Psychology In The News | Depression and the Gender Gap

Two pieces of recently published research have explored the impact of gender on the incidence of depression in young people.

Depression affects 280 million people globally, with women experiencing it at twice the rate of men—a pattern that begins during adolescence. New research by Nikkheslat et al (2025) has investigated the biological mechanisms behind this sex difference by examining the ‘kynurenine pathway’ in teenagers.

This pathway processes tryptophan (an amino acid found in foods) through two routes: one producing neuroprotective chemicals (kynurenic acid) and another producing neurotoxic chemicals (quinolinic acid). The study examined 150 Brazilian adolescents aged 14-16 across three groups: low depression risk, high risk, and diagnosed depression.

The researchers discovered that teenagers with higher depression risk or diagnosis had lower levels of neuroprotective kynurenic acid, with the reduction most pronounced in females. This may explain why girls experience higher depression rates.

Follow-up assessments three years later revealed that female adolescents with persistent depression had higher levels of neurotoxic metabolites than those who recovered, suggesting that increased neurotoxic activity might make depression more difficult to overcome.

The researchers state that identifying these biological pathways could help build a clearer picture of adolescent depression and potentially lead to more targeted interventions, including medication and lifestyle changes.

A further study compared the trajectories of depressive symptoms in adolescents aged 11-16 years from London and Tokyo between 2014 and 2020. Researchers used the Short Mood and Feelings Questionnaire (SMFQ) to measure depressive symptoms at three different time points.

In both cities, there was a widening gender gap in depressive symptoms as teenagers aged, but with notable differences between locations. The gender difference emerged earlier in London (by age 11-12) than in Tokyo (between 11-14 years). By age 16, the disparity between boys and girls in London was approximately twice that observed in Tokyo.

Girls in London suffered the most from depression, with their symptoms increasing at a rate four times faster than Tokyo girls. Interestingly, symptoms decreased in Tokyo boys while slightly increasing in London boys, with the latter following a similar trajectory to Tokyo girls.

Dr. Knowles suggests that these findings challenge the narrative that girls are inherently more prone to emotional health struggles. Despite the UK ranking much higher (15th) than Japan (125th) on the Global Gender Gap Index, researchers noted social factors not captured by these metrics, including earlier assumption of adult responsibilities by London girls and lower crime rates in Tokyo, may contribute to these differences.

ANSWER THE FOLLOWING QUESTIONS!

1. What biochemical finding from Nikkheslat et al.'s study might explain why females have higher rates of depression?
2. How do the findings from both studies contribute to our understanding of the nature-nurture debate regarding depression in adolescents?
3. What implications might the kynurenine pathway research have for developing gender-specific approaches to depression treatment?
4. How might a psychologist using the diathesis-stress model explain the different patterns of depression observed between London and Tokyo adolescents?
5. The second study used something called the Short Mood and Feelings Questionnaire (SMFQ) what concerns might there be about measuring mood using this questionnaire, across two different cultures?

Challenge: how would you overcome the issue of using the same questionnaire (SMFQ) to measure mood across two different cultures?

References:

Naghmeh Nikkheslat et al Sex-Specific Alterations of the Kynurenine Pathway in Association With Risk for and Remission of Depression in Adolescence. Biological Psychiatry, 2025; DOI: 10.1016/j.biopsych.2024.11.020 (accessed 1.4.25)

Gemma Knowles 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; 9 (4): 224 DOI: 10.1016/S2352-4642(25)00059-8 (accessed 1.4.25)

Image from: https://www.kcl.ac.uk/news/gen... (accessed 1.4.25)