Retention in treatment is often highlighted as one of the key indicators of success in opioid maintenance treatment (OMT) (Ball and Ross, 1991, Bell et al., 2006, Judson et al., 2010 and Zhang et al., 2003), emphasising the fact that adequate long-term adherence to treatment services, both medical and psychosocial, is essential for therapeutic benefits to accrue.
Treatment compliance for drug dependence is generally poor, and although retention rates are normally higher in maintenance treatment than in other forms of substance abuse treatment, patients differ in the nature and duration of their engagement with treatment (Bell et al., 2006). Premature discontinuation of OMT presents major challenges to successful treatment outcomes and unexpected dropouts are associated with a number of risk behaviours. Studies have shown that newly discharged methadone patients often relapse into more drug use (Gossop, Green, Philips, & Bradley, 1989) and are at a high risk of overdose mortality (Degenhardt et al., 2009 and Dolan et al., 2005) in the period following treatment dropout.
Research on factors that are associated with treatment dropout is essential. Earlier studies have investigated determinants of retention in OMT and concluded that both pre-treatment factors such as being male (Kelly, O'Grady, Mitchell, Brown, & Schwartz, 2011), being younger (Burns et al., 2009, Mancino et al., 2010 and McHugh et al., 2013) and being involved with the criminal justice system (Kelly et al., 2011 and Magura et al., 1998), and in-treatment factors such as receiving lower doses of methadone (Caplehorn et al., 1994, Mohamad et al., 2010, Peles et al., 2006 and Sarasvita et al., 2012), continued illicit drug use (Davstad et al., 2007 and Peles et al., 2006) and alcohol use (Stenbacka, Beck, Leifman, Romelsjo, & Helander, 2007) have been associated with treatment dropout. However, with some exceptions (Burns et al., 2009 and Davstad et al., 2007), this research is often hampered by being based on selective groups of patients (Kelly et al., 2011, Magura et al., 1998, Mancino et al., 2010 and McHugh et al., 2013) and having inadequate follow-up time (Mohamad et al., 2010 and Sarasvita et al., 2012).
Few earlier studies have investigated treatment retention in a complete national cohort of patients with no patients lost to follow-up over a longer period. Against this background, the main objective of this study was to investigate long-term participation in opioid maintenance treatment, with an 18 month follow-up, in a national cohort of patients. Further aims were to analyse factors associated with retention in treatment and factors associated with re-entry to OMT and to describe patterns of participation in subsequent treatment episodes.
