less prevalent in higher IQ bands. Some studies have found that higher IQ persons show a higher prevalence of Obsessive Compulsive Disorder, but a 2017 meta study found the opposite, that people who suffered from OCD had slightly lower average IQs.

Substance abuse

Substance abuse is a patterned use of drug consumption in which a person uses substances in amounts or with methods that are harmful to themselves or to others. Substance abuse is commonly associated with a range of maladaptive behaviors that are both detrimental to the individual and to society. Given the terrible consequences that can transpire from abusing substances, recreational experimentation and/or recurrent use of drugs are traditionally thought to be most prevalent among marginalized strands of society. Nevertheless, the very opposite is true; research both in national and individual levels have found that the relationship between IQ and substance abuse indicates positive correlations between superior intelligence, higher alcohol consumption and drug consumption.

Note: Illustrative graph only – not based on actual data points, but accurate to trends previously established between alcohol consumption and national IQ. For actual data points please refer to Belasen and Hafer 2013 publication.

 

A significant positive association between worldwide national alcohol consumption per capita and country level IQ scores has been found.

The relationship between childhood IQ scores and illegal drugs use by adolescence and middle age has been found. High IQ scores at age 10 are positively associated with intake of cannabis, cocaine (only after 30 years of age), ecstasy, amphetamine and polydrug and also highlight a stronger association between high IQ and drug use for women than men. Additionally, these findings are independent of socio-economic status or psychological distress during formative years. A high IQ at age 11 was predictive of increased alcohol dependency later in life and a one standard deviation increase in IQ scores (15-points) was associated with a higher risk of illegal drug use.

The counterintuitive nature of the correlation between high IQ and substance abuse has sparked a fervent debate in the scientific community with some researchers attributing these findings to IQ being an inadequate proxy of intelligence, while others fault employed research methodologies and unrepresentative data. However, with the increased number of studies publishing similar results, overwhelming consensus is that the association between high IQ and substance abuse is real, statistically significant and independent of other variables.

There are several competing theories trying to make sense of this apparent paradox. Doctor James White postulates that people with higher IQs are more critical of information and thus less likely to accept facts at face value. While marketing campaigns against drugs may deter individuals with lower IQs from using drugs with disjoint arguments or over-exaggeration of negative consequences, people with a higher IQ will seek to verify the validity of such claims in their immediate environment. White also eludes to an often-overlooked problem of people with higher IQ, the lack of adequate challenges and intellectual stimulation. White posits that high IQ individuals that are not sufficiently engaged in their lives may choose to forgo good judgment for the sake of stimulation.

The most prominent theory attempting to explain the positive relationship between IQ and substance abuse; however, is the Savanna–IQ interaction hypothesis by social psychologist Satoshi Kanazawa. The theory is founded on the assumption that intelligence is a domain-specific adaptation that has evolved as humans moved away from the birthplace of human race, the savanna. Therefore, theory follows that as humans explored beyond the savannas, intelligence rather than instinct dictated survival. Natural selection privileged those who possessed high IQ while simultaneously favoring those with an appetite for evolutionary novel behaviors and experiences. For Kanazawa, this drive to seek evolutionary novel activities and sensations translates to being more open and callous about experimenting with and/or abusing substances in modern culture. For all the attention that the Savanna–IQ interaction hypothesis has garnered with the general public, this theory however, receives equal amounts of praise and criticism in the academic community with key pain points being the fact that humans have continued to evolve after moving away from the savannas and Kanazawa's misattribution of aspects of the openness personality trait to being indicative of superior general intelligence.

Dementia

A decrease in IQ has also been shown as an early predictor of late-onset Alzheimer's Disease and other forms of dementia. In a 2004 study, Cervilla and colleagues showed that tests of cognitive ability provide useful predictive information up to a decade before the onset of dementia.

However, when diagnosing individuals with a higher level of cognitive ability, a study of those with IQ's of 120 or more, patients should not be diagnosed from the standard norm but from an adjusted high-IQ norm that measured changes against the individual's higher ability level.

In 2000, Whalley and colleagues published a paper in the journal Neurology, which examined links between childhood mental ability and late-onset dementia. The study showed that mental ability scores were significantly lower in children who eventually developed late-onset dementia when compared with other children tested.

Health related behaviors

Alcohol

The relationship between alcohol consumption and intelligence is not straightforward. In some cohorts higher intelligence has been linked to a reduced risk of binge drinking. In one Scottish study higher intelligence was linked to a lower chance of binge drinking; however, units of alcohol consumed were not measured and alcohol induced hangovers in middle age were used as a proxy for binge drinking. Several studies have found the opposite effect with individuals of higher intelligence being more likely to drink more frequently, consume more units and have a higher risk of developing a drinking problem, especially in women.

Drugs

In U.S. study the link between drug intake and intelligence suggests that individuals with lower IQ take more drugs. However, in the UK the opposite relationship has been found with higher intelligence being related to greater illegal drug use.

Smoking

The relationship between intelligence and smoking has changed along with public and government attitudes towards smoking. For people born in 1921 there was no correlation between intelligence and having smoked or not smoked; however, there was a relationship between higher intelligence and quitting smoking by adulthood. In another British study, high childhood IQ was shown to inversely correlate with the chances of starting smoking.

