Background and aims: The transdiagnostic Syndrome Model of Addiction considers addiction as a syndrome with multiple opportunities for expression, i.e., a common underlying disorder that may manifest in distinctive ways. Considering that testing of the model has been rare, this study examined the co-occurrence of symptoms of substance use disorders and behavioral addictions over 10 years by identifying profiles and predictors associated with group membership. Methods: Longitudinal data (N 5 4,760 males) from the Cohort Study on Substance Use Risk Factors (C-SURF) conducted in Switzerland were analyzed using a latent transition analysis (LTA). Symptoms of substance use (alcohol, cannabis, and tobacco) disorders and behavioral addictions (gaming and gambling) were used for identifying addiction profiles and group membership trajectories. A multinomial logistic regression model examined predictors of profile membership, while two general linear models tested whether profile membership predicted psychosocial outcomes. Results: LTA revealed three distinct profiles of symptoms of addiction, labelled Low- (91-92% of the sample), Medium- (5-7%), and High-symptom (1-3%) profiles. Thus, frequency or intensity of addiction symptoms tended to co-occur. The stability of Low-profile membership remained consistently high over time (97%), whereas the stability of Medium- and Highprofile memberships was moderate (40-49%). Sensation seeking, neuroticism, parental attitude, and poor parental monitoring were associated with Medium and High profiles compared to the Low profile. Poor relationships with parents and friends were uniquely associated with High profile, whereas hostility, sociability, and family history of mental disorders were associated withMedium profile. Education, sensation seeking, hostility, and neuroticism were associated with transitions between profiles over time. Profile membership predicted subsequent life satisfaction and negative life events. Discussion and conclusions: Symptoms of substance use disorders and behavioral addictions tend to co-occur, and profile membership is relatively stable. However, transition to less severe profiles also occurs and is influenced by education and personality traits. Our findings have implications for preventive interventions aiming at reducing the risk of addictive disorders becoming chronic and for identifying young adults most in need of support.  Kulcsszavak: addictive disorder, transition, longitudinal, development, behavioral addictions