Obsessive-Compulsive Disorder (OCD)
Origins of OCD
Although the exact cause of OCD is unknown, a combination of environmental, cognitive, and biological factors appear to be involved. A deficiency of serotonin (a neurotransmitter in the brain that assists with the transmission of electrical messages among nerve cells) has been proposed as at least a partial explanation. Serotonin deficiency has also been implicated in anxiety, depression, and other psychiatric disorders. Various neuroimaging studies also suggest that an electrical dysfunction in certain brain regions may contribute to OCD (Whiteside 2004). This observation is supported by comparisons of brain activity taken by single photon emission computed tomography and positron emission tomography from healthy controls and people with OCD. Investigators have also suggested that OCD, tic disorders, or both may be caused by an autoimmune response to streptococcal bacteria in some susceptible children (Arnold 2001).
Genetic factors may also play a role in the development of OCD. People with a first-degree relative (ie, parent, sibling) with OCD, for example, have a five-fold greater risk than others of developing the condition (Nestadt 2000). A comprehensive review of studies of twins shows that in children, genetic factors account for 45 to 65% of the risk of developing OCD (van Grootheest 2005). In another study, researchers identified a gene variant that doubles a person’s risk of developing OCD (Hu 2006).