Aims: To examine whether personality traits predict the course of addictive behaviours in general and whether predictive associations differ between non-substance related (NR) and substance related (SR) addictive behaviours. Methodology: We recruited 338 individuals (19-27 y, 59 % female) from a random community sample with NR, SR, or no DSM-5 addictive disorder. Predictors were the Big Five personality traits (NEO-FFI) and reward and punishment sensitivity (BIS/BAS questionnaire). Outcomes were the slopes of addictive behaviours (i. e., quantity, frequency, and number of DSM-5 criteria) over three years. Bayesian multiple regressions were used to analyse the probabilities for each hy-pothesis. Results: The evidence that higher neuroticism, lower conscientiousness, lower agreeableness, higher extraversion, lower openness, higher reward sensitivity, and lower punishment sensitivity predict increased addictive behaviours over time was, overall, moderate to high (69 % to 99 %) and varied by trait and outcome. Predictive associations were mostly higher for NR compared with SR addictive behaviours. Con-clusions: Personality traits predict the course of addictive behaviours, but associations were only about half as large as expected. While some personality traits, such as lower conscientiousness, predict increases in both NR and SR addictive behaviours over time, others, such as lower punishment sensitivity, seem to specifically predict increases in NR addictive behaviours.