4.7 The biological approach to explaining OCD Flashcards
genetic explanations of OCD?
COMT - low activity of this gene causes high dopamine levels
SERT/5-HTT - one version causes poor serotonin transport. low serotonin is a risk factor for OCD
Diathesis-stress - genes make you vulnerable, but something needs to ‘trigger’ illness
neurological explanations of OCD?
neurotransmitters:
- high dopamine doses led to OCD-like behaviour in animals (Szechtman et al. 1998)
- SSRIs help with OCD, so low serotonin must be a factor
brain circuits - supported by PET scan studies
- frontal cortex decided what’s ‘dangerous’
- the caudate nucleus filters out low-level warnings
- if this is damaged, even minor things get through, this is called the ‘worry circuit’
what is meant by concordance rate? can you describe an example?
a measure of genetic similarity.
In a sample of, for example, 100 twin pairs, one twin of each pair has a phobic disorder.
The number of times their other twin also shows the the illness determines the concordance rate, so if 40 have phobic disorder than the concordance rate is 40%
what is dopamine?
one of the key neurotransmitters in the brain, with effects on motivation and ‘drive’
what is a gene?
a part of the chromosome of an organism that carries information in the form of DNA
what is a neurotransmitter?
chemical substances that play an important part in the workings of the nervous system by transmitting nerve impulses across a synapse
summarise the genetic explanations of OCD
COMT gene - one allele more common in OCD, creates high levels of dopamine
SERT gene - one allele more common in a family with OCD, creates low levels of serotonin
diathesis stress - same genes linked to other disorders or no disorder at all, therefore genes create a vulnerability
summarise the neural explanations of OCD
dopamine levels high in OCD - linked to compulsive behaviour in animal studies
serotonin levels low in OCD - antidepressants that increase serotonin most effective
worry circuit - damaged caudate nucleus doesn’t suppress worry signals from OFC to thalamus
serotonin and dopamine linked to activity in these parts of the frontal lobe
evaluate the biological approach to explaining OCD
studies of first-degree relatives - 5 times greater risk of OCD if relative has OCD
twin studies - twice as likely to have OCD if twins are MZ
environmental component - concordance rates never 100%, type of OCD is not inherited
genes are not specific to OCD - also linked to tourettes, autism, anorexia i.e obsessive-type behaviour
research support for genes and OFC - OCD patients and family members more likely to have reduced grey matter in OFC (Menzies et al)
real world application - genes may be blocked or modified, genetic explanations lull people into thinking there are simple solutions
alternative explanations - relevance of two-process model supported by success of SD-like therapy, called ‘exposure and response prevention’ (Albucher et al)
