May 7, 2020
Natalie Momen and John McGrath
Many clinicians will have noticed that people with mental disorders seem to be at higher risk of also developing a range of general conditions. The presence of two or more disorders in a person is called “comorbidity”. Our research group, based at the National Centre of Register-based Research in Aarhus, Denmark, has been running a project aiming to improve our understanding of comorbidity in people with mental disorders. One of our previous studies showed that people with one type of mental disorder (e.g. a psychotic disorder) are more likely to subsequently develop additional mental disorders (e.g. substance use disorder). In our new paper “Association Between Mental Disorders and Subsequent Medical Conditions”, we wanted to describe the association between mental disorders (like depression, anxiety or bipolar disorder) and subsequent risk of a wide range of medical conditions (like high blood pressure, diabetes or cancer).
Using data from the nationwide Danish health registers, we found that people with most mental disorders had an increased risk of many medical conditions. For example, we looked at women with substance use disorders, which includes alcohol dependence. In Denmark, around 5% of women will be diagnosed with a substance use disorder in their lifetime. We compared women with substance us disorders with women of similar age who do not have them. We then looked at their risks of medical conditions which affect their gut, like liver disease or inflammatory bowel disease. We saw that women with substance use disorders were more than three times more likely to develop a condition of the stomach, intestine or liver compared to women without. Additionally, around 1 in 5 women with a substance use disorder will go on to be diagnosed with a condition of the gut over the next 15 years.
Understanding comorbidity in people with mental disorders is important. Another one of our studies found that people with mental disorders die younger than those without mental disorders. On average, remaining life expectancy after diagnosis in those with a mental disorder was about 10 years shorter for men and 7 years shorter for females compared with the general population of the same age. We were able to examine which conditions contributed to premature mortality in those with mental disorders. While suicide is a factor, in fact most of the premature mortality is related to general medical conditions (respiratory disorders, heart attacks, stroke, cancer etc).
As the IEPA knows well, many mental disorders tend to have their first onset in the second and third decade of life. Our study in the New England Journal of Medicine found that the risk of developing general medical conditions slowly increased in the first 15 years after onset. These disorders contribute to the premature mortality associated with mental disorders.
We have provided a detailed atlas of the association between mental disorders and general medical conditions. We believe that this information can help clinicians and their patients to better manage their health. For example, preventative measures, like smoking cessation, a healthy diet and adequate physical activity, can reduce the risk of this type of comorbidity.
The full paper can be found at:
Our project website, including links to all of our studies’ findings: www.nbepi.com
Natalie Momen, first author on the study, is a postdoctoral epidemiologist, working at the National Centre of Register-based Research, Aarhus University, Denmark. The research team, made up of epidemiologists, statisticians and clinicians, was lead by Professor John McGrath. Professor McGrath is a psychiatrist who has appointments at the University Of Queensland and the Queensland Brain Institute in Australia, and at Aarhus University.