Background. Suicide is a leading cause of death worldwide but information about it is sparse in Sub-Saharan Africa. Suicide-related behaviours can provide an insight into the extent of this compelling consequence of mental illness.

Method. Face-to-face interviews were conducted with a representative sample of persons aged 18 years and over (n=6752) in 21 of Nigeria's 36 states (representing about 57% of the national population). Suicide-related outcomes, mental disorders, as well as history of childhood adversities were assessed using the World Health Organization (WHO) Composite International Diagnostic Interview (CIDI).

Results. Lifetime prevalence estimates of suicide ideation, plan and attempts were 3·2% [95% confidence interval (CI) 1·4–6·5], 1·0% (95% CI 0·4–7·5) and 0·7% (95% CI 0·5–1·0) respectively. Almost two of every three ideators who made a plan went on to make an attempt. The highest risks for transition from ideation to plan and from plan to attempt were in the first year of having ideation or plan respectively. Mental disorders, especially mood disorders, were significant correlates of suicide-related outcomes. Childhood adversities of long separation from biological parents, being raised in a household with much conflict, being physically abused, or being brought up by a woman who had suffered from depression, anxiety disorder, or who had attempted suicide were risk factors for lifetime suicide attempt.

Conclusions. History of childhood adversities and of lifetime mental disorders identify persons at high-risk for suicide-related outcomes. Preventive measures are best delivered within the first year of suicide ideation being expressed.