Loneliness increased over 40 years in Japan
Researchers found a rise in loneliness from 1983 to 2023 using a cross-temporal meta-analysis
Chuo University
image:
Trends in loneliness in Japanese society from 1983 to 2023. The horizontal axis represents the investigation year of study, and the vertical axis represents mean of the UCLA Loneliness Scale scores. Each dot corresponds to an individual data point. As shown by the trend line, loneliness in Japan increased over the 40 years.
view moreCredit: Momo Homma, Master's Student, Graduate School of Letters, Chuo University Kenkichi Takase, Professor, Department of Psychology, Faculty of Letters, Chuo University
Despite widespread claims that social changes have intensified loneliness, no study has yet examined how loneliness has changed over time in Japan. To address this gap, graduate student Momo Homma from the Department of Psychology at Chuo University, Japan and Professor Kenkichi Takase from the same institution conducted a cross-temporal meta-analysis to investigate how loneliness has changed over time in Japan and identify the factors contributing to this change. The results indicated that loneliness increased in Japan from 1983 to 2023. Furthermore, the increase was particularly pronounced among adolescents and women, and social indicators such as marriage rates were found to covary with loneliness. These findings provide a foundation for future research on loneliness and help identify target populations for interventions aimed at reducing loneliness.
Previous research has linked loneliness to mental and physical health, as well as to health-related behaviors, and has also shown that it is associated with increased mortality risk. The World Health Organization has identified loneliness as “a global public health concern” and has positioned it as a public health priority. In Japan, loneliness is also emerging as a social issue. However, its long-term trends have not been systematically examined. Therefore, in this study, we used a cross-temporal meta-analysis to investigate how loneliness has changed over time in Japan.
In this study, we searched four databases (PubMed, Web of Science, J-STAGE, and CiNii) to identify studies conducted in Japan that used the UCLA Loneliness Scale. In the English-language databases, we used the search terms “UCLA Loneliness Scale, Japan” and “UCLA Loneliness Scale, Japanese.” In the Japanese databases, we searched for “UCLA Loneliness Scale (in Japanese).” We also included additional studies identified through the review process. The search yielded 333 records. After removing duplicates and screening abstracts, 251 studies remained. We then applied the exclusion criteria and conducted a full-text review, resulting in a final sample of 81 studies comprising 183 datasets (N = 49,054) included in the meta-analysis. Subsequently, we performed data coding and score adjustments.
The main analysis revealed a significant increase in UCLA Loneliness Scale scores from 1983 to 2023. This finding suggests that loneliness in Japan may have worsened over the past 40 years. Secondary analyses also revealed effects of developmental stage and gender. Regarding developmental stage, loneliness increased among adolescents. In terms of gender, although men consistently showed higher levels of loneliness, an increasing trend was observed only among women. Further analyses also revealed the influence of social indicators. When loneliness scores were compared before and during the COVID-19 pandemic, loneliness score was higher during the pandemic. In addition, the increase in loneliness covaried with social indicators such as the number of single-person households, marriage rates, GDP, and Internet use.
This study is the first to investigate how loneliness has changed over time in Japan. The results show a substantial increase in loneliness and factors contribute to this trend. The findings highlight loneliness as a pressing social issue and provide key evidence supporting the need for further scientific research and policy interventions.
Increases in loneliness were particularly evident among adolescents and women, highlighting the need for targeted support. To address loneliness in adolescence, future work will explore whether dietary interventions can help reduce loneliness. If effective, we will further examine the underlying biological mechanisms, including the gut–brain axis. To support women, particularly mothers, we are developing a generative AI–based support system (an “AI childcare worker”) designed to alleviate loneliness. We will evaluate its effectiveness and work toward its real-world implementation.
【Glossary】
1) Loneliness
Loneliness is defined as a subjective negative emotional state resulting from a perceived discrepancy between desired and actual interpersonal relationships. It is distinguished from social isolation, which denotes an objective lack of social connections.
2) Cross-temporal meta-analysis
A method of meta-analysis that uses mean scores of psychological measures to examine changes in those measures over time. Meta-analysis integrates findings from multiple studies to draw overall conclusions and is considered a high level of evidence.
