Is low IQ associated with an increased risk of developing suicidal thoughts? A cohort study based on an 18-month follow-up of the national psychiatric morbidity survey.
BACKGROUND
Studies in young male conscripts suggest that low IQ scores are associated with an increased risk of suicide. Mechanisms underlying this association are unclear.


OBJECTIVE
To investigate the association of IQ, as indexed by the national adult reading test (NART), with the incidence of, and recovery from, suicidal thoughts.


METHODS
An 18-month follow-up of 2,278 of the adults who took part in the Britain's second national psychiatric morbidity survey who completed the NART at baseline.


RESULTS
There was no evidence that poor performance on the NART was associated with an increased incidence of suicidal thoughts over the 18 month follow-up (adjusted odds ratio per 10 unit increase in NART-IQ 1.08 (95% CI 0.86-1.36). However, amongst the 155 subjects with suicidal thoughts at baseline, those with low NART-IQ were least likely to recover from them: the adjusted odds of recovery per 10 unit increase in NART-IQ was 1.42 (95% CI 0.96-2.10).


CONCLUSIONS
The association between low IQ and an increased risk of suicide may be because people with low IQ experience suicidal thoughts for more prolonged periods than those with high IQ or because low IQ increase the likelihood that people experiencing suicidal thoughts act upon them.
Gunnell
David
D
Department of Social Medicine, University of Bristol, Bristol, BS8 2PR, UK. d.j.gunnell@bristol.ac.uk
Harbord
Roger
R
Singleton
Nicola
N
Jenkins
Rachel
R
Lewis
Glyn
G
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D006306:Health Surveys; D006801:Humans; D007360:Intelligence; D016014:Linear Models; D008297:Male; D001523:Mental Disorders / Q000453:epidemiology / Q000523:psychology; D008875:Middle Aged; D019989:Persons with Intellectual Disabilities / Q000523:psychology*; D017678:Sex Distribution; D012959:Socioeconomic Factors; D013405:Suicide / Q000523:psychology*; D013997:Time Factors; D006113:United Kingdom / Q000453:epidemiology; D055815:Young Adult