A new study shows that some combinations of chronic diseases could more than double the likelihood of a future depression diagnosis
Researchers from the University of Edinburgh followed people’s health data for over ten years and were funded by the Medical Research Council and the National Institute for Health Research. The team looked at how multiple long-term chronic diseases are connected to a greater risk of developing depression.
Previous multimorbidity research often focused on physical disease, but the links between physical and mental health are increasingly recognised as necessary.
How does physical illness influence depression?
The researchers used data from more than 142,000 people in the UK Biobank study to examine how physical illnesses interact to influence the risk of depression. This condition often goes underdiagnosed in people managing long-term chronic diseases.
Participants were aged between 37 and 73 years old and had at least one chronic illness but no history of depression. Participants attended a baseline assessment during 2006–2010, which collected data on demography, lifestyle habits, health conditions, and physical and laboratory measurements.
The scientists used statistical clustering techniques to group individuals together by their chronic disease profiles and tracked how these clusters related to later diagnoses of depression.
One group included people experiencing the highest rates of chronic illness, and the findings showed the highest risk of developing depression. This group had no single dominant illness but rather a complex mix of issues.
People with both heart disease and diabetes were also found to be at high risk, as were those with chronic lung conditions like asthma or chronic obstructive pulmonary disease. Liver and bowel conditions also showed a noticeable link to depression in both men and women.
Women with joint and bone problems, such as arthritis, were particularly affected, but this pattern was not as prominent for men.
Inspiring other researchers to study the link between physical and mental health conditions
In the highest-risk groups, and after adjusting for other differences between groups, the chance of developing depression was up to 2.7 times greater than in people without physical conditions.
While the biological burden of illness may play a role, researchers say social and systemic factors could also help explain why physical multimorbidity leads to worse mental health outcomes.
Lauren DeLong, lead author from the University of Edinburgh’s School of Informatics, said: “We saw clear associations between physical health conditions and the development of depression, but this study is only the beginning. We hope our findings inspire other researchers to investigate and untangle the links between physical and mental health conditions.”
Professor Bruce Guthrie, from the University of Edinburgh’s Advanced Care Research Centre, said: “Healthcare often treats physical and mental health as completely different things, but this study shows that we need to get better at anticipating and managing depression in people with physical illness.”
Since the study was observational, it cannot prove causation, but by tracking the data over time, the researchers showed that physical illnesses preceded the depression.
