Consultation-liaison psychiatry in Japan: a nationwide retrospective observational study

BACKGROUND: Consultation-liaison psychiatry (CLP)—professional psychiatric care provided to coordinate with surgical or medical treatment of inpatients with psychiatric disorders—was included in universal health coverage in Japan in 2012. Despite evidence of benefits of CLP, basic data and geographic distribution information regarding CLP at the national level remain unclear. This study aimed to 1) identify the geographic disparity of CLP in Japan and 2) investigate the association between number of consultations per CLP patient and region. METHODS: We retrospectively analyzed anonymized data retrieved from the Japanese administrative inpatient database regarding inpatients who were provided CLP between April 2012 and March 2017. Demographic characteristics were summarized and geographic disparity by prefecture was visualized for fiscal years 2012 and 2016; we also summarized the data according to region. Multivariate linear regression analysis was used to investigate association between the number of consultations per CLP patient and region after adjusting for covariates. RESULTS: Data from a total of 46,171 patients who received 138,866 CLP services were included. Results revealed more patients aged 75–84 years received CLPs than any other age group (29.7%) and the overall male/female ratio was 53:47 in 2016. In 2012 and 2016, 24.2 and 30.7% of CLP patients, respectively, were transferred to other hospitals; 9.7 and 8.8%, respectively, discharged due to the death. CLP services were provided in 14 prefectures in 2012 and 33 by 2016; 14 prefectures had no available CLP services. After adjusting for covariates, Tohoku (β = − 0.220, p < 0.034), Chugoku (β = − 0.160, p < 0.026), and Shikoku (β = − 0.555, p < 0.001) had a significant negative correlation with the number of consultations per CLP patient compared with Hokkaido region (an adjusted R square (R2) = 0.274). CONCLUSIONS: Our study clarified the characteristics of patients in Japan who received CLPs and the geographic disparity in CLP services. Although 5 years had passed since CLP was introduced, the results imply wide availability of CLP nationally. The analysis data provided may inform future policies to improve CLP services. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12888-021-03241-y.