This study examined the trajectories of alcohol use, cannabis use, suicide planning (SP), and nonsuicidal self-injury (NSSI) prior to hospitalization and examined the role of alcohol and cannabis use, independently and jointly, in predicting NSSI on a daily level and over time.
Participants included 71 adolescents hospitalized for suicide risk (75% female; 25% male; Mage = 15.79). All participants drank alcohol at least once in the prior 90-days. We conducted mixed effect models to assess the trajectories of alcohol use, cannabis use, and NSSI over the 90-days prior hospitalization. To test the effect of SP, alcohol use, and cannabis use on NSSI, we conducted logistic random effect models, while controlling for demographics.
SP (OR = 4.47, p < 0.001) and suicide ideation (SI) (OR = 10.09, p < 0.001) significantly increased the odds of engaging in NSSI. Neither cannabis nor alcohol use independently predicted the odds of engaging in NSSI, however, the co-occurrence of alcohol and cannabis use increased the odds of engaging in NSSI on a given day (OR = 30.5, p < 0.05).
Study findings extend current knowledge about the longitudinal and day-to-day relationships between alcohol and cannabis use and NSSI. Results underscore the importance of developing interventions that address polysubstance use among suicidal adolescents engaging in NSSI.