Age-varying associations between substance use behaviors and depressive symptoms during adolescence and young adulthood.
BACKGROUND
Substance use and depression often co-occur, complicating treatment of both substance use and depression. Despite research documenting age-related trends in both substance use and depression, little research has examined how the associations between substance use behaviors and depression changes across the lifespan.


METHODS
This study examines how the associations between substance use behaviors (daily smoking, regular heavy episodic drinking (HED), and marijuana use) and depressive symptoms vary from adolescence into young adulthood (ages 12-31), and how these associations differ by gender. Using data from the National Longitudinal Study of Adolescent to Adult Health (Add Health), we implemented time-varying effect models (TVEM), an analytic approach that estimates how the associations between predictors (e.g., substance use measures) and an outcome (e.g., depressive symptoms) vary across age.


RESULTS
Marijuana use and daily smoking were significantly associated with depressive symptoms at most ages from 12 to 31. Regular HED was significantly associated with depressive symptoms during adolescence only. In bivariate analyses, the association with depressive symptoms for each substance use behavior was significantly stronger for females at certain ages; when adjusting for concurrent substance use in a multivariate analysis, no gender differences were observed.


CONCLUSIONS
While the associations between depressive symptoms and both marijuana and daily smoking were relatively stable across ages 12-31, regular HED was only significantly associated with depressive symptoms during adolescence. Understanding age and gender trends in these associations can help tailor prevention efforts and joint treatment methods in order to maximize public health benefit.
Department of Health Care Policy, Harvard Medical School, Boston, MA 02215, United States. Electronic address: schuler@hcp.med.harvard.edu.
Megan S
MS
Schuler
The Methodology Center, The Pennsylvania State University, State College, PA 16801, United States. Electronic address: sav141@psu.edu.
Sara A
SA
Vasilenko
The Methodology Center, Department of Biobehavioral Health, The Pennsylvania State University, State College, PA 16801, United States. Electronic address: slanza@psu.edu.
Stephanie T
ST
Lanza
D000293:Adolescent; D000328:Adult; D000375:Aging / Q000523:psychology*; D000428:Alcohol Drinking / Q000523:psychology*; D002648:Child; D003863:Depression / Q000150:complications / Q000523:psychology*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008385:Marijuana Smoking / Q000523:psychology*; D012727:Sex Characteristics; D012907:Smoking / Q000523:psychology*; D055815:Young Adult
Adolescence; Age-varying effects; Comorbidity; Depression; Substance use; Young adulthood