“…The MMT group, as the mainstream therapy, also acts as a control for historic changes in the study period, such as in the availability of heroin (Baker et al, 2004;Longo, Henry-Edwards, Humeniuk, Christine, & Ali, 2004). Also of interest were potential high-risk periods: Among people entering methadone treatment, the first 14 days are considered to be of elevated risk (Caplehorn & Drummer, 1999); for those receiving naltrexone, the end of treatment is likely to increase risk (Digiusto et al, 2004).…”