Secondary outcomes included days to relapse following the TQD (using Cox proportional hazards modeling) and withdrawal symptoms. For the time to relapse analysis, self-reported abstinence for the past 7 days at weekly intervals up to 6-month follow-up was used. We assessed withdrawal symptoms on the TQD using a self-report checklist assessing the severity (in the past 7 days) of common symptoms, including irritability, difficulty in concentrating, anxiousness, insomnia, drowsiness, nausea and general physical complaints (e.g. sweating, dizziness). Responses to each item was scored from 0= not at all to 3 = severe and were summed to create a withdrawal severity index (total scores could range from 18 to 60).
