Genetic and physiological. The rate of 0CD among first-degree relatives of adults with
OCD is approximately two times that among first-degree relatives of those without the disorder; however, among first-degree relatives of individuals with onset of 0CD in child- hood or adolescence, the rate is increased 10-fold. Familial transmission is due in part to genetic factors (e.g., a concordance rate of 0.57 for monozygotic vs. 0.22 for dizygotic twins).
Dysfunction in the orbitofrontal cortex, anterior cingulate cortex, and striatum have been most strongly implicated.
0CD occurs across the world. There is substantial similarity across cultures in the gender distribution, age at onset, and comorbidity of OCD. Moreover, around the globe, there is a similar symptom structure involving cleaning, symmetry, hoarding, taboo thoughts, or fear of harm. However, regional variation in symptom expression exists, and cultural factors may shape the content of obsessions and compulsions.
Males have an earlier age at onset of OCD than females and are more likely to have co- morbid tic disorders. Gender differences in the pattern of symptom dimensions have been reported, with, for example, females more likely to have symptoms in the cleaning dimen- sion and males more likely to have symptoms in the forbidden thoughts and symmetry di- mensions. Onset or exacerbation of 0CD, as well as symptoms that can interfere with the mother-infant relationship (e.g., aggressive obsessions leading to avoidance of the infant), have been reported in the peripartum period.
Suicidal thoughts occur at some point in as many as about half of individuals with OCD.
Suicide attempts are also reported in up to one-quarter of individuals with 0CD; the pres- ence of comorbid major depressive disorder increases the risk.
0CD is associated with reduced quality of life as well as high levels of social and occupa- tional impairment. Impairment occurs across many different domains of life and is asso- ciated with symptom severity. Impairment can be caused by the time spent obsessing and doing compulsions. Avoidance of situations that can trigger obsessions or compulsions can also severely restrict functioning. In addition, specific symptoms can create specific obstacles. For example, obsessions about harm can make relationships with family and friends feel hazardous; the result can be avoidance of these relationships. Obsessions about symmetry can derail the timely completion of school or work projects because the project never feels “just right,” potentially resulting in school failure or job loss. Health consequences can also occur. For example, individuals with contamination concerns may avoid doctors’ offices and hospitals (e.g., because of fears of exposure to germs) or develop dermatological problems (e.g., skin lesions due to excessive washing). Sometimes the symptoms of the disorder interfere with its own treatment (e.g., when medications are con- sidered contaminated). When the disorder starts in childhood or adolescence, individuals may experience developmental difficulties. For example, adolescents may avoid socializ- ing with peers; young adults may struggle when they leave home to live independently.
The result can be few significant relationships outside the family and a lack of autonomy and financial independence from their family of origin. In addition, some individuals with
OCD try to impose rules and prohibitions on family members because of their disorder (e.g., no one in the family can have visitors to the house for fear of contamination), and this can lead to family dysfunction.