Tū Whakaruruhau: The evaluation of treatment outcomes for methamphetamine dependence in Aotearoa New Zealand – study protocol for a prospective longitudinal cohort study and longitudinal qualitative study

Background : Methamphetamine is the second most used illicit drug in Aotearoa New Zealand, after cannabis. Regular and heavy users of methamphetamine are likely to develop methamphetamine use disorder (MUD), and significant health and psychiatric harm. Effective treatments for MUD are limited, and relapses are common. Tū Whakaruruhau is a programme of research that aims to understand what treatment approaches are effective in managing MUD and related physical and psychological harms, in New Zealand. Methods : Tū Whakaruruhau comprises two studies. The first study is a 24-month longitudinal cohort study that will follow people receiving treatment and those not in treatment for MUD (outpatient counselling, residential treatment, and detoxification) in the Auckland, Northland, and Waikato regions of New Zealand. Data collection will occur on entry to treatment (baseline), then 3-, 12-, and 24-months later. The primary outcome is self-reported methamphetamine use (days used in the past month) at 12-months. Secondary outcomes include psychiatric comorbidity, polydrug use, change in diagnosis of MUD, criminal involvement, healthcare utilisation, and expectations and experiences of treatment. Three hundred and twenty participants (50% indigenous Māori, 240 in the Treatment Group, 80 in the Non treatment Group) will be sought for 90% power on the primary outcome. The second study is a longitudinal qualitative study involving interviews at baseline, 6-, and 12-months with 30 participants (50% Māori) from the Treatment Group, to explore their expectations of treatment and lived experiences of treatment for MUD over time. Discussion: This programme of work will provide the first evidence of treatment outcomes for MUD and the relative effectiveness of the current approaches to treating MUD, in the New Zealand context. It will provide information on what factors predict better and more equitable health outcomes. The incorporation of qualitative interviews will ensure that the participants’ treatment experiences are captured. This will inform perspectives about what treatment approaches work, and do not work, so that the most appropriate interventions are made available to support consumer needs. Findings will be incorporated into relevant reviews, informing practice and policy. Study registration Australian and New Zealand Clinical Trial Registry: ACTRN12623000438651p. Registered 1 ^st May 2023.