Severe Depression Linked to Higher Risk of Physical Illness

People with severe or moderately severe depression were at increased risk of physical illness requiring hospital treatment, according to a prospective multi-cohort study.

Across three cohorts with a total of 240,433 people, individuals with self-reported severe or moderately severe depression had at least a 1.5-times higher risk of 29 nonoverlapping hospital-treated conditions across multiple organ systems when compared with individuals without depression, Philipp Frank, PhD, of the University College London, and coauthors reported in JAMA Psychiatry.

In one of the cohorts based in the U.K., the researchers found a robust association with physician-diagnosed depression for 25 of those conditions after adjusting for confounders (adjusted HR range 1.52-23.03).

Those associations included a range of conditions:

• Ischemic heart disease: HR 1.76 (95% CI 1.36-2.29)
• Osteoarthritis: HR 1.80 (95% CI 1.46-2.20)
• Bacterial infections: HR 2.52 (95% CI 1.99-3.19)
• Back pain: HR 3.99 (95% CI 2.96-5.38)
• Chronic obstructive bronchitis: HR 4.11 (95% CI 2.56-6.60)
• Diabetes: HR 5.15 (95% CI 2.52-10.50)
• Sleep disorders: HR 5.97 (95% CI 3.27-10.89)

"The most surprising finding from our paper was that depression was associated with such a large number of physical diseases," Frank told MedPage Today. "This finding suggests that the impact of depression on physical health is widespread, meaning that it is clearly not limited to a specific area of the body or a particular group of diseases."

"The biggest overall takeaway is the importance of considering depression as a risk factor for various physical illnesses and a target for somatic disease prevention and treatment," Frank added.

The largest absolute risk difference was the 9.8% greater risk of endocrine and related internal organ diseases with depression versus without depression (4-year incidence of 245 vs 147 per 1,000 persons, respectively), which was particularly seen in conditions like diabetes (HR 5.15, 95% CI 2.52-10.50) and kidney failure (HR 3.66, 95% CI 2.30-5.83).

Musculoskeletal diseases were an absolute 3.7% higher risk for those with depression (4-year incidence 91 per 1,000 persons), while cardiovascular diseases had an absolute risk difference of 3.9% (86 per 1,000 persons), particularly heart failure (HR 4.38, 95% CI 2.66-7.23).

The researchers also found evidence of a bidirectional relationship with severe or moderately severe depression for 12 conditions, including mood (HR 5.29, 95% CI 2.17-12.86) and sleep disorders (HR 5.97, 95% CI 3.27-10.89).

"Our research highlights the importance for healthcare professionals to be attentive to their patients' mental health. They should acknowledge the potential of depression to worsen or contribute to an array of physical health issues," Frank said. "Clinicians should also be aware of the bidirectional relationships between depression and certain physical illnesses, as effectively treating one might improve the other."

His group did note a few limitations of the analyses. For example, they were not able to determine causal inference, because the studies were observational and missing data may have hindered any conclusions about the direction of the associations. They also reported that the use of predefined common diseases and data-driven HR thresholds could mean the results of the study underestimated the true burden of hospitalization associated with depression.

For this prospective multi-cohort study, the primary analysis was conducted using data from the U.K. Biobank (a population-based study), and two subsequent analyses were conducted using two cohorts in Finland: the population-based Health and Social Support Study and the Finnish Public Sector Study, an occupational cohort.

In total, the researchers analyzed data from 130,652 individuals from the U.K. Biobank cohort (55% women; mean age 63 years at baseline) and 109,781 participants from the two Finnish cohorts (79% women; mean age 42).

In the U.K. Biobank cohort, the researchers used the Patient Health Questionnaire-9 (PHQ-9) to assess depression and previously established indicators to determine the severity and duration of depression. In the Finnish cohorts, they used available measures for self report of physician-diagnosed depression and histories of recorded hospitalizations that included depression diagnoses based on ICD-10 codes taken from national hospital admission registers.

"Doctors should be vigilant about screening for depression and other mental health issues in patients with these conditions, as well as monitoring the potential impact of depression on disease management, adherence to treatments, and overall health outcomes," Frank said.

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