Researchers from the University of South Australia have found a causal genetic relationship between higher genetic risk for major depressive disorder and greater susceptibility to 20 distinct but seemingly unrelated physical illnesses.
The illnesses are broad-ranging, including asthma, high cholesterol, coronary artery disease, urinary tract disorders, gastroenteritis, bacterial e. coli infections and inflammation of the esophagus.
Researchers analyzed data from 337,536 U.K. Biobank participants, an international Britain-based health data resource. It contains information on 500,000 individuals who’ve agreed to have their health metrics tracked for research purposes.
While other studies have identified links between depression and individual diseases, this study was the first to use a particular method known as MR-PheWAS (Mendelian randomization - phenome wide association) to screen for more definitive causal links between major depression and 925 different diseases.
According to another study published in the journal World Psychiatry, Individuals with severe mental illness such as major depressive disorder, bipolar disorder and schizophrenia have not only much higher rates of physical illness than the general population. They may face significantly shorter life expectancies as well — as much as 13 to 30 years shorter.
The study, which was published in August in the journal Molecular Psychiatry, answers a longstanding “chicken and egg” question about whether physical illness leads to major depression or whether major depression causes physical illness, Anwar Mulugeta, genetics and bioinformatics research associate at the University of South Australia School of Health Sciences, said in a university press release.
The findings indicate a need to screen for and manage a defined set of potential comorbid (i.e. co-occurring) physical conditions in individuals with major depression, Mulugeta said.
Professor Elina Hyponnen, lead study author and director of the Australian Centre for Precision Health at the University of South Australia Cancer Research Institute, said that understanding the connection between disease and depression is crucial to providing the right support.
“The more we can look at the individual patient as a whole, the better their outcomes are likely to be,” Hyponnen said, adding that the study highlights the need to encourage healthy lifestyles and diet in those with major depression.
The exact mechanisms of genetic causation linking major depression with these 20 illnesses remains unknown.