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

Abstract This study evaluated the explanatory power of the theory of planned behavior (TPB) and examined past behavior and habit strength as non-conscious predictors of cannabis use frequency. It also explored whether the model’s explanatory power was consistent across gender and college status. Using non-probability targeted sampling, we recruited 606 Spanish-speaking young adults (aged 18–25, M = 21.04, SD = 2.15; 61.2% male) who reported cannabis use in the past month from public venues. Participants completed an initial survey assessing cannabis use frequency, TPB constructs, and habit strength. Three months later, 501 (82.6%) completed a follow-up assessment of cannabis use frequency and habit strength. The TPB model accounted for 39.2% of the variance in cannabis use intention and 56.2% of the variance in cannabis use frequency. The extended model, which included past behavior and habit strength (at both time points), accounted for 65.7% and 67.6%, respectively. Baseline habit strength was not significantly associated with intention. Past behavior and habit strength at follow-up showed the strongest associations with cannabis use frequency, while associations involving deliberative constructs were attenuated. 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.