Are Depression and Inflammation Related?


Depression is widespread, but its causes are little understood, despite a century or more of study.


About a hundred years ago psychiatrist Adolf Meyer posited a theory that psychiatric illnesses result from chronic physical infections. His observations of the effects of high fevers on the brain – hallucinations and delusions – led him to the belief that the inflammation that results from infection was a causative factor in the development of mental illness, including depression.

Fast forward to 2014, and the publication of a paper in the journal Biology of Mood and Anxiety Disorders by Turhan Canli, an associate professor of Biology and Radiology at Stony Brook University. In this paper, Canli asserts that depression should be thought of as an infectious disease, comparing some of the symptoms of illness – extreme tiredness, loss of appetite, increased sensitivity to pain, social withdrawal, apathy – with the symptoms of depression.

Canli is not alone in his beliefs. Over the last century there have been numerous studies that have linked depression with elevated levels of inflammatory response in the brain.

Most current depression treatment rests on the idea of imbalances within a group of neurotransmitters – serotonin, dopamine and norepinephrine - in the brain. Despite the development of a wide range of antidepressants that target these imbalances, depression remains a tough road for many.

Current Research

For this reason, scientists are again considering the possibility that inflammation in the brain might be the source of depression. A March 2015 article in the medical journal JAMA Psychiatry detailed a study , conducted primarily by a group of Toronto, Canada researchers, with findings that strongly support the concept of neuroinflammation triggering major depressive episodes (MDE.)

The Cleveland Clinic has also been looking at inflammation and depression. Specifically, they have been studying the influence stress has on causing certain proteins which have inflammatory properties to break through the barrier between the body and the brain, bringing this inflammation to the neurotransmitters in the brain.

The Future

Neurotransmitters have always been difficult to study, as they are present in minute quantities in the brain, and are generally released at different times of the day.

Increasingly sophisticated testing allows scientists to track markers of certain substances in blood or tissue that help them understand the composition of and relationship to various substances and chemical reactions within the brain. With this “second hand” approach, researchers can develop new hypotheses to test, which may lead them to new treatments.

It is too soon for doctors to begin simply prescribing anti-inflammatory drugs to treat depression. There are still many variables to consider when diagnosing and treating depression, including possible genetic indicators and the personal history of the patient. These studies do offer hope, however, of future treatments personalized to the specific triggers to depression within each patient.

Sources: National Public Radio , Cleveland Clinic and Current Psychiatry


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