Advertisement

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
  • David Gunnell
  • Roger Harbord
  • Nicola Singleton
  • Rachel Jenkins
  • Glyn Lewis
ORIGINAL PAPER

Abstract

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.

Aim

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

Method

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).

Conclusion

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.

Keywords

IQ NART suicidal thoughts cohort 

Notes

Acknowledgments

We would like to thank Howard Meltzer for initial design work on the survey and other ONS staff who were involved in the fieldwork and data preparation. Contributors: The Office for National Statistics carried out the longitudinal study on which this paper is based. NS was Project Manager for the study with responsibility for the data collection, analysis and reporting of the study as a whole. DG conceived and wrote the first draft of the paper and will act as guarantor, RH conducted the analyses and all authors commented on, and contributed to, revisions of the paper. GL and RJ contributed to the design and analysis of the study and provided critical comments on the manuscript. All authors have approved the final version of the paper. Funding: The data collection was funded by the Department of Health and the Scottish Executive Health Department. The views expressed in this report are those of the authors and not the Department of Health. Ethical approval: Ethical approval for the survey work was obtained from the London MREC. Competing interests: None

References

  1. 1.
    Alaraisanen A, Miettunen J, Lauronen E, Rasanen P, Isohanni M (2006) Good school performance is a risk factor of suicide in psychoses: a 35-year follow up of the Northern Finland 1966 birth cohort. Acta Psychiatr Scand 114:357–362PubMedCrossRefGoogle Scholar
  2. 2.
    Allebeck P, Allgulander D, Fisher LD (1988) Predictors of completed suicide in a cohort of 50,465 young men: role of personality and deviant behaviour. BMJ 297:176–178PubMedGoogle Scholar
  3. 3.
    Andersson L, Allebeck P, Gustafsson J-E, Gunnell D (2008) Association of IQ scores and school achievement with suicide in a 40-year follow-up of a Swedish cohort doi:  10.1111/j.1600-0447.2008.01171.x
  4. 4.
    Crawford JR, Parker DM, Allan KM, Jack AM, Morrison FM (1991) The short NART: cross-validation, relationship to IQ and some practical considerations. Br J Clin Psychol 30(Pt 3):223–229PubMedGoogle Scholar
  5. 5.
    Crawford JR, Parker DM, Stewart LE, Besson JAO, De Lacey G (1989) Prediction of WAIS IQ with the national adult reading test: cross-validation and extension. Br J Clin Psychol 28:267–273Google Scholar
  6. 6.
    David AS, Malmberg A, Brandt L, Allebeck P, Lewis G (1997) IQ and risk for schizophrenia: a population-based cohort study. Psychol Med 27:1311–1323PubMedCrossRefGoogle Scholar
  7. 7.
    Fanous AH, Prescott CA, Kendler KS (2004) The prediction of thoughts of death or self-harm in a population-based sample of female twins. Psychol Med 34:301–312PubMedCrossRefGoogle Scholar
  8. 8.
    Fergusson DM, Horwood LJ, Ridder EM (2005) Show me the child at seven II: childhood intelligence and later outcomes in adolescence and young adulthood. J Child Psychol Psychiatry 46:850–858PubMedCrossRefGoogle Scholar
  9. 9.
    Gunnell D, Harbord R, Singleton N, Jenkins R, Lewis G (2004) Factors influencing the development and amelioration of suicidal thoughts in the general population. Cohort study. Br J Psychiatry 185:385–393PubMedCrossRefGoogle Scholar
  10. 10.
    Gunnell D, Harrison G, Rasmussen F, Fouskakis D, Tynelius P (2003) Associations between pre-morbid intellectual performance, early-life exposures and early-onset of schizophrenia. Br J Psychiatry 181:298–305CrossRefGoogle Scholar
  11. 11.
    Gunnell D, Magnusson PK, Rasmussen F (2005) Low intelligence test scores in 18 year old men and risk of suicide: cohort study. BMJ 330:167–170PubMedCrossRefGoogle Scholar
  12. 12.
    Hintikka J, Pesonen T, Saarinen P, Tanskanen A, Lehtonen J, Viinamaki H (2001) Suicidal ideation in the Finnish general population. A 12-month follow-up study. Soc Psychiatry Psychiatr Epidemiol 36:590–594PubMedCrossRefGoogle Scholar
  13. 13.
    Kessler RC, Borges G, Walters EE (1999) Prevalence of and risk factors for lifetime suicide attempts in the national comorbidity survey. Arch Gen Psychiatry 56:617–626PubMedCrossRefGoogle Scholar
  14. 14.
    Lewis G, Pelosi AJ (1990) Manual of the revised clinical interview schedule. CIS-R. Institute of Psychiatry, LondonGoogle Scholar
  15. 15.
    Lewis G, Pelosi AJ, Araya R, Dunn G (1992) Measuring psychiatric disorder in the community: a standardized assessment for use by lay interviewers. Psychol Med 22:465–486PubMedGoogle Scholar
  16. 16.
    Nelson HE, O’Connell A (1978) Dementia: the estimation of pre-morbid intelligence levels using the new adult reading test. Cortex 14:234–244PubMedGoogle Scholar
  17. 17.
    Nelson H, O’Connell A (1991) National adult reading test (NART) test manual. NFER-Nelson, WindsorGoogle Scholar
  18. 18.
    O’Toole BI, Cantor C (1995) Suicide risk factors among Australian Vietnam era draftees. Suicide Life Threat Behav 25:475–488PubMedGoogle Scholar
  19. 19.
    O’Toole BI, Stankov L (1992) Ultimate validity of psychological tests. Pers Individ Dif 13:699–716CrossRefGoogle Scholar
  20. 20.
    Paykel ES, Myers JK, Lindenthal JJ, Tanner J (1974) Suicidal feelings in the general population: a prevalence study. Br J Psychiatry 124:460–469PubMedCrossRefGoogle Scholar
  21. 21.
    Singleton N, Bumpstead R, O’Brien M, Lee A, Meltzer H (2001) Office of national statistics psychiatric morbidity among adults living in private households, 2000. HMSO, LondonGoogle Scholar
  22. 22.
    Singleton N, Lewis G (2003) Better or worse: a longitudinal study of the mental health of adults living in private households in Great Britain. The Stationary Office, LondonGoogle Scholar
  23. 23.
    Stata Corporation (2005) Intercooled stata 9.0 for windows. Stata Corporation, TexasGoogle Scholar
  24. 24.
    Van Os J, Jones P, Lewis G, Wadsworth M, Murray R (1997) Developmental precursors of affective illness in a general population birth cohort. Arch Gen Psychiatry 54:625–631PubMedGoogle Scholar
  25. 25.
    Voracek M (2004) National intelligence and suicide rate: an ecological study of 85 countries. Pers Individ Dif 37:543–553CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • David Gunnell
    • 1
  • Roger Harbord
    • 1
  • Nicola Singleton
    • 2
  • Rachel Jenkins
    • 3
  • Glyn Lewis
    • 4
  1. 1.Dept. of Social MedicineUniversity of BristolBristolUK
  2. 2.Social Survey DivisionOffice for National StatisticsLondonUK
  3. 3.WHO Collaborating Centre, Institute of PsychiatryLondonUK
  4. 4.Division of PsychiatryUniversity of BristolBristolUK

Personalised recommendations