Relationships between local school closures due to the COVID-19 and mental health problems of children, adolescents, and parents in Japan

•We investigated local school closures and child and parent mental health in Japan.•Our sample comprises Japanese parents who filled in an online nationwide survey.•School closures were associated with increased child and parent mental health.•Support to mitigate the potential mental health impacts on families is needed. The widespread impacts of COVID-19 have affected both child and parent mental health worldwide. This study aimed to investigate the relationship between school closures due to COVID-19 and child and parent mental health in Japan. A sample of 1,984 Japanese parents with children and adolescents aged 6–15 years participated. The parents responded to online questionnaires about their own mental health and that of their children cross-sectionally. Participants were divided into three school situations based on the past week: full school closure, partial school closure, and full school open. Results indicated that 2.02% (n = 40) of the participants were in full school closure and 5.95% (n = 118) of the participants were in partial school closure. The results indicated that, after controlling for other variables regarding the pandemic, full school closure was associated with much higher scores in both child and parent mental health problems compared to full school open. Moderately higher scores were found only for anxiety symptoms in both children and parents under partial school closure compared to where schools were fully open. Consideration of the needs of families is necessary in the context of both full and partial school closures to prevent deteriorating mental health.