Etiology of longitudinal associations between subjective effects and substance use disorders in a clinical sample.

Background: Subjective effects (SEs) are positively associated with substance use disorders in clinical samples. However, the etiology of these associations remains unclear. The present study utilized a clinical sample selected for elevated polysubstance use disorder (SUD) criteria to address the following questions: Are positive and negative polysubstance SEs and SUD criteria associated? Are cross-sectional and longitudinal results consistent? Is there evidence for common genetic influences between SEs and SUDs? Methods: Cross-sectional and longitudinal analyses using the Defries Fulker regression method were conducted in clinical probands (n = 476) and their full (n = 557) and half siblings (n = 65). SEs were assessed in adolescence and SUD criteria were assessed once in adolescence and twice in adulthood. Results: SEs were correlated with SUD criteria from adolescence to adulthood in clinical probands (r = 0.12-0.40) and during adolescence (r = 0.36-0.39) in full siblings of clinical probands. Results were inconsistent with common genetic influences between elevated SUDs and SEs. Conclusions: Elevated SUDs and SEs were mostly explained by familial influences independent of genetics. There was little support for common genetic influences on elevated SUDs and SEs, possibly due to low power. Future research should focus on individual factors driving associations between these constructs.