Twelve studies (n=9,718) met the inclusion criteria. The designs of these studies were not clear, although the authors reported that studies were mostly naturalistic follow-up studies. Two of the studies appeared to be randomised controlled trials. The duration of follow-up ranged from 1 month to 103.2 months.
Overall, 33% of patients in the included studies were abstinent (or had a period of abstinence) from at least opioids for an average of 2 years following detoxification. The rates of abstinence ranged from 22 to 86%.
Treatment characteristics. The abstinence rates were higher in patients who volunteered to participate in detoxification programmes compared with those whose participation was based on staff recommendation (47% versus 23%). Methadone maintenance dose and psychosocial support were not related to abstinence rate.
Inconsistencies were reported in the relationship between patient characteristics and abstinence rates. Age, ethnicity and educational level were all shown to have a positive relationship with abstinence rate in some studies, but not others. Similarly, duration or severity of dependence, detoxification difficulties, social problems and criminal behaviour were shown to have a negative relationship in some studies, but not others.