Recent research conducted by the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King’s College London has uncovered a connection between depression and the risk of depression, and specific inflammatory proteins in both boys and girls.
Inflammation triggers the release of proteins called cytokines into the bloodstream. While prior studies have shown that higher cytokine levels are linked to depression in adults, little was known about this relationship during adolescence.
The researchers delved into sex-specific distinctions in the association between inflammatory proteins and depression. Published in the Journal of Affective Disorders, the study revealed that different cytokines played a role in the risk and severity of depression in boys as opposed to girls. This investigation was part of the IDEA (Identifying Depression Early in Adolescence) project, supported by MQ Mental Health Research.
To assess inflammation, the team measured cytokine levels in the blood of 75 adolescent boys and 75 adolescent girls (aged 14-16) from Brazil. These 150 participants were divided equally into three groups: those at low risk of depression without current depression, those at high risk of depression without current depression, and those currently experiencing major depressive disorder (MDD).
The results indicated notable sex-specific differences in the specific inflammatory proteins associated with adolescent depression. Elevated levels of the cytokine interleukin-2 (IL-2) were linked to an increased risk and severity of depressive symptoms in boys but not in girls. Conversely, higher levels of IL-6 were connected to the severity of depression in girls but not boys. In boys, IL-2 levels were higher in the high-risk group compared to the low-risk group, and even higher in the group diagnosed with depression. This suggests that in boys, IL-2 levels in the blood could serve as an indicator for the onset of future depression.
Dr. Zuzanna Zajkowska, Postdoctoral Researcher at King’s IoPPN and the study’s first author, commented,
“This is the first study to show differences between boys and girls in the patterns of inflammation that are linked to the risk and development of adolescent depression. We found that the severity of depressive symptoms was associated with increased levels of the cytokine interleukin-2 in boys, but interleukin-6 in girls. We know more adolescent girls develop depression than boys and that the disorder takes a different course depending on sex so we hope that our findings will enable us to better understand why there are these differences and ultimately help develop more targeted treatments for different biological sexes.”
The adolescents were recruited from public schools in Brazil, and the risk of depression was assessed using a composite risk score based on 11 sociodemographic variables developed as part of the IDEA project. They completed various questionnaires regarding their emotional well-being, relationships, experiences, and mood, as well as underwent clinical assessments with a child and adolescent psychiatrist.
Senior author Professor Valeria Mondelli, Clinical Professor of Psychoneuroimmunology at King’s IoPPN, and theme-lead for Psychosis and Mood Disorders at the NIHR Maudsley BRC, emphasized,
“Our findings suggest that inflammation and biological sex may have combined contribution to the risk for depression. We know that adolescence is a key time when many mental disorders first develop and by identifying which inflammatory proteins are linked to depression and how this is different between boys and girls we hope that our findings can pave the way to understanding what happens at this critical time in life. Our research highlights the importance of considering the combined impact of biology, psychology, and social factors to understand the mechanisms underlying depression.”
This study is part of the Identifying Depression Early in Adolescence (IDEA) project led by Professor Valeria Mondelli at King’s IoPPN and funded by MQ Mental Health Research. The IDEA project aims to investigate how cultural, social, genetic, and environmental factors contribute to the development of depression in individuals aged 10-24 across various countries including the UK, Brazil, Nigeria, Nepal, New Zealand, and the USA. The study received support from the charity MQ Mental Health Research, UK Medical Research Council, and the Academy of Medical Sciences. Professor Valeria Mondelli is supported by the National Institute for Health and Care Research (NIHR) Maudsley Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King’s College London, as well as the Medical Research Council.
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