When habits are dangerous - Alcohol expectancies and habitual decision-making predict relapse in alcohol dependence

Abstract Background Addiction is supposed to be characterized by a shift from goal-directed to habitual decision-making, thus facilitating automatic drug intake. The two-step task allows distinguishing between these mechanisms by computationally modelling goal-directed and habitual behavior as model-based and model-free control. In addicted patients, decision-making may also strongly depend upon drug-associated expectations. Therefore, we investigated model-based vs. model-free decision-making and its neural correlates as well as alcohol expectancies in alcohol-dependent patients and healthy controls and assessed treatment outcome in patients. Methods Ninety detoxified, medication-free alcohol-dependent patients and 96 age- and gender- matched controls participants underwent functional magnetic resonance imaging during the two-step task. Alcohol expectancies were measured with the Alcohol Expectancy Questionnaire. Over a follow-up period of 48 weeks, 37 patients remained abstinent whereas 53 patients relapsed as indicated by the Timeline Follow-back method. Results Patients who relapsed displayed reduced medial prefrontal cortex (mPFC) activation during model-based decision-making. Furthermore, high alcohol expectancies were associated with low model-based control in relapsers, while the opposite was observed in abstainers and healthy controls. However, reduced model-based control per se was not associated with subsequent relapse. Conclusions These findings suggest that poor treatment outcome in alcohol dependence does not simply result from a shift from model-based to model-free control but is rather dependent on the interaction between high drug expectancies and low model-based decision-making. Reduced model-based mPFC signatures in relapsers point to a neural correlate of relapse risk. These observations suggest that therapeutic interventions should target subjective alcohol expectancies.