Cognitive epidemiology
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.
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.
Long term sick leave in adulthood has been shown to be related to lower cognitive abilities,[18] as has likelihood of receiving a disability pension.
One study found that low verbal, visuospatial and arithmetic scores were particularly good predictors of coronary heart disease.
[21] Atherosclerosis or thickening of the artery walls due to fatty substances is a major factor in heart disease and some forms of stroke.
Anecdotal and biographical evidence popularized the idea that those with bipolar disorder are tormented geniuses that are uniquely equipped with high levels of creativity and superior intelligence.
[33] 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.
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.
[35] 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.
[37] 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.
[38] Schizophrenia is chronic and disabling mental illness that is characterized by abnormal behavior, psychotic episodes and inability to distinguish between reality and fantasy.
[39] 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.
[citation needed] Although stories of extremely bright individuals with schizophrenia such as that of John Nash do exist, they are the outliers and not the norm.
[40] In the most comprehensive meta-analysis published since the groundbreaking study by Aylward et al. in 1984,[41] researchers at Harvard University found a medium-sized deficit in global cognition prior to the onset of schizophrenia.
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.
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.
[54][55][56] 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.
Doctor James White postulates that people with higher IQs are more critical of information and thus less likely to accept facts at face value.
White also alludes to an often-overlooked problem of people with higher IQ, the lack of adequate challenges and intellectual stimulation.
[58] 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.
[59] The most prominent[citation needed] theory attempting to explain the positive relationship between IQ and substance abuse; however, is the Savanna–IQ interaction hypothesis by social psychologist Satoshi Kanazawa.
[60] 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.
[citation needed] 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.
In 2000, Whalley and colleagues published a paper in the journal Neurology, which examined links between childhood mental ability and late-onset dementia.
[citation needed] Stability: Any casual agent has to be persistent and stable across time for its pattern of effects to be general over ages and decades.
Generality: Studies[79] 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.
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.