Diet

One British study found that high childhood IQ was shown to correlate with one's chance of becoming a vegetarian in adulthood. Those of higher intelligence are also more likely to eat a healthier diet including more fruit and vegetables, fish, poultry and wholemeal bread and to eat less fried food.

Exercise

Higher intelligence has been linked to exercising. More intelligent children tend to exercise more as adults and to exercise vigorously.

A study of 11,282 individuals in Scotland who took intelligence tests at ages 7, 9 and 11 in the 1950s and 1960s, found an "inverse linear association" between childhood intelligence and hospital admissions for injuries in adulthood. The association between childhood IQ and the risk of later injury remained even after accounting for factors such as the child's socioeconomic background.

Socioeconomic status

Practically all indicators of physical health and mental competence favour people of higher socioeconomic status (SES). Social class attainment is important because it can predict health across the lifespan, where people from lower social class have higher morbidity and mortality. SES and health outcomes are general across time, place, disease, and are finely graded up the SES continuum. Gottfredson argues that general intelligence (g) is the fundamental cause for health inequality. The argument is that g is the fundamental cause of social class inequality in health, because it meets six criteria that every candidate for the cause must meet: stable distribution over time, is replicable, is a transportable form of influence, has a general effect on health, is measurable, and is falsifiable. 

Stability: Any casual agent has to be persistent and stable across time for its pattern of effects to be general over ages and decades. Large and stable individual differences in g are developed by adolescence and the dispersion of g in population's intelligence present in every generation, no matter what social circumstances are present. Therefore, equalizing socioeconomic environments does very little to reduce the dispersion in IQ. The dispersion of IQ in a society in general is more stable, than its dispersion of socioeconomic status.

Replicability: Siblings who vary in IQ also vary in socioeconomic success which can be comparable with strangers of comparable IQ. Also, g theory predicts that if genetic g is the principal mechanism carrying socioeconomic inequality between generations, then the maximum correlation between the parent and child SES will be near to their genetic correlation for IQ (.50). 

Transportability: The performance and functional literacy studies both illustrated how g is transportable across life situations and it represents a set of largely generalizable reasoning and problem-solving skills. G appear to be linearly linked to performance in school, jobs and achievements. 

Generality: Studies show that IQ measured at the age of 11 predicted longevity, premature death, lung and stomach cancers, dementia, loss of functional independence, more than 60 years later. Research has shown that higher IQ at age 11 is significantly related to higher social class in midlife. Therefore, it is safe to assume that higher SES, as well as higher IQ, generally predicts better health. 

Measurability: g factor can be extracted from any broad set of mental tests and has provided a common, reliable source for measuring general intelligence in any population.

Falsifiability: theoretically, if g theory would conceive health self-care as a job, as a set of instrumental tasks performed by the individuals, it could predict g to influence the health performance in the same way as it predicts performance in education and job. 

Chronic illnesses are the major illnesses in developed countries today, and their major risk factors are health habits and lifestyle. The higher social strata knows the most and the lower social strata knows the least, whether class is assessed by education, occupation or income and even when the information seems to be most useful for the poorest. Higher g promotes more learning, and it increases exposure to learning opportunities. So, the problem is not in the lack of access to health-care, but the patient's failure to use it effectively when delivered. Low literacy has been associated with low use of preventive care, poor comprehension of one's illness – even when care is free. Health self-management is important because literacy provides the ability to acquire new information and complete complex tasks and that limited problem solving abilities make low-literacy patients less likely to change their behaviour on the basis of new information. Chronic lack of good judgement and effective reasoning leads to chronically poor self-management.

Explanations of the correlation between intelligence and health

There have been many reasons posited for the links between health and intelligence. Although some have argued that the direction is one in which health has an influence on intelligence, most have focused on the influence of intelligence on health. Although health may definitely affect intelligence, most of the cognitive epidemiological studies have looked at intelligence in childhood when ill health is far less frequent and a more unlikely cause of poor intelligence. Thus most explanations have focused on the effects intelligence has on health through its influence on mediating causes. 

Various explanations for these findings have been proposed:

"First, ...intelligence is associated with more education, and thereafter with more professional occupations
that might place the person in healthier environments. ...Second, people with higher intelligence might engage in more healthy behaviours. ...Third, mental test scores from early life might act as a record of insults to the brain that have occurred before that date. ...Fourth, mental test scores obtained in youth might be an indicator of a well-put-together system. It is hypothesized that a well-wired body is more able to respond effectively to environmental insults..."

System integrity hypothesis vs evolution hypothesis

The System integrity hypothesis posits that childhood intelligence is just one aspect of a well wired and well-functioning body and suggests that there is a latent trait that encompasses intelligence, health and many other factors. This trait indexes how well the body is functioning and how well the body can respond to change and return to a normal balance again (allostatic load). According to the system integrity hypothesis lower IQ does not cause mortality but instead poor system integrity causes lower intelligence and poorer health as well as a range of other traits which can be thought of as markers of system integrity. Professor Ian Deary has proposed that fluctuating asymmetry, speed of information processing, physical co-ordination, physical strength, metabolic syndrome and genetic correlation may be further potential markers of system integrity which by definition should explain a large part of or nullify the relationship between intelligence and mortality. 

