Context: Despite evidence of an increase in the number of young patients receiving mental health treatment, most psychotropic medications have not been approved for the treatment of children and adolescents by the Ministry of Health, Labour and Welfare. There is little data available on psychotropic medication use in children and adolescents in Japan.
 Objective: To establish the prevalence of psychotropic medications and multiclass psychotropic polypharmacy in outpatients aged 18 years or younger in Japan between 2002 and 2010.
 Design: We used the national insurance claims database from the 2002-2010 Survey of Medical Care Activities in Public Health Insurance in Japan.
 Outcome measures: Prevalence of psychotropic prescription and psychotropic polypharmacy.
 Results: Our study dataset comprised 233,399 outpatient visits. Among patients aged 6-12 years between 2002-2004 and 2008-2010, there was a significant increase in the prevalence of ADHD medications (Odds Ratio [OR] 1.84; 95% Confidence Interval [CI] 1.33, 2.56) and antipsychotics (OR 1.58; 95%CI 1.06, 2.34), and a significant decrease in the prevalence of sedative-hypnotics (OR 0.67; 95%CI 0.46, 0.99). Among patients aged 13-18 years, there was a significant increase in the prevalence of ADHD medications (OR 2.49; 95%CI 1.34, 4.62), antipsychotics (OR 1.43; 95%CI 1.20, 1.70), and antidepressants (OR 1.37; 95%CI 1.09, 1.72). Medications that were most frequently involved used in combination of two or more psychotropic agents were mood stabilizer (93%), followed by antidepressants (77%), sedative-hypnotics (62%), antipsychotics (61%), and ADHD medications (17%).
 Conclusion: Our study revealed an increase in the use of off-label antipsychotics and antidepressants among children and adolescents. Therefore, there is an urgent need for clinical trials to evaluate the efficacy of psychotropic medications for use in children and adolescents, and the development of a clinical database to monitor the associated long-term risks and benefits.
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