OCD is a good example of a condition that may be largely understood as biological in nature
Genes are involved in an individual vulnerability to OCD - Lewis observed that 37% of his patients with OCD had parents with OCD and 21% had siblings with OCD, suggesting that COD runs in families
According to the diathesis-stress model certain genes leave some people more likely to develop a mental disorder
Some environmental stress is necessary to trigger the condition
Candidate genes
Researchers have identified genes which create vulnerability for OCD called candidate genes
Some of these genes are involved in regulating the development of the serotonin system
E.g. the gene 5HT1-D beta is implicated in the transport of serotonin across synapses
OCD is polygenic
OCD is not caused by one single gene but by a combination of genetic variations that together significantly increase vulnerability
Taylor analysed findings of previous studies and found evidence that up to 230 different genes may be involved in OCD
These include those associated with the action of dopamine as well as serotonin
Different types of OCD
One group of genes may cause OCD in one person but a different group of genes may cause the disorder in another person
the term used to describe this is aetiologically heterogeneous, meaning that the origins of OCD may vary from one person to another
There is also some evidence to suggest that different types of OCD may be the result of particular genetic variations, such as hoarding disorder and religious obsession
