Lay summary
Methamphetamine (MA) is the second most commonly used illicit drug in Aotearoa New Zealand (NZ). Regular/heavy users are likely to develop a dependence syndrome and experience a range of physical and psychological adverse effects; many will return to using following attempts at abstinence. Given these adverse effects, some people who use MA are likely to want or need to access treatment to help them reduce the harms associated with their use, and to ultimately quit. However, the availability of effective treatment options, and the evidence about what works for problematic MA use, is limited. The aim of this research is to improve our understanding of what treatment approaches reduce MA use and related physical and psychosocial harms, and to identify the predictors of positive treatment outcomes in NZ.