The onset of substance use is a strong predictor of substance use disorders and related problems. This study examined the differences between early- and late-onset substance use in personality and substance use characteristics, traumatic experiences, and social support with a sample of 100 Turkish adults with substance use disorders. Early onset (<18 years) was associated with more traumatic experiences, increased risk of developing posttraumatic stress disorder (PTSD), and higher levels of depressive symptoms compared to late onset (≥18 years). Also, depressive symptoms, living, and working status were predictors of substance use onset. The study addresses the groups at risk of initiating substance use.
