- Lewis (1936) observed that of his OCD patients, 37% had parents with OCD and 21% had siblings with OCD.
- According to the diathesis-stress model, certain genes leave some people more likely to suffer a mental disorder but it is not certain - some environmental stress (experience) is necessary to trigger the condition.
Candidate genes: Create vulnerability for OCD. 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 efficiency of transport of serotonin across synapses.
OCD is polygenic: Several genes are involved. Taylor (2013) analysed findings of previous studies and found evidence that up to 230 different genes may be involved in OCD. Genes that have been studied in relation to OCD include those associated with the action of dopamine as well as serotonin, both neurotransmitters believed to have a role in regulating mood.
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 -- aetiologically heterogeneous, meaning that the origin (aetiology) of OCD has different causes (heterogeneous). May also be as a result of particular genetic variations…