Predictors of Marijuana Relapse in the Human Laboratory: Robust Impact of Tobacco Cigarette Smoking Status

BACKGROUND Few marijuana smokers in treatment achieve sustained abstinence, yet factors contributing to high relapse rates are unknown. METHODS Study 1: data from five inpatient laboratory studies assessing marijuana intoxication, withdrawal, and relapse were combined to assess factors predicting the likelihood and severity of relapse. Daily, nontreatment-seeking marijuana smokers (n = 51; 10 ± 5 marijuana cigarettes/day) were enrolled. Study 2: to isolate the effects of cigarette smoking, marijuana intoxication, withdrawal, and relapse were assessed in daily marijuana and cigarette smokers (n = 15) under two within-subject, counter-balanced conditions: while smoking tobacco cigarettes as usual (SAU), and after at least 5 days without cigarettes (Quit). RESULTS Study 1: 49% of participants relapsed the first day active marijuana became available. Tobacco cigarette smokers (75%), who were not abstaining from cigarettes, were far more likely to relapse than non-cigarette smokers (odds ratio: 19, p < .01). Individuals experiencing more positive subjective effects (i.e., feeling "high") after marijuana administration and those with more negative affect and sleep disruption during marijuana withdrawal were more likely to have severe relapse episodes (p < .05). Study 2: most participants (>87%) relapsed to marijuana whether in the SAU or Quit phase. Tobacco cigarette smoking did not significantly influence relapse, nor did it affect marijuana intoxication or most symptoms of withdrawal relative to tobacco cessation. CONCLUSIONS Daily marijuana smokers who also smoke cigarettes have high rates of marijuana relapse, and cigarette smoking versus recent abstinence does not directly influence this association. These data indicate that current cigarette smoking is a clinically important marker for increased risk of marijuana relapse.