Obsessive-compulsive disorder (OCD) is characterized by unbidden obsessive thoughts and/or compulsory physical activities that are experienced as dysfunctional. Some OCD conditions are clearly genetic; research has demonstrated the significant role played by heredity. Some OCD conditions can be explained by certain information-processing deficits and/or biases; neuroimaging studies have revealed neural pathway disturbances. But the majority of OCD conditions are attributable to emotional and developmental causes.