Serotonin levels may clarify unexplained pain

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A newly-discovered biological mechanism could explain heightened somatic awareness, in which people experience pain that has no physiological explanation.

Patients with heightened somatic awareness often experience unexplained symptoms—headaches, sore joints, nausea, constipation, or itchy skin—that cause emotional distress, and are twice as likely to develop chronic pain.

The condition, associated with illnesses such as fibromyalgia, rheumatoid arthritis, and temporomandibular disorders, is thought to have a psychological origin.

“Think of the fairy tale of the princess and the pea,” says Samar Khoury, a postdoctoral fellow at the Alan Edwards Centre for Research on Pain at McGill University.

“The princess in the story had extreme sensitivity where she could feel a small pea through a pile of 20 mattresses. This is a good analogy of how someone with heightened somatic awareness might feel; they have discomforts caused by a tiny pea that doctors can’t seem to find or see, but it’s very real.”

Thanks to an existing study on genetic association, Khoury and her colleagues might have found the elusive pea that explains somatic awareness.

The researchers used data available through the Orofacial Pain: Prospective Evaluation and Risk Assessment cohort that demonstrates that patients who suffer from somatic symptoms share a common genetic variant. The mutation leads to the malfunctioning of an enzyme critical for the production of serotonin, a neurotransmitter with numerous biological functions.

“We believe that this work is very important to patients because we can now provide a biological explanation of their symptoms,” says Luda Diatchenko, a professor in the Faculty of Dentistry and lead author of the paper in Annals of Neurology.

“It was often believed that there were psychological or psychiatric problems, that the problem was in that patient’s head, but our work shows that these patients have lower levels of serotonin in their blood.”

The results of the study lay the groundwork for the development of animal models that could better characterize the molecular pathways in heightened somatic awareness. Above all, Diatchenko and Khoury hope the work will pave the way for treatment options.

“The next step for us would be to see if we are able to target serotonin levels in order to alleviate these symptoms,” says.

The Canadian Institutes of Health Research, Natural Sciences and Engineering Research Council of Canada, the National Institutes of Health, and the National Institute of Dental and Craniofacial Research.

Source: McGill University