In Japan, persons who committed serious crimes and are judged to have been irresponsible or to have had diminished responsibility due to mental disorders at the time of these crimes may be subjected to the Medical Treatment and Supervision Act (MTSA). The enactment of the MTSA in 2005 led to the introduction of specialized forensic mental health services. As of 2020, more than 4,000 mentally disordered offenders have received treatment under the MTSA, allowing Japan to close the gap between Western countries leading the field of forensic psychiatric treatment.
 The characteristics of the MTSA that attracted attention in the early years of its implementation include multidisciplinary team care, care meetings with community stakeholders based on the concept of the Care Programme Approach (CPA) in the United Kingdom, various psychosocial therapy programs conducted jointly by multiple professions, and the minimization of behavioral restrictions using the Comprehensive Violence Prevention and Protection Program (CVPPP). Many of these features have since been widely integrated into general, non-forensic mental health services. Since the 2010s, prescription of clozapine for treatment-resistant schizophrenia patients and use of crisis plans for social rehabilitation have been widely practiced in forensic psychiatric wards.
 An important issue related to inpatient treatment under the MTSA is the increasing average length of stay. The incidence of serious re-offenses during outpatient treatment orders under the MTSA is relatively low, although there are concerns regarding improvement of symptoms and reintegration into society, as approximately half of patients under outpatient treatment orders have been hospitalized in general psychiatric wards at least once.
 In future, psychosocial therapy targeting comorbid psychiatric disorders is expected to be developed in forensic psychiatric wards. The quality of community treatment for forensic psychiatric patients is hoped to be improved by the utilization of designated inpatient institutions. In addition, active incorporation of novel treatment approaches from general psychiatry into outpatient treatment under the MTSA may promote patients' reintegration into society.
 Authors' abstract