Prior injury and motor vehicle crash as risk factors for youth suicide.

We conducted a case-control study to determine whether adolescents and young adults who have been in a motor vehicle crash or hospitalized for unintentional and intentional injury are at greater risk for suicide. Cases were 700 Washington State residents age 16-35 with a driver's license who died of suicide during 1987-1989. Controls were 3,494 licensed drivers matched by age, sex, and zip code. Using two different databases, we were able to determine the past incidence of in-state injury hospitalizations and motor vehicle crashes for all subjects. Overall, the incidence of suicide was tenfold higher among those with a past hospitalization for injury. Many of these admissions were for suicide attempts [odds ratio (OR) = 56, 95% confidence interval (CI) = 27-120], but the risk of suicide was also higher among those hospitalized for unintentional injuries (OR = 5.0, 95% CI = 2.2-11.5) and assaults (OR = 4.5, 95% CI = 1.1-18). The relative risk for suicide was 2.7 (95% CI = 2.0-3.5) for those with prior injury as a driver in a motor vehicle crash and 2.9 (95% CI = 2.2-3.8) for those with involvement in a single vehicle crash. Many unintentional injury hospitalizations and a proportion of motor vehicle crashes in younger adults may represent unrecognized suicide attempts.