Clinical characteristics and treatment resource utilization among patients with substance use disorders: A comparative study of individuals who misuse pharmaceuticals and use illegal drugs.

Aim: In Japan, drug-related issues are diverse, and the use of cannabis and pharmaceuticals is rising. This study aimed to clarify the differences in clinical characteristics and treatment resource utilization by drug type. Methods: We analyzed data from 891 individuals from the 2024 Nationwide Psychiatric Hospital Survey, which comprised 368 who used methamphetamine or cannabis (illegal drug group) and 523 who used hypnotics, anti-anxiety, or over-the-counter medications (pharmaceutical group). Clinical characteristics and use of treatment resources were compared by estimating risk differences and conducting logistic regression analyses. Results: The pharmaceutical group had more young women, individuals who engaged in self-harm, and those with comorbid psychiatric disorders than the illegal drug group. The illegal drug group had more males and individuals aged 30 years or older, with many meeting criteria for dependence syndrome. Moreover, they showed significantly higher use of outpatient group therapy, self-help groups, and rehabilitation facilities. In the logistic regression analysis, the pharmaceutical group was independently associated with female sex, self-harm, and comorbid psychiatric disorders, and were less likely to use outpatient group therapy but more likely to have a history of psychiatric hospitalization. Conclusion: Illegal drug users more frequently accessed addiction-specific services, whereas pharmaceutical users were more likely to receive psychiatric interventions. This suggests that pharmaceutical users have difficulty accessing traditional rehabilitation resources. Therefore, there is a need for a more comprehensive system that collaborates with general psychiatric care and offers flexible and tailored support.