Social cognitive predictors of treatment outcome in cannabis dependence.

BACKGROUND: Drug-related outcomes expectancies and refusal self-efficacy are core components of Social Cognitive Theory. Both predict treatment outcome in alcohol use disorders. Few studies have reported expectancies and refusal self-efficacy in cannabis dependence. None have examined both, although both constructs are key targets in Cognitive-Behavioural Therapy (CBT). This study tests the predictive role of expectancies and refusal self-efficacy in treatment outcome for cannabis dependence.

DESIGN: Outpatients completed a comprehensive assessment when commencing cannabis treatment and predictors of treatment outcome were tested.

SETTING: A university hospital alcohol and drug outpatient clinic.

PARTICIPANTS: 221 cannabis-dependent patients participated in a 6-week CBT program where the goal was abstinence.

MEASUREMENTS: Cannabis Expectancy Questionnaire and Cannabis Refusal Self-Efficacy Questionnaire, cannabis dependence severity [Severity of Dependence Scale], psychological distress [General Health Questionnaire] at baseline; the timeline follow-back procedure at baseline and each session.

FINDINGS: Patients reporting lower confidence in their ability to resist cannabis during high negative affect (emotional relief refusal self-efficacy) had a lower likelihood of abstinence (p=0.004), more days of use (p<0.001), and larger amount used (p<0.001). Negative cannabis expectancies predicted greater likelihood of abstinence (p=0.024). Higher positive expectancies were associated with lower emotional relief self-efficacy, mediating its association with outcome (p<0.001).

CONCLUSIONS: Emotional relief refusal self-efficacy and negative expectancies are predictive of better treatment outcomes for cannabis dependence. Positive expectancies may indirectly predict poorer outcome because of a negative association with self-efficacy, but this conclusion remains tentative as directionality could not be established.