The Role of Habit and Past Behavior in Cannabis Use: An Extended Theory of Planned Behavior Model

This study evaluated the explanatory power of the Theory of Planned Behavior (TPB), and examined the role of past behavior and habit strength as non-conscious processes in predicting cannabis use frequency. It also explored whether the model’s explanatory power was consistent across gender and college status. A targeted sample of 501 young adults (aged 18-25, M = 20.99, SD = 2.12; 60.7% male) who reported cannabis use completed an initial survey assessing cannabis use frequency, TPB constructs, and habit strength. Three months later, a follow-up survey assessed cannabis use frequency and habit strength. The TPB model demonstrated strong predictive utility, explaining 42.8% of the variance in cannabis use intention and 55.4% in actual behavior. Adding habit strength and past behavior enhanced the model’s predictive validity, increasing the explained variance to 66.1% for intention and 67.7% for behavior. Past behavior and habit strength emerged as the strongest predictors of cannabis use frequency, attenuating the effect of deliberative constructs. The extended TPB model was invariant across gender and college status. While the TPB offers a solid framework for understanding cannabis use behavior, these findings highlight the need to consider both non-conscious and deliberative processes when designing interventions aimed at reducing cannabis use.