The old belief that OCD was the result of adverse experiences or poor parenting has given way to the growing evidence that biological factors are a primary contributor to the disorder. The fact that OCD patients respond well to specific medications that affect the brain-chemical or neurotransmitter serotonin suggests the disorder has a neurobiological basis. For that reason, OCD is no longer simply attributed to the attitudes a patient learned in childhood--for example, an inordinate emphasis on cleanliness, or a belief that certain thoughts are dangerous or unacceptable. Instead, the search for causes now focuses on the interaction of neurobiological factors and environmental influences. OCD is sometimes accompanied by depression, eating disorders, substance abuse disorder, a personality disorder, tic or Tourette's disorder, attention deficit disorder , or another of the anxiety disorders. Co-existing disorders can make OCD more difficult both to diagnose and to treat. In an effort to identify specific biological factors that may be important in the onset or persistence of OCD, investigators at the IWK-Grace Health Center in Halifax, and many other centers in North America, have used brain scans (SPECT in Halifax, and SPECT and PET in other centers) to study the brains of patients with OCD. Several groups or investigators have obtained findings from these scans suggesting that OCD patients have patterns of brain activity that differ from those people without psychiatric disorder. Brain-scan studies of OCD showing abnormal brain-chemical activity in regions known to play a role in certain neurological disorders suggest that these areas may be crucial in the origins of OCD. There is also evidence that medications and behaviour therapy induce changes in the brain as clinical improvement occurs. Symptoms of OCD are seen in association with some other neurological disorders. There is an increased rate of OCD in people with Tourette's syndrome , an illness characterized by tics: involuntary movements and vocalizations. Investigators are currently studying the hypothesis that a genetic relationship exists between OCD and the tic disorder. Another illness that may be linked to OCD is trichotillomania (the repeated urge to pull out scalp hair, eyelashes, or eyebrows). Genetic studies of OCD and other related conditions may enable scientists to pinpoint the genetic and molecular basis of these disorders. For more information concerning Obsessive-Compulsive Disorder, please return to the main page Please note that all above links to various homepages, with the exception of depression, are to sites, some official, that were not created by myself, but are included in hopes of helping those who may be interested in obtaining further information on the subjects. Thank-you!^_^