The biological approach to ocd

Concordance rate

a measure of genetic similarity

dopamine

key neurotransmitter in the brain which effects motivation and drive

gene

part of the chromosome of an organism that carries information in the form of DNA

genetics and OCD

• Genes are involved int he individuals vulnerability to developing OCD

• Lewis 1963 found that 37% of suffers had a parent with the disorder and 21% had a sibling

• This demonstrates a biological influence however environmental stress is necessary to trigger the condition (diathesis stress model)

Genetic explanation- candidate genes

researchers have identified genes that create a vulnerability for OCD

Genetic explanations- OCD is polygenic

It is not caused by a single gene but several

Taylor 2013 has found evidence of up to 230 different genes being involved

Different types of OCD

one group of genes may cause OCD in one person but a different group of genes may cause it for another which means that the origin and the cause are different amongst individuals this is called (aetiologically heterogeneous)

Genetic explanation

• Mental disorders are inherited

• We inherit specific genes from our parents

• The COMPT gene may contribute to OCD it regulates the production of the neurotransmitter dopamine which is associated with the disorder

• The SERT gene- this is responsible for levels of serotonin. Lower levels are associated with OCD. A study on two unrelated families found a mutation in this gene ; where six of the seven family members had the disorder

A02 family and twin studies

Nestadt 2000- 80 patients with OCD 343 of their first degree relatives were compared with 73 controls without mental illness and 300 of their relatives

Those with a first degree relative had a 5x greater likelihood of developing the disorder compared to the general population

A02 Twins

billet 1998- MZ twins were far more likely 2x to. Develop OCD if eir identical twin had compared to DZ twins

However, concordance rates are never 100% so environmental factors must play a role in the onset of the disorder

Co morbidity

more than one disorder at once not one gene cause OCD as a predisposing factor

Environmental risk factors

cromer 2007 found that over 50% of OCD patients had experienced a traumatic event in their past and that OCD was most severe in those with more than one trauma. This suggests that OCD cannot be entirely genetic origin

Tourettes and other disorders

Other disorders display obsessional behaviours- tourette’s autism anorexia depression. Two out of every three patients with OCD also suffer from depression