Obsessive-compulsive disorder is an intrusive condition that remains difficult to treat. This is due, in part, to the causes behind the disorder remaining hidden. Recent research, however, points the finger at brain inflammation.

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A common symptom of OCD is an obsession with cleanliness.

Obsessive-compulsive disorder (OCD) is characterized by uncontrollable obsessions and compulsions. Individuals with OCD may experience intrusive thoughts that produce anxiety or a need to repeat certain actions to relieve pent-up anxiety.

Common obsessions in OCD revolve around cleanliness, sexual taboos, aggressive thoughts, and symmetry.

Affecting an estimated 1 percent of people in the United States, around half of OCD cases are classed as severe.

OCD is generally treated with talking therapies - in particular, a type of cognitive behavior therapy called exposure and response prevention is recommended. There are also some medications available, with selective serotonin reuptake inhibitors being the most commonly prescribed. Currently, however, therapies only work for around 70 percent of OCD-affected individuals.

One of the biggest stumbling blocks to finding good treatments is that the physical causes of OCD are not known.

Inflammation and OCD

Breaking research published this week in JAMA Psychiatry takes a look at the role of brain inflammation in OCD. The senior author of the study is Dr. Jeffrey Meyer, head of the Neuroimaging Program in Mood & Anxiety at the Centre for Addiction and Mental Health in Toronto, Canada.

Inflammation is a natural process; it is a normal component of the immune response and a standard reaction to injury. However, if the level of inflammation is inappropriate or continues for too long, it can have negative consequences. For instance, in a number of diseases including rheumatoid arthritis and atherosclerosis, inflammation is heavily involved.

Growing evidence suggests that certain psychiatric conditions may involve neuroinflammation, some of which include major depressive disorder, schizophrenia, and bipolar.

Dr. Meyer and his team set out to understand whether inflammation in the brain could play a role in the development of OCD. To this end, they recruited 40 participants, comprising 20 with OCD and 20 without. Each was scanned using positron emission tomography that had been adapted to pinpoint and measure inflammation in the brain.

Specifically, the researchers were able to selectively dye microglia, which are cells that act as the nervous system's most prominent immune defense and which are activated during inflammation. The researchers measured levels of microglia in six brain regions known to be important in OCD, including the orbitofrontal cortex and anterior cingulate cortex.



Dr. Jeffrey Meyer

From inflammation to treatment

Another interesting finding was that individuals who reported the highest levels of stress when trying to stop themselves from acting on compulsions also had the highest levels of inflammation in a particular brain region.

As so many diseases involve inflammation, there are already a range of drugs designed to tackle it. Because these drugs already exist on the market, it may be a fruitful avenue of research in the hunt for more effective treatments for OCD.

"Medications developed to target brain inflammation in other disorders could be useful in treating OCD," Dr. Meyer says. "Work needs to be done to uncover the specific factors that contribute to brain inflammation, but finding a way to reduce inflammation's harmful effects and increase its helpful effects could enable us to develop a new treatment much more quickly."

Studies are now under way that examine the possibility of designing a blood marker test that could distinguish which patients would benefit most from anti-inflammatory drugs.

Although, as ever, more research is needed, this finding could mark a significant move forward in understanding and treating OCD.

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