SUICIDAL-BEHAVIOR - AN EPIDEMIOLOGIC AND GENETIC-STUDY

Background. Psychiatric history, familial history of suicide attempts, and certain traumatic life events are important predictors of suicida l thoughts and behaviour. We examined the epidemiology and genetics of suicidality (i.e. reporting persistent suicidal thoughts or a plan or suicide attempt) in a large community-based sample of MZ and DZ twin pairs. Method. Diagnostic telephone interviews were conducted in 1992- 3 with twins from an Australian twin panel first surveyed in 1980-82 ( N = 5995 respondents). Data were analysed using logistic regression mo dels, taking into account twin pair zygosity and the history of suicid ality in the respondent's co-twin. Results. Lifetime prevalence of sui cidal thoughts and attempts was remarkably constant across birth cohor ts 1930-1964, and across gender. Major psychiatric correlates were his tory of major depression, panic disorder, social phobia in women, alco hol dependence and childhood conduct problems. Traumatic events involv ing assault (childhood sexual abuse, rape or physical assault) or stat us-loss (job loss, loss of property or home, divorce), and the persona lity trait neuroticism, were also significantly associated with suicid e measures. Prevalence of serious suicide attempts varied as a functio n of religious affiliation. After controlling for these variables, how ever, history of suicide attempts or persistent thoughts in the respon dent's co-twin remained a powerful predictor in MZ pairs (odds ratio = 3.9), but was not consistently predictive in DZ pairs. Overall, genet ic factors accounted for approximately 45 % of the variance in suicida l thoughts and behaviour (95 % confidence interval 33-51 %). Conclusio ns. Risk of persistent suicidal thoughts and suicide attempts is deter mined by a complex interplay of psychiatric history, neuroticism, trau matic life experiences, genetic vulnerability specific for suicidal be haviour and sociocultural risk or protective factors.