Background. Few studies have examined the extent to which populations of suicides and attempted suicides are similar, or different. This paper compares suicides and serious suicide attempts in terms of known risk factors for suicidal behaviour.

Methods. Using case–control methodology, risk factors for suicidal behaviour were examined in 202 individuals who died by suicide, 275 individuals who made medically serious suicide attempts and 984 randomly selected control subjects. Based on data from significant others, measures used spanned sociodemographic factors, childhood experiences, psychiatric morbidity and psychiatric history, exposure to recent stressful life events and social interaction.

Results. Multiple logistic regression identified the following risk factors that were common to suicide and serious suicide attempts: current mood disorder; previous suicide attempts; prior out-patient psychiatric treatment; admission to psychiatric hospital within the previous year; low income; a lack of formal educational qualifications; exposure to recent stressful interpersonal, legal and work-related life events. Suicides and suicide attempts were distinguished in the following ways: suicides were more likely to be male (OR = 1·9, 95% CI 1·1, 3·2); older (OR = 1·03, 95% CI 1·02, 1·04); and to have a current diagnosis of non-affective psychosis (OR = 8·5, 95% CI 2·0, 35·9). Suicide attempts were more likely than suicides to have a current diagnosis of anxiety disorder (OR = 3·5, 95% CI 1·6, 7·8) and to be socially isolated (OR = 2·0, 95% CI 1·2, 3·5). These findings were confirmed by discriminant function analysis, which identified two functions that described the three subject groups: the first function discriminated the two suicide groups from control subjects on a dimension corresponding to risk factors for suicide; the second function discriminated suicide from suicide attempt subjects on a series of factors including gender, non-affective psychosis and anxiety disorder.

Conclusions. Suicides and medically serious suicide attempts are two overlapping populations that share common psychiatric diagnostic and history features, but are distinguished by gender and patterning of psychiatric disorder.