Introduction: Methamphetamines are highly addictive central nervous system stimulants and are associated with many physical health complications. It is critical to understand co-occurring mental disorders among those who use meth for evidence-informed prevention and treatment services. Assessing the prevalence of pre-existing mental disorders and subsequent risk for incident diagnosis of mental disorders is challenging without access to whole-population health data.

Objectives and Approach: We hypothesized that people with methamphetamine use had increased risk for a pre-existing mental disorder and increased risk for an incident diagnosis of a mental disorder, when compared with a matched cohort after adjusting for measured confounders. We used whole-population data from the single-payer healthcare system in Canada to capture all contacts with paramedics, the emergency department, all hospital discharges, medical claims, and diagnostic labs where methamphetamine use was documented in Winnipeg, Manitoba Canada (2013-2018). We looked back five years before their first methamphetamine-related contact and forward one year to identify mental disorders: mood and anxiety, substance use (other than methamphetamine use), psychotic disorders, and personality disorders. We used a 5-year washout to determine incident disorders. We tested for differences in prevalence and incidence of mental disorders using generalized linear models.

Results: 3,665 individuals living in Winnipeg, had a methamphetamine-related healthcare contact. Those who consumed methamphetamine had 3.3 times the risk for pre-existing diagnosed mood and anxiety disorder and diagnosed psychotic disorders (aRR 13.7). Those who had used methamphetamine had 2.1 times the risk of having an incident diagnosis for mood and anxiety disorder during the year following their first methamphetamine-related healthcare contact and 43.7 times the risk of receiving an incident psychotic disorder diagnosis.

Conclusion: People presenting to the healthcare system having used methamphetamines do so with complex needs, including mental disorder comorbidities. Prevention and treatment strategies need to consider these and other determinants of health.