Depression – an Inflammatory Disease?

SRxA’s Word on Health brings you a chicken and egg type conundrum to start your day.

Up to 40% of people who are chronically ill get depressed.  Depressed people are prone to a variety of medical illnesses including diabetes and coronary heart disease.

So which comes first?

A new meta-analysis from researchers at the University of Toronto, published last month in Biological Psychiatry, may provide the answer.

To determine whether pro-inflammatory cytokines play a role in the overlap between depression and inflammation-associated medical disorders, the Toronto group conducted a meta-analysis of 24 studies of cytokine levels in 438 unmedicated subjects with major depression and 350 medically and psychiatrically healthy controls.

They found that concentrations of two cytokines: tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-6 were significantly higher in depressed patients than in controls. The groups showed no significant differences in other interleukin levels.

IL-6 stimulates differentiation and proliferation of antibody secreting white blood cells while TNF-α  stimulates the release of other pro-inflammatory cytokines and inflammatory prostaglandins. In the brain, these substances result in increased cortisol production; and increased production of a substance that accelerates cell death.  This reduces the resilience of the brain and may contribute to the stress response that is characteristic of depression.

High levels of IL-6 and TNF-α  have also been correlated with depression in patients with cancerend stage kidney diseaseParkinson’s disease, stroke and a host of other non-infectious conditions.

The results of this study provide further evidence that depression is accompanied by activation of the inflammatory response system and contributes to the development and progression of physical illness.

Which begs the question – will anti-inflammatory drugs prove helpful in managing depression?

Although corticosteroids, used to treat inflammatory conditions, have an initial ‘pick me up’ effect in some patients, over time, the same drugs can provoke depression. Non-steroidal anti-inflammatory drugs (NSAIDs) could be another option, but they may also cause depressing side-effects such as  nausea, vomiting, diarrhea, constipation, headache, and drowsiness.

Word on Health suggests more studies are needed before we start popping more pills!