Brain Serotonin Deficiency
Brain serotonin deficiency is a heterogeneous condition whose etiology remains unknown in the majority of cases. Strong evidence supports a major role for brain serotonin deficiency in common conditions such as depression and other psychiatric and cognitive disorders, which are probably due to interactions between genetic and environmental factors. Mendelian monogenic conditions leading to brain serotonin deficiency have also been identified, but they are rare. These diseases are associated with defects in other neurotransmitters (primarily dopamine), and it is difficult to link serotonin deficiency with specific neurological syndromes. Secondary serotonin deficiency is also common. In adults, when serotonin deficiency is thought to contribute to neurological symptoms such as sleep disturbance and alterations in behavior, treatment with serotonin precursors may be useful.