Is there a common mechanism of serotonin dysregulation in anorexia nervosa and obsessive compulsive disorder?

Numerous studies have documented increased rates of comorbidity in patients with anorexia nervosa (AN) or obsessive compulsive disorder (OCD). The interaction of many possible factors influences this comorbidity, but one possible explanation involves the neurotransmitter serotonin, which is widely distributed in the brain and has been implicated in a number of psychological behaviours. Although low serotonin levels have been found in patients with impulsive and aggressive behaviour, high levels have been correlated with obsessive and compulsive behaviour. In an attempt to further our understanding of this relationship, a large number of studies have measured serotonin levels throughout different stages of illness in both AN and OCD; furthermore, serotonin challenge studies and drug treatment trials have provided further support for this theory. This paper discusses the evidence supporting the view that the obsessive behaviour characteristic of AN and OCD may be partially due to a dysregulation in the serotonergic system.