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what does the biological approach assume?
mental disorders are related to the physical structure & functioning of the brain
psychopathology will be changed by the level of neurotransmitters
mental disorders should be investigated in the same way as mental illnesses
how should mental disorders be investigated?
classify using symptoms
identify underlying cause
prescribe appropriate treatment/therapy
what is the genetic explanation for OCD?
individuals inherit specific genes from their parents that are related to the onset of OCD
what genes are related to OCD?
COMT
SERT
what is the COMT gene?
involved in production of catechol-O-methyltransferase
regulates production of dopamine
how is dopamine related to OC?
high levels have been implicated to affect it
what evidence is there of the relationship between the COMT gene & OCD?
one form that produces lower activity of COMT & higher levels of dopamine has been found to be more common in OCD patients
what is the SERT gene also called?
5-HTT
how does the SERT gene affect OCD?
affects the transport of serotonin, leading to lower levels
what evidence is there of the relationship between the SERT gene & OCD?
a study found a mutation of the gene in two unrelated families where 6 out of 7 members had OCD
what is the diathesis-stress model?
there is no simple link between one gene & a complex disorder, so other facts must be considered
what other disorders is SERT gene implicated in?
depression
PTSD
what are the neural explanations of OCD?
neuroanatomical explanations
neurochemical
what is the neuroanatomical explanation for OCD?
abnormalities in areas in the frontal lobes
which areas in the frontal lobe are associated with OCD?
caudate nucleus in the basal ganglia
orbitofrontal cortex
what is the caudate nucleus supposed to do?
supress signals from the orbitofrontal cortex
what does the orbitofrontal cortex do?
send signals to the thalamus about worrying things
what happens when the caudate nucleus is damaged?
fails to suppress minor worry signals which creates a worry circuit
what evidence is there to support neuroanatomical explanations of OCD?
PET scans of OCD patients - taken while symptoms are active - heightened activity in OFC
Comer - serotonin plays key role in operation of OFC & caudate nuclei
high levels of dopamine lead to overactivity in basal ganglia
which hormones affect the frontal lobes?
serotonin & dopamine
what is the main neurotransmitter of the basal ganglia?
dopamine
what are neurochemical explanations for OCD?
abnormal levels of neural transmitters
what neurotransmitter is abnormally high in people with OCD?
dopamine
what evidence is there to support the link between dopamine and OCD?
animal studies - high doses of dopamine level enhancement drugs - induced stereotyped movements - resembled compulsions
what neurotransmitter is abnormally low in OCD patients?
serotonin
what evidence is there to support the link between serotonin & OCD?
antidepressant drugs that increase serotonin - reduce OCD symptoms
antidepressants with less effect on serotonin have no effect
what are the strengths of the biological approach to explaining OCD?
family studies - Nestadt et al - 80 patients with OCD + 343 relatives - 73 control - people with first degree relatives with OCD 5x risk of having it themselves
twin studies - meta-analysis - 14 studies - identical twins more than 2x likely to develop if other has it - concordance never 100%
Paul & Leckman - tourettes/depression - OCD is one form of expression of the same gene - obsessive behaviour in both - also autism & anorexia - not one specific gene - but, predisposing factor
research support - genetic link to abnormal levels of neurotransmitters - Menzies et al - MRI in OCD patients + family + control - OCD group had reduced grey matter in OFC - anatomical differences
real world application - one parent w COMT - mothers fertilised eggs can be screened - gives choice - alternative gene therapy may turn genes off - presumes a simple relationship
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