biological approach to explaining OCD Flashcards
genetic explanations - COMT gene
regulates production of dopamine that has been implicated in OCD.
one form of COMT gene has been found to be more common in OCD patients than people without it - produces lower activity of COMT gene and higher levels dopamine
genetic explanations - SERT gene
creates low levels of serotonin which are implicated in OCD.
one study found mutation of SERT gene in 2 unrelated families where 6/7 family members had OCD
genetic explanations - diathesis stress
genes such as SERT gene are implicated in a number of other disorders - each individual gene only creates vulnerability for OCD as well as other conditions.
other factors affect what condition develops - some people could possess COMT or SERT gene variations but suffer no ill effects
neural explanations - abnormal levels of neurotransmitters
dopamine levels abnormally high in people with OCD - based on animal studies
high doses of drugs that enhance levels of dopamine induce stereotyped movements resembling behaviour found in OCD patients
low levels of serotonin - antidepressant drugs that increase serotonin activity show reduction in OCD symptoms.
neural explanations - abnormal brain circuits
caudate nucleus normally suppresses signals from orbitofrontal cortex (OFC) which then sends signals to thalamus about things that are worrying.
when caudate nucleus is damaged, it fails to suppress minor worry signals and thalamus is alerted which sends signals back to the OFC acting as a worry circuit - supported by PET scans of patients with OCD taken while symptoms are active - scans show heightened activity in OFC
evaluation - family and twin studies
evidence for genetic basis of OCD
nestadt et al - identified 80 patients with OCD and 343 of their first degree relatives and compared them with 73 control patients without mental illness and 300 of their relatives
people with first degree relative with OCD had 5x greater risk of having it themselves at some time in their lives.
evaluation - real world application
mapping of human genome has led to hope that specific genes could be linked to particular mental and physical disorders
if one parent-to-be has COMT gene, mother’s fertilised eggs could be screened giving parents choice of whether or not to abort eggs with the gene, gene therapy may produce means of turning certain genes off so that disorder isn’t expressed
but this has ethical issues
evaluation - reductionist
cromer et al - over half of OCD patients in their sample had traumatic event in past, and that OCD was more severe if there was more than one trauma - theory is reductionist as it states OCD is mostly biological. However, it is not entirely genetic and so may be more productive to focus on environmental causes as we are more able to do something about these.
