Serotonin levels, pain threshold, and fibromyalgia symptoms in the general population.

Serum serotonin levels are significantly lower in persons with FM compared to those without FM, but the range of values is wide. Difficult to explain correlations with reversed directions are noted for tender point count, dolorimetry, depression, and anxiety among those with FM. Serotonin is not correlated with any clinical variables in the general population, and separate pain groups cannot be distinguished.