Biological explanations have two major assumptions:
- Individuals possess a genetic predisposition to develop anxiety that could take the form of OCD
- Anxiety is caused by an abnormality within neurochemicals or actual structure of the brain.
Genetic research into the prevalence of OCD aims to isolate a familial genetic link that increases the tendency to develop OCD. Research generally focusses on family and twin studies.
First-degree relatives e.g. father, sister etc. share on average 50% of your genome. To investigate the genetic transmission of OCD, there is a comparison made between relatives of diagnosed cases of OCD and relatives of controls:
- Pauls et al  found a prevalence of up to 10% in first-degree relatives of those with OCD in comparison to only a 2% prevalence in the general population
- Nestadt et all  80 patients with OCD were compared with 73 patients without a mental illness and found that first-degree relatives of those with OCD had a risk of 11.7% of developing OCD at some point in their lives. Contrasting with that first degree relatives of patients without OCD only have a risk of 2.7% in the onset of OCD.
Twin studies estalish genetic links…