Japanese Cannabis Patients Are Younger and Less Severe Than Methamphetamine Patients but Underserved by Support | Research

The takeaway

Compared to methamphetamine patients, those with cannabis-related mental disorders in Japan were younger, had fewer criminal records and psychiatric comorbidities, but were less likely to access self-help groups or recovery services.

Addiction treatment planners and policymakers in Japan and countries with emerging cannabis treatment needs.

Cannabis patients younger and less severe but underserved by support resources

What the researchers found

Cannabis patients (n=82) were younger than methamphetamine patients (n=208), had fewer drug-related criminal offences, less incarceration history, fewer comorbid psychiatric disorders, and less severe substance use disorder. However, they had less experience with self-help groups or recovery support facilities. Use of nonmedical resources was more strongly associated with older age and disorder severity than with substance type.

Why it matters

Japan is seeing increasing numbers of young cannabis-related arrests and treatment-seekers. Current recovery support resources may be designed around the profile of older, more severe methamphetamine users and may not meet the needs of this younger, less severe cannabis population.

The numbers in context

N = 290 (208 methamphetamine, 82 cannabis), all male. Cannabis group: younger, fewer criminal offences, fewer comorbid psychiatric disorders, less severe SUD, less use of self-help groups and recovery facilities.

How the study worked

Data from the 2024 Nationwide Survey on Drug-Related Mental Disorders in Japanese Psychiatric Hospitals. Compared 208 male methamphetamine cases and 82 male cannabis cases on clinical variables. Logistic regression examined factors associated with use of self-help groups and recovery support.

What this study cannot tell us

Male patients only from psychiatric hospital settings. Japan's strict drug policy context limits generalizability. Cross-sectional design cannot determine trajectories. Cannabis group is relatively small (n=82).

How to read the evidence

National survey from Japanese psychiatric hospitals. Moderate evidence limited by all-male sample and cross-sectional design.

When this study was published

Published in 2025 using 2024 survey data.

The bigger picture

As Japan considers cannabis policy reform, understanding the clinical profile of cannabis patients relative to other drug users is essential for designing appropriate treatment services. The current system appears oriented toward older, more severe users.

Questions still open

Should Japan develop cannabis-specific treatment programs for younger users? Would lowering barriers to recovery support increase engagement among cannabis patients?

Common questions

Why compare cannabis and methamphetamine patients?

Methamphetamine has historically been the dominant drug of concern in Japan. As cannabis cases rise, understanding how these populations differ helps design appropriate treatment services.

Why are cannabis patients less connected to support?

Age and severity drove support utilization more than substance type. Cannabis patients were younger and less severe, making them less likely to engage with existing resources designed for older, more impaired populations.

Read the original research

Clinical Characteristics of Patients With Cannabis-Related Mental Disorders and an Examination of Factors Influencing Their Access to Medical and Nonmedical Resources: Comparison of Methamphetamine-Related Mental Disorders.

Neuropsychopharmacology reports, 45(3), e70051

View on PubMed ↗Publisher’s paper ↗

Citation

Matsumoto, Toshihiko; Usami, Takashi; Nishimura, Akiho; Higuchi, Sayako; Okita, Kyoji; Shimane, Takuya. (2025). Clinical Characteristics of Patients With Cannabis-Related Mental Disorders and an Examination of Factors Influencing Their Access to Medical and Nonmedical Resources: Comparison of Methamphetamine-Related Mental Disorders.. Neuropsychopharmacology reports, 45(3), e70051. https://doi.org/10.1002/npr2.70051