Methamphetamine is a highly addictive psychostimulant that adversely affects users’ physical, mental and social wellbeing (Jones et al., 2022). In the United States, overdose death rates from psychostimulants increased over 300% from 2013 to 2019, and by 2019 it was the second leading cause of overdose deaths after opioids (Lecomte et al., 2018). Among methamphetamine’s most consequential psychiatric symptoms is the development of psychosis—hallucinations, delusions, or disorganized thinking. Approximately one third of methamphetamine users develop methamphetamine-induced psychosis, which may occur without long-standing addiction or use disorder and correlates with poor outcomes and treatment engagement (Courtney & Ray, 2014). Methamphetamine psychosis is also strongly correlated with an elevated risk of mortality and healthcare utilization (Barbic, Whyte, Sidhu, Luongo, Chakraborty, et al., 2022; Barbic, Whyte, Sidhu, Luongo, Stenstrom, et al., 2022; Hajebi et al., 2018; Hjorthoj et al., 2021). Despite this growing prevalence and severity of methamphetamine use, relatively few users seek treatment (Jones et al., 2020).

To improve its treatment, methamphetamine-induced psychosis must first be identified early and appropriately. Making the diagnosis is challenging: comorbid substance use is common among patients with existing severe mental illness (Jones et al., 2020), and there is a considerable overlap of symptoms between methamphetamine psychosis and schizophrenia (Medhus et al., 2013). In addition, there is uncertainty in how to characterize psychotic symptoms occurring during periods of methamphetamine intoxication or withdrawal (Glasner-Edwards & Mooney, 2014). The diagnostic and statistical manual, Fifth Edition-Text Revision (DSM-5-TR) states that substance-induced psychosis should not be considered if symptoms persist after 1 month of intoxication or withdrawal (American Psychiatric Association, 2022). However, it is recognized that methamphetamine-induced psychotic symptoms last well beyond 1 month of abstinence (Hajebi et al., 2018). Better diagnostic guidance can facilitate clinicians’ abilities in offering evidence-based treatment for methamphetamine use disorder; educating patients and families; and avoiding iatrogenic harm of unwarranted treatments. In addition, accurate identification of methamphetamine-induced psychosis is needed to inform public health surveillance, interventions, policymaking, research and service delivery (Simpson et al., 2023).

In this study, we utilized an expert panel process to define the diagnosis of methamphetamine-induced psychotic disorder (MIPD). The a priori instructions to the panel were to produce guidance to inform diagnostic criteria and write specific criteria if possible. These proposed diagnostic criteria are intended to aid clinicians in differentiating MIPD from psychotic illnesses with similar presentations.

An expert consensus process was utilized to develop diagnostic criteria. Methods were based on best practices, applying Delphi techniques for developing clinical guidelines using electronic and remote communication (Cole et al., 2013; Colton & Hatcher, 2004; Institute of Medicine (US) Committee on Standards for Developing Trustworthy Clinical Practice Guidelines, 2011). The process and results are reported here using previously published guidance (Junger et al., 2017; Rethlefsen et al., 2021). Data were collected using RedCap, a secure web-based research collection instrument (Harris et al., 2009).

Using a consensus process, this expert panel produced novel diagnostic criteria for MIPDs. Our findings highlight some of the clinical features, progression and outcomes of methamphetamine-induced psychosis at even early stages of presentation. These criteria can guide clinicians, patients, families, scientists and policymakers who are seeking to improve the care of those with methamphetamine addiction.

This work poses important issues for the clinical management of methamphetamine psychosis. The panel repeatedly raised the importance of considering symptom timing in the treatment of MIPD. Panellists agreed that psychotic symptoms of methamphetamine use merit recognition whether they occur during intoxication, withdrawal or thereafter. These symptoms may vary somewhat over the course of recovery: acute MIPD is characterized by specific hallucinations and delusions, whereas the psychotic content seen in chronic PMIPD cannot be differentiated from primary psychosis. The patient’s prior history of use and symptom onset are important for the diagnosis of both AMIPD and PMIPD, albeit more so for PMIPD. In addition, it is important for providers to recognize other physical, psychological and behavioural symptoms of methamphetamine intoxication beyond psychosis, as these could be crucial clues that the patient is experiencing AMIPD. These conclusions can be considered a clinically expert interpretation of prior scientific literature and topic reviews that have posed a range of nuanced and conflicting reports on the nature of methamphetamine psychosis.

These criteria are an important step in advancing the science of methamphetamine addiction. Panellists’ backgrounds reflected a variety of practice settings, regions, and personal and professional backgrounds; several members reported having lived experience with addiction. Nevertheless, future work can improve the validity and usefulness of these criteria. This work may include tests of interrater reliability between providers; review of criteria by larger groups of clinicians or persons with lived experience; and study of the criteria’s use in clinical practice. Notwithstanding the importance of these next steps, the panel more strongly felt that other research topics were of greater importance: understanding risk factors for progression from acute to persisting MIPD or examining medication treatments for MIPD. These highly experienced panellists likely felt urgency to advance the science of addiction treatment for their patients. These results also suggest the importance of early identification and management in clinical care.

Our methodology likely contributed to the high consensus achieved for the final diagnostic criteria. Iterative web-based survey voting began with open-ended themes and was increasingly targeted towards the specific form and content of potential final criteria. Panel surveys were complemented by email and conference discussion. Participants had access to scientific literature and assistance for problem-solving technical barriers to participation. The specific content of the final criteria reflects terminology, symptoms and timeframes that attained high rates of endorsement through preceding surveys. The high response rates and positive experiences reported by panellists obviate the risk of participation bias.

There are limitations to these findings. Given the highly specific task of the panel in developing diagnostic criteria related to psychiatric and psychotic symptoms, we recruited psychiatrists likely to work closely with patients who have methamphetamine psychosis, including in emergency and crisis settings. The strict criteria for panel inclusion may have promoted homogeneity of panellists’ experience and led to a higher likelihood of developing consensus; an intentionally high bar of ≥80% was thus set for endorsing criteria. This work only included English-speaking clinicians and English literature notwithstanding a long history of methamphetamine addiction science occurring in other countries, notably in Asia. Results of the literature search were not judged or curated for quality, as our intent was to provide a range of references with minimal risk of biassing participants. A large electronic library was available for participants, but we did not review the full text of all articles prior to making them available to panellists. Moreover, panellists likely have variable expertise in reviewing and interpreting scientific literature, and we did not examine individual panellists’ reasoning behind their opinions or literature assessments. These criteria reflect an important expert consensus on this topic, but ongoing study of their use in practice and correlation with patient outcomes will be needed.

Methamphetamine-induced psychotic disorder is a highly prevalent, dangerous and complex disorder that is difficult to identify and treat. This panel poses specific diagnostic criteria for acute MIPD and persisting MIPD that will inform patient care and support researchers in studying this disease. Many clinicians and staff struggle to treat persons with difficult symptoms of methamphetamine addiction; these criteria can help providers understand and manage the most severe manifestations of patients’ methamphetamine use. Ultimately, these criteria represent a necessary initial step in improving the care of millions worldwide with methamphetamine addiction.

SUPPORTING INFORMATION

Additional supporting information can be found online in the Supporting Information section at the end of this article.