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A new study published in The Lancet Child & Adolescent Health has found a significant disparity in teenage depression levels between London and Tokyo, with the gender gap in London being twice as large as in Tokyo by the age of 16.
Researchers from King’s College London compared data from the Tokyo Teen Cohort (TTC) and the Resilience Ethnicity and Adolescent Mental Health (REACH) cohorts from South London, both of which tracked the mental health of 11 to 16-year-olds between 2014 and 2020. Using the Short Mood and Feelings Questionnaire (SMFQ) to measure depressive symptoms, the study revealed distinct patterns in both cities.
In London, the gender difference in depressive symptoms emerged earlier, around ages 11-12, and increased at a faster rate compared to Tokyo. By age 16, the gap between boys and girls in London was double that of Tokyo. Specifically, the average rate of change in depressive symptoms per year in London girls was approximately four times greater than among girls in Tokyo.
Notably, the study found that while depressive symptoms in Tokyo boys declined between ages 11 and 16, they slightly increased in London boys, mirroring the trajectory of girls in Tokyo.
“Our study suggests that from around early adolescence onward girls have higher levels of depression than boys in both Tokyo and London, but the disparity is larger, starts a bit earlier, and increases at a faster rate in London,” said Dr. Gemma Knowles, the study’s first author.
The researchers also highlighted that the trajectory for boys in London closely resembled that of girls in Tokyo, challenging common narratives about inherent gender differences in mental health.
While the Global Gender Gap Index (GGGI) ranks the UK higher than Japan in terms of gender equality, the study suggests that social factors not captured by such indices may play a significant role. Young co-researchers from both cities pointed to potential influences such as earlier assumption of adult responsibilities by girls in London and lower levels of violence and crime in Tokyo. Socioeconomic factors, such as the period of austerity in the UK, were also considered.
“This is a complex area with a multitude of possible factors that may contribute to the difference between girls and boys and between the two places,” Dr. Knowles stated. “We need to better understand the social contexts and experiences that give rise to gender inequalities in mental health and the conditions that support teenage girls to thrive.”
The study also addressed the validity of using the SMFQ across different demographics, concluding that any observed differences in scores likely reflect genuine variations in depressive symptoms rather than measurement inconsistencies.
More information: Knowles G. et al. Trajectories of depressive symptoms among young people in London, UK, and Tokyo, Japan: a longitudinal cross-cohort study., The Lancet Child & Adolescent Health (2025). DOI: 10.1016/S2352-4642(25)00059-8
Disclaimer: This news article is based on the provided study and aims to accurately reflect the research findings. It is important to note that mental health is a complex issue influenced by numerous factors, and this study provides one perspective on the differences observed between London and Tokyo. Further research is necessary to fully understand the underlying causes of these disparities.
