Methamphetamine in Japan: the consequences of methamphetamine abuse as a function of route of administration.

AIMS: To determine differences in life backgrounds and clinical features between methamphetamine (MAP) smokers and injectors in Japan. SETTING: Out-patient clinic at a psychiatric centre. PARTICIPANTS: Among 451 MAP abusers undergoing initial assessments, 116 subjects whom the first author had directly interviewed and treated were studied. DESIGN AND PROCEDURES: In this study, life backgrounds, clinical features and psychiatric symptoms were compared between three subgroups: 42 (36.2%) in group S (smoking only); 57 (49.1%) in group I (injection only); and 17 (14.7%) in group SI (initially smoking, later injecting). FINDINGS: Group I more often had parental absence (P < 0.001), a family history of alcoholism (P < 0.05), limited education (P < 0.001), or a criminal record (P < 0.001) than patients in the other two groups. Group S had the most cannabis use (P < 0.01), while group I had the most volatile solvents use (P < 0.01). Group S experienced their first psychotic episode sooner after first MAP use (P < 0.01), but showed fewer auditory hallucinations at initial assessment than patients in other groups (P < 0.001). Group SI was intermediate between groups S and I in life background, clinical features and psychotic symptoms, while they had lost control of their drug use most frequently (P < 0.02). CONCLUSIONS: In Japan, MAP smokers have different life backgrounds from injectors. Smoking MAP does not appear to be a safer route as regards losing control of MAP use and inducing psychosis than injection.