Abstract
BACKGROUND: Adolescent substance use (SU) is often motivated by a desire to alleviate undesirable symptoms. To test the self-medication hypothesis, we examined associations between comorbid psychologic and somatic symptom trajectories across early adolescence and early onset SU. METHODS: Using Adolescent Brain Cognitive Development Study® data, we differentiated youth who reported no SU at baseline based on their comorbid anxiety, depression, pain, somatic and somnolence symptom trajectories. The outcome, early onset SU (by age 13-14 years) was derived from self-reported alcohol (≥full drink), tobacco (full regular/e-cigarette), marijuana, or other drug use over 5 years. RESULTS: 8311 participants were classified with Asymptomatic (27.8 %), Low/stable (39 %), Moderate/persistent (25.3 %) or High/worsening trajectories (7.9 %) from age 9.97 ± 0.74 to 13.57 ± 0.88 years. Early onset SU was 56 % higher for Moderate-High compared to Asymptomatic-Low symptom trajectory groups (12.5 % vs. 8.5 %; OR 1.56 [95 % CI 1.33, 1.79]). Adjusted for covariates, the High/worsening group was more likely than the Asymptomatic group to report use of any substance (adj.OR 2.13 [95 % CI 1.40, 3.25], Alcohol (adj.OR 2.80 [95 % CI 1.56, 5.02]), Tobacco (adj.OR 2.09 [95 % CI 1.23, 3.55]), and Marijuana (adj.OR 2.33 [95 % CI 1.36, 3.99]). Longitudinal, time-lagged analyses revealed potential feedback effects of earlier depression on subsequent SU, and earlier SU on later depression (p < 0.001). CONCLUSION: Higher comorbid symptom trajectories emerging in late childhood increased the likelihood of early onset SU. Since negative feedback loops may contribute to symptom persistency, ongoing and potentially harmful SU for at-risk youth, addressing comorbid symptoms that emerge during late childhood is warranted.