Journal
Frontiers in Psychology
Method of Research
Meta-analysis
Subject of Research
Not applicable
Article Title
Increasing loneliness in Japan, 1983–2023: a cross-temporal meta-analysis
New research finds low-dose buprenorphine may help sustain ketamine’s benefits for suicidal ideation
San Francisco, California, May 18, 2026 — New research published online today in the American Journal of Psychiatry finds that low-dose buprenorphine, given after a single ketamine infusion, significantly sustained reductions in suicidal ideation in adults with major depressive disorder. The randomized, double-blind, placebo-controlled trial is the first to show that a pharmacologic intervention may help maintain and build on ketamine’s anti-suicidal effects in this at-risk population.
Ketamine is known to reduce suicidal thoughts very quickly, often within hours; however, its benefits usually do not last long. In the study, 50 adults with major depression and clinically significant suicidal ideation received a single open-label intravenous infusion of ketamine. Two days later, participants were randomly assigned to receive either low-dose buprenorphine or a placebo for four weeks. Forty-five participants completed at least one week of follow-on treatment and were included in the primary analysis. Both groups improved, but the buprenorphine group showed significantly greater reductions in suicidal ideation over time than the placebo group. At week four, there was a 76% reduction in suicidal ideation in the ketamine and buprenorphine group, compared to a 43% reduction in the ketamine and placebo group.
Depression scores improved in both groups during the study, but differences between groups were not statistically significant. No serious treatment-related adverse events occurred.
Two of the study’s authors presented their findings at the Annual Meeting of the American Psychiatric Association. The findings are notable because there are currently no FDA-approved medications specifically indicated to reduce suicidal ideation in major depressive disorder. The authors conclude that the ketamine-buprenorphine sequence may represent a potentially scalable and safe therapeutic option for patients at risk of suicide.
"This is the second trial to indicate that buprenorphine at low doses reduces suicidal ideation in major depression,” said Allen Schatzberg, M.D., senior author on the study. “However, unlike earlier reports, the degree of reduction was enhanced markedly by pretreating with intravenous ketamine. The similarities of the buprenorphine findings and the availability of both drugs for clinical use could rapidly increase the potential adoption of the sequence as a treatment strategy to reduce suicidality.”
Christine Yu Moutier, M.D., chief medical officer of the American Foundation for Suicide Prevention (AFSP), which was one of the study's funders, was also at the presentation to underscore the study’s importance.
“The Research Grants program at the American Foundation for Suicide Prevention began in the late 1980s at a time when there had been very little investment in research on suicide risk and prevention,” said Moutier. “Over the years, as AFSP has grown, our priority on funding research has helped to grow a mature field of suicide researchers, like Dr. Alan Schatzberg, who is a leader in the field and who mentors others. We are pleased with the results of his important study, one of the first to show the effectiveness of a pharmacologic intervention in helping maintain and build on ketamine’s anti-suicidal effects in an at-risk population."
The authors noted that the study was relatively small and excluded individuals with substance use disorders, meaning additional research is needed to confirm the findings, determine optimal treatment duration, and better understand longer-term safety and effectiveness. They also note that further study is needed on tapering and follow-up strategies.
The article, “Low-Dose Buprenorphine Following Ketamine Treatment for Suicidal Ideation in Major Depressive Disorder: A Randomized, Double-Blind, Placebo-Controlled Trial,” can be found at the American Journal of Psychiatry.
In addition to a Focus Grant from the AFSP, the study was supported by funding from the Pritzker Foundation, the National Institute on Drug Abuse, and Stanford’s Clinical and Translational Science Award Program.
American Psychiatric Association
The American Psychiatric Association, founded in 1844, is the oldest medical association in the country. The APA is also the largest psychiatric association in the world with more than 40,400 physician members specializing in the diagnosis, treatment, prevention and research of mental illnesses. APA’s vision is to ensure access to quality psychiatric diagnosis and treatment. For more information, please visit www.psychiatry.org.
Journal
American Journal of Psychiatry
Method of Research
Randomized controlled/clinical trial
Subject of Research
People
Article Title
Low-Dose Buprenorphine Following Ketamine Treatment for Suicidal Ideation in Major Depressive Disorder: A Randomized, Double-Blind, Placebo-Controlled Trial
Article Publication Date
19-May-2026
