AS PSYCHOPATHOLOGY - BIOLOGICAL APPROACH TO EXPLAINING AND TREATING OCD

Question 1

Describe the genetic explanation of OCD

Answer 1

Lewis (1936) studied his OCD patients and found that 37% had parents with OCD and 21% had siblings with OCD; suggests a genetic role in OCD

Diathesis-stress model: suggests that a genetic vulnerability to OCD is passed down but an environmental stress/experience is needed to trigger it.

Candidate genes have been identified e.g. 5HT1-D beta, which is involved in the efficiency of transporting serotonin (responsible for mood regulation) across synapses.

OCD is polygenic; Taylor (2013) analysed previous studies and found more than 230 potential candidate genes which are responsible for serotonin, dopamine and other mood regulating hormones

Question 2

Evaluate the genetic explanation of OCD

Answer 2

(+) Nestadt et al (2010) found concordance rates for OCD of 68% of MZ twins and 31% of DZ twins
(+) MZ>DZ which suggests some genetic influence
(-) conc(MZ) =/= 100% so not wholly genetic
(-) MZ twins share a more similar environment than DZ twins so could be due to environmental factors not genetic ones
(-) Because there are so many candidate genes, it gives little real life predictive value; not very useful

Question 3

Describe the neural explanation of OCD

Answer 3

Serotonin is a NT responsible for mood regulation i.e. carrying info about mood across synapses. Suggested that ppl with OCD have low levels of serotonin, which affects mood and other mental processes

There are neural correlates associated with OCD; patients tend to have abnormal functioning in the frontal lobe (responsible for decision making and logic) and the parahippocampal gyrus (responsible for processing unpleasant emotions)

Question 4

Evaluate the neural explanation of OCD

Answer 4

(+) Many drugs used to treat OCD increase the level of serotonin and seem to be very effective; suggests serotonin may be involved
(-) Treatment-causation fallacy; may not be CAUSED by serotonin at all
(+) Luo et al (2011) found that OCD patients had a smaller left parahippocamal gyrus than control ppts using structural MRI scanning; highly objective and controlled; good scientific credibility
(-) No cause and effect
(-) Lots of OCD patients have co-morbidity with depression; serotonin may be useful for depression but not necessarily for OCD

Question 5

Describe the biological approach to treating OCD

Answer 5

SSRIs (Selective Serotonin Re-uptake Inhibitors) prevent serotonin from being reabsorbed by the post synaptic neuron, which forces more serotonin to be made so post-synaptic neuron is more frequently stimulated and so fires more often; better mood regulation. This all works on the assumption the OCD is caused by a lack of serotonin.

Alternatives include tricyclics (which have the same effect on serotonin as SSRIs, but are an older type of drug with more side effects than SSRIs, so are a sort of last resort for ppl who don’t respond well to SSRIs) and SNRIs (serotonin-noradrenaline re-uptake inhibitors), which work not just on serotonin, but also on a NT called noradrenaline. These alternatives can be introduced after 3-4 months of SSRIs not working.

Drug therapy can also be combined with CBT if necessary, although in practice this only works for some.

Question 6

Describe the process of synaptic transmission with respect to serotonin

Answer 6

1) Electric impulse travels down neuron and reaches axon terminal button
2) Causes vesicles (containing serotonin) to move to the pre-synaptic membrane
3) Serotonin released into synaptic cleft and diffuses across to post-synaptic neuron
4) Serotonin binds to receptor sites on post-synaptic neuron
5) Post synaptic neuron fires
6) Serotonin travels back to pre-synaptic neuron where it’s broken down and re-used

Question 7

Evaluate the biological approach to treating OCD.

Answer 7

(+) Soomro et al (2009) found SSRIs to be consistently more effective than placebos in a meta analysis of 17 studies
(-) Goldacre (2013) criticised evidence for drug effectiveness, saying it was biased as a lot of the evidence is funded by the drug companies themselves and not all the evidence is reported
(+) Drugs are highly cost effective and require little effort from patient; saves time and money on NHS
(-) Drugs can have side effects, which put people off taking them and so decreases effectiveness