Further evidence linking suicide risk to family history (p 1126)

A Danish study in this week's issue of THE LANCET provides further evidence linking a family history of psychiatric illness and suicide to increased suicide risk--the study also shows how a family history of suicide and psychiatric illness act independently and are not influenced by socio-economic factors.

Previous research has highlighted a clustering of suicidal behaviour among families. Ping Qin and colleagues from Aarhus University, Denmark, assessed whether family history of completed suicide and mental illness that results in admission to hospital were risk factors for suicide, and whether these factors interact.

Using data from four Danish longitudinal registers, the investigators identified 4262 people who had committed suicide aged 9–45 years during 1981–97, and 80,238 matched controls.

Individuals with a history of family suicide were two and a half times more likely to commit suicide than people without a family history of suicide; correspondingly, a family history of psychiatric illness (requiring hospital admission) increased suicide risk by around 50%, but only for individuals who did not have a psychiatric history. A history of family suicide and psychiatric history were independent risk factors for suicide, but the effect was strongest when they were combined.

Ping Qin comments: "With respect to attributable risk, we have shown that a family suicide history and family psychiatric history accounted for 2.25% and 6.80% of suicides, respectively. These estimates were made after adjustment for other risk factors and would be larger if exposures in other relatives, family history of suicide attempts, and family history of psychiatric disorders that did not result in admission to hospital had been included."

She concludes: "The inclusion of familial suicidal history in the assessment of suicide risk is important, even though people with a family history of suicide are only a small proportion of the total number of people who commit suicide. Also, the importance of family psychiatric history should not be disregarded, because it can help to identify people vulnerable to mental disorders associated with suicide. These factors might be essential in prevention programmes targeting adolescents and young adults, and might apply to the general population."

Contact: Dr Ping Qin, National Center for Register-based Research, Aarhus University, Taasingegade 1,DK-8000 Aarhus C, Denmark; T) +45 8942 6803; F) +45 8942 6813; E) pq@ncrr.dk

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