Association Between Medical Diagnoses and Suicide in a Medicaid Beneficiary Population, North Carolina 2014-2017

Background: Firearms are used in about half of U.S. suicides. This study investigated how various medical diagnoses are associated with firearm and nonfirearm suicide. Methods: We used a case control design including n = 691 North Carolina Medicaid beneficiaries who died from suicide between 1 January 2014 and 31 December 2017 as cases. We selected a total of n = 68,682 controls (similar to 1:100 case-control ratio from North Carolina Medicaid member files using incidence density sampling methods). We linked Medicaid claims to the North Carolina Violent Death Reporting System to ascertain suicide and means (firearm or nonfirearm). We matched cases and controls on number of months covered by Medicaid over the past 36 months. Analyses adjusted for sex, race, age, Supplemental Security Income status, the Charlson Comorbidity Index, and frequency of health care encounters. Results: The case control odds ratios for any mental health disorder were 4.2 (95% confidence interval [CI]: 3.3, 5.2) for nonfirearm suicide and 2.2 (95% CI: 1.7, 2.9) for firearm suicide. There was effect measure modification by sex and race. Behavioral health diagnoses were more strongly associated with nonfirearm suicides than firearm suicide in men but did not differ substantially in women. The association of mental health and substance use diagnoses with suicides appeared to be weaker in Blacks (vs. non-Blacks), but the estimates were imprecise. Conclusion: Behavioral health diagnoses are important indicators of risk of suicide. However, these associations differ by means of suicide and sex, and associations for firearm-related suicide are weaker in men than women.