The human body is an amazing and very complex organism. Because of advancements in genetic research, we now know that many diseases and disorders have a genetic component. Therefore, it should come as no surprise that psychiatric disorders such as obsessive-compulsive and related disorders (OCRDs) are believed to have a genetic component as well. Furthermore, the intricacies of our bodies, especially our brains, are presumed to be involved in the origins and maintenance of OCRDs. Research suggests these disorders most likely have a genetic or familial link. This means family members often have the same disorder, and this frequency occurs more often than random chance. However, the research has not yet identified the precise nature of this link.
In addition, at birth, there are observable temperamental differences among individuals. These differences appear to be a function of genetics. For example, some babies are much more sensitive to stimulation and stress than are other babies. These differences remain as the child matures. People born with these extra-sensitive temperaments may be at a greater risk for developing an OCRD later in life because their nervous system is more easily aroused. Consequently, people with these extra-sensitive temperaments are prone to experience emotions with greater intensity than are people with less-sensitive temperaments. As discussed in the diagnosis section, the various obsessive-compulsive symptoms are often triggered in response to uncomfortable emotions (e.g. anxiety). Therefore, persons with extra-sensitivity are at greater risk for developing an OCRD.
Although inconclusive, evidence suggests the brains of people with OCRD are different from people without OCRD. For example, on average, people with body dysmorphic disorder have more white matter in their brains. There are also differences in amygdalo-hippocampal formation in people with obsessive-compulsive disorder and Trichotillomania (hair-pulling). Likewise, differences can be observed in the fronto-limbic circuits of people with hoarding disorder.