An
association has been shown between bad
performance on cognition tests and enhanced risk
of depression and psychosis. The rare studies
that have examined the influence of the
intelligence level on suicide have produced
conflicting results. Recently a new study
investigated the association between
intelligence scores in men and subsequent
suicide.
987 308 men tested at age 18, were followed for
5-26 years and suicide was the main outcome
measure. Four intelligence tests covering
logic/general intelligence, verbal test of
synonym detection, test of
visuospatial/geometric perception, and
technical/mechanical skills with
mathematical/physics problems were performed.
Due to the duration of the analysis, results
from these tests were standardised to give
scores from 1 (low) to 9 (high) for each of the
four scales,.
During follow up 2811 suicides
occurred. The risk of suicide was 2 to 3
times higher in the subjects with lowest test
scores compared with those with the highest test
scores. The strongest association was observed
with the logic test in which for each unit
increase in test score reduced the risk by
suicide decreased by 12%. Surprisingly, the
highest risk was detected among subjects with
low test scores and highly educated parents. Men
with psychiatric disorders at baseline tended to
perform poorly on the tests, however, exclusion
of these individuals did not influence the
association between intelligence and
suicide.
Impaired neurodevelopment during childhood
results in increased susceptibility to mental
illness and low cognitive ability leading to
poor ability to solve problems during times of
life crisis, and psychosocial maladjustment in
childhood leading to poor school
performance. These are all possible factors
that may increase the risk of suicide. Gunnell
D, Magnusson PK, Rasmussen F. Low intelligence
test scores in 18 year old men and risk of
suicide: cohort study. BMJ 2005, 330:
167-171.