Baseline trajectories of heavy drinking and their effects on postrandomization drinking in the COMBINE Study: empirically derived predictors of drinking outcomes during treatment.
The Combined Pharmacotherapies and Behavioral Interventions (COMBINE) Study sought to answer questions about the benefits of combining behavioral and pharmacological interventions (naltrexone and acamprosate) in alcohol-dependent patients. Our goals were to identify trajectories of heavy drinking before randomization in COMBINE, to characterize patients in these trajectories, and to assess whether prerandomization trajectories predict drinking outcomes. We analyzed daily indicators of heavy drinking 90 days before randomization using a trajectory-based approach. Each patient was assigned to the most likely prerandomization heavy-drinking trajectory, and the baseline characteristics of participants in the baseline trajectories were compared. The main and interactive effects of these trajectories and treatment factors (acamprosate, naltrexone, or combined behavioral intervention) on summary drinking measures during active treatment (16 weeks) were assessed. We identified five trajectories of heavy drinking prerandomization: "T1: frequent heavy drinkers"; "T2: very frequent heavy drinkers"; "T3: nearly daily heavy drinkers"; "T4: daily heavy drinkers"; and "T5: daily heavy drinkers stopping early" before randomization. Trajectory membership was significantly associated with all drinking outcomes. Patients in "T5: daily heavy drinkers stopping early" had comparable drinking outcomes to those in "T1: frequent heavy drinkers," whereas the remaining trajectories were associated with significantly worse outcomes. The baseline trajectory did not interact significantly with the treatment condition. These exploratory analyses confirmed the hypothesis that baseline trajectories predict postrandomization drinking outcomes. Interestingly, "T5: daily heavy drinkers stopping early" had outcomes that were comparable to the least severe baseline trajectory "T1: frequent heavy drinkers," and baseline trajectories of heavy drinking did not moderate the treatment effects.