Background. Clinical judgments about the likelihood of suicide attempt would be aided by an index of risk factors that could be quickly assessed in diverse settings. We sought to develop such a risk index for 12-month suicide attempts among suicide ideators.

Method. The National Comorbidity Survey Replication (NCS-R), a household survey of adults aged 18+, assessed the 12-month occurrence of suicide ideation, plans and attempts in a subsample of 5692 respondents. Retrospectively assessed correlates include history of prior suicidality, sociodemographics, parental psychopathology and 12-month DSM-IV disorders.

Results. Twelve-month prevalence estimates of suicide ideation, plans and attempts are 2·6, 0·7 and 0·4% respectively. Although ideators with a plan are more likely to make an attempt (31·9%) than those without a plan (9·6%), 43% of attempts were described as unplanned. History of prior attempts is the strongest correlate of 12-month attempts. Other significant correlates include shorter duration of ideation, presence of a suicide plan, and several sociodemographic and parental psychopathology variables. Twelve-month disorders are not powerful correlates. A four-category summary index of correlates is strongly related to attempts among ideators [area under the receiver operator characteristic curve (AUC)=0·88]. The distribution (conditional probability of attempt) of the risk index is: 19·0% very low (0·0%), 51·1% low (3·5%), 16·2% intermediate (21·3%), and 13·7% high (78·1%). Two-thirds (67·1%) of attempts were made by ideators in the high-risk category.

Conclusions. A short, preliminary risk index based on retrospectively reported responses to fully structured questions is strongly correlated with 12-month suicide attempts among ideators, with a high concentration of attempts among high-risk ideators.