An opposing theory to the system integrity theory is the evolutionary novelty theory which suggests that those with higher intelligence are better equipped to deal with evolutionary novel events. It is proposed that intelligence evolved to tackle evolutionarily novel situations and that those with a higher IQ are better able to process when such a novel situation is dangerous or a health hazard and thus are likely to be in better health. This theory provides a theoretical background for evidence found that supports the idea that intelligence is related to mortality through health behaviours such as wearing a seatbelt or quitting smoking. Evolutionary novelty theory emphasises the role of behaviour in the link between mortality and intelligence whereas system integrity emphasis the role of genes. Thus system integrity predicts that individuals of higher intelligence will be better protected from diseases that are caused primarily by genetics whereas evolutionary adaptive theory suggests that individuals of higher intelligence will be better protected from diseases that are less heritable and are caused by poor life choices. One study which tested this idea looked at the incidence of heritable and non-heritable cancers in individuals of differing levels of intelligence. They found that those of higher intelligence were less likely to suffer from cancer that was not heritable, that was based on lifestyle, thus supporting the evolutionary novelty theory. However this was only a preliminary study and only included the disease cancer, which has been found in previous studies to have an ambiguous relationship with intelligence.

Disease and injury prevention

Having higher intelligence scores may mean that individuals are better at preventing disease and injury. Their cognitive abilities may equip them with a better propensity for understanding the injury and health risks of certain behaviours and actions. Fatal and non-fatal accidental injury have been associated with lower intelligence. This may be because individuals of higher intelligence are more likely to take precautions such as wearing seat belts, helmets etc. as they are aware of the risks. 

Further there is evidence that more intelligent people behave in a healthier way.

People with higher IQ test scores tend to be less likely to smoke or drink alcohol heavily. They also eat better diets, and they are more physically active. So they have a range of better behaviours that may partly explain their lower mortality risk.

— -Dr. David Batty

Individuals with higher cognitive abilities are also better equipped for dealing with stress, a factor that has been implemented in many health problems ranging from anxiety to cardiovascular disease. It has been suggested that higher intelligence leads to a better sense of control over one's own life and a reduction in feelings of stress. One study found that individuals with lower intelligence experienced a greater number of functional somatic symptoms, symptoms that cannot be explained by organic pathology and are thought to be stress related. However most of the relationship was mediated by work conditions.

Disease and injury management

There is evidence that higher intelligence is related to better self-care when one has an illness or injury. One study asked participants to take aspirin or a placebo on a daily basis during a study on cardiovascular health. Participants with higher intelligence persisted with taking the medication for longer than those with lower intelligence indicating that they could care for themselves better. Studies have shown that individuals with lower intelligence have lower health literacy and a study looking at the link between health literacy and actual health found that it was mediated almost entirely by intelligence. It has been claimed that up to a third of medications are not taken correctly and thus jeopardize the patients' health. This is particularly relevant for those with heart problems as the misuse of some heart medications can actually double the risk of death. More intelligent individuals also make use of preventative healthcare more often for example visiting the doctors. Some have argued however that this is an artefact of higher SES; that those with lower intelligence tend to be from a lower social class and have less access to medical facilities. However it has been found that even when access to healthcare is equal, those with lower intelligence still make less use of the services.

Psychiatric illness

A diagnosis of any mental illness, even mild psychological distress, is linked to an increased risk of illness and premature death. The majority of psychiatric illness' are also linked to lower intelligence. Thus it has been proposed that psychiatric morbidity may be another pathway through which intelligence and mortality are related. Despite this the direction of causation between Intelligence and mental health issues has been disputed. Some argue that mental health issues such as depression and schizophrenia may cause a decline in mental functioning and thus scores on intelligence tests whilst others believe that it is lower intelligence that effects likelihood of developing a mental health issue. Although evidence for both points of view has been found, most of the cognitive epidemiological studies are carried out using intelligence scores from childhood, when the psychiatric condition was not present, ensuring that it was not the condition which caused the lower scores. This link has been shown to explain part of the relationship between childhood intelligence and mortality, however the amount of variance explained varies from less than 10 percent to about 5 percent.

Socioeconomic position in adulthood

Although childhood economic status may be seen as a confounder in the relationship between intelligence and mortality, as it is likely to affect intelligence, it is likely that adult SES mediates the relationship. The idea is that intelligent children will find themselves getting a better education, better jobs and will settle in a safer and healthier environment. They will have better access to health resources, good nutrition and will be less likely to experience the hazards and health risks associated with living in poorer neighbourhoods. Several studies have found that there is an association between adult SES and mortality.

Proposed general fitness factor of both cognitive ability and health, the f-factor

Because of the above-mentioned findings, some researchers have proposed a general factor of fitness analogous to the g-factor for general mental ability/intelligence. This factor is supposed to combine fertility factors, health factors, and the g-factor. For instance, one study found a small but significant correlation between three measures of sperm quality and intelligence.