ObjectivesTo clarify the dissemination status of cognitive behavioural therapy (CBT) in Japan under the national health insurance scheme.DesignRetrospective observational study.SettingNational Database of Health Insurance Claims and Specific Health Checkups of Japan.ParticipantsPatients who received CBT under the national health insurance scheme from fiscal years (FY) 2010 to 2015.Primary and secondary outcome measuresWe estimated the change rate and the standardised claim ratio (SCR) for the number of patients receiving CBT and analysed the association between the CBT status and several regional factors.ResultsWe found that (a) a total of 60 304 patients received CBT during the study period; (b) the number of patients receiving CBT was highest in the first year (−1.8% from FY2010 to FY2015); (c) the number of patients who received CBT per 100 000 population decreased (or remained at zero) in most prefectures (32 out of 47); (d) there was a maximum 424.7-fold difference between prefectures in the standardised claim ratio for CBT and (e) the number of registered CBT institutions was significantly associated with the number of patients who received CBT.ConclusionsThe provision of CBT did not increase in the first 6 years (FY2010–2015) after its coverage in Japan’s national health insurance scheme. Further studies including a questionnaire survey of registered CBT institutions are required to get more detailed information on the dissemination of CBT in Japan.

The use of computed tomography (CT) scanning has increased worldwide over the decades, and Japan is one of the leading countries in annual frequency of diagnostic CT. Although benefits of CT scan are undisputable, concerns have been raised about potential health effects of ionizing radiation exposure from CT, particularly among children who are likely more susceptible to radiation than adults. Our study aims to evaluate the cumulated lifetime risk of the brain/central nervous system (CNS) cancer due to head CT examinations performed on Japanese children at age 0 to 10 years in 2012, 2015 and 2018. The frequency and dose distribution of head CT examinations were estimated based on information from recent national statistics and nationwide surveys. The lifetime risk attributable to exposure was calculated by applying risk models based on the study of Japanese atomic‐bomb survivors. In contrast to the overall increasing trend, the frequency of childhood CT, especially at age < 5, was decreasing, reflecting a growing awareness for efforts to reduce childhood CT exposure over the past decade. In 2018, 138 532 head CT examinations were performed at age 0 to 10, which would consequently induce a lifetime excess of 22 cases (1 per 6300 scans) of brain/CNS cancers, accounting for 5% of the total cases. More excess cases were estimated among men than among women, and excess cases could emerge at relatively young ages. These results would have useful implications as scientific basis for future large‐scale epidemiological studies and also as quantitative evidence to justify the benefits of CT vs risks in Japan.