Researchers found that some combinations of chronic illnesses, particularly cardiometabolic ones like diabetes and heart disease, could more than double the likelihood of a future depression diagnosis.
They followed people’s health data for over 10 years. They found that eight in 100 people with the highest risk combinations of chronic illnesses developed depression in that time, compared with four in 100 people without physical conditions.
Multimorbidity, when patients live with two or more chronic conditions, continues to put pressure on healthcare systems. The researchers say the findings highlight the need for integrated care models that address both mental and physical health.
Physical illnesses influence the risk of depression
The study was funded by the Medical Research Council and the National Institute for Health Research.
It 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, a condition that often goes underdiagnosed in people managing long-term physical diseases.
Participants were aged between 37 and 73 years old and had at least one chronic physical condition, but no history of depression.
The scientists used statistical clustering techniques to group individuals by their physical illness profiles and tracked how these clusters related to later diagnoses of depression.
Complex mix of conditions and depression
One group, which included people experiencing the highest rates of physical illness, also 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.
Greater depression risk in high-risk groups
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.
Anticipating depression in people with physical illness
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 a period of time the researchers showed that physical illnesses preceded the depression.