Multiple biological pathways involving organs and the brain play a key part in physical and mental health, according to a new study from UCL, the University of Melbourne and the University of Cambridge.
The study, published in Nature Mental Health, analysed UK Biobank data from more than 18,000 individuals. Of these, 7,749 people had no major clinically-diagnosed medical or mental health conditions, while 10,334 had reported a diagnosis of either schizophrenia, bipolar disorder, depression or anxiety.
Using advanced statistical models, the researchers found a significant association between poorer organ health and higher depressive symptoms, and that the brain plays an important role in linking body health and depression.
The organ systems studied included the lungs, muscles and bones, kidneys, liver, heart, and the metabolic and immune systems.
Dr Ye Ella Tian, lead author of the study from the Department of Psychiatry at the University of Melbourne, said. "Overall, we found multiple significant pathways through which poor organ health may lead to poor brain health, which may in turn lead to poor mental health.
"By integrating clinical data, brain imaging and a wide array of organ-specific biomarkers in a large population-based cohort, for the first time we were able to establish multiple pathways involving the brain as a mediating factor and through which poor physical health of body organ systems may lead to poor mental health.
"We identified modifiable lifestyle factors that can potentially lead to improved mental health through their impact on these specific organ systems and neurobiology.
"Our work provides a holistic characterisation of brain, body, lifestyle and mental health."
Physical health was also taken into account, as well as lifestyle factors such as sleep quality, diet, exercise, smoking, and alcohol consumption.
Professor James Cole, an author of the study from UCL Computer Science, said: "While it's well-known in healthcare that all the body's organs and systems influence each other, it's rarely reflected in research studies. So, it's exciting to see these results, as it really emphases the value in combining measures from different parts of the body together."
Professor Andrew Zalesky, an author of the study from the Departments of Psychiatry and Biomedical Engineering at the University of Melbourne, said. "This is a significant body of work because we have shown the link between physical health and depression and anxiety, and how that is partially influenced by individual changes in brain structure.
"Our results suggest that poor physical health across multiple organ systems, such as liver and heart, the immune system and muscles and bones, may lead to subsequent alterations in brain structure.
"These structural changes of the brain may lead to or exacerbate symptoms of depression and anxiety, as well as neuroticism."
