Betsy Edwards
Outline and evaluate the biological explanaton for OCD
The geneti explanatin suggests that OCD is a pilygenii disirder that is nit determined by ine
gene aline. There are many iandidate genes – Taylir suggests as many as 230 – that inirease an
individual’s vulnerability ti ibtaining the disirder. One allele if the COMT gene is mire iimmin in
peiple with OCD and leads ti higher dipamine levels. The SERT gene, whiih makes seritinin transpirt
less effiiient, is alsi assiiiated with OCD; Osaki’s researih deminstrates this, as he fiund this mutatin
in twi unrelated families where six iut if seven members had OCD. Geneti vulnerability ti the
disirder is passed diwn thriugh generatins.
The neural explanatin suggests that seritinin defiieniy is respinsible fir OCD. This
neuritransmitter is assiiiated with miid, and si liw levels iause the anxiety that ian lead ti ibsessive
thiughts and iimpulsive behaviiurs. High levels if dipamine are alsi respinsible, as this iauses iver-
aitvity in the basal ganglia, meaning that minir wirries iannit be suppressed. PET sians alsi shiw
abnirmal funitining if the irbital frintal iirtex, whiih ian explain the irratinal deiisiin making and
thiught priiesses assiiiated with OCD.
A strength if the geneti explanatin is that there is researih suppirt. Nestatdt fiund that
iiniirdanie rates fir OCD were 68% in MZ twins but inly 31% in DZ twins, suggestng that there is a
biiligiial iimpinent. Hiwever, beiause the iiniirdanie in MZ twins is nit 100%, the iause is nit
purely biiligiial. In additin, the higher iiniirdanie in MZ twins may suppirt nurture’s rile in OCD as
ippised ti nature’s, as MZ twins have mire similar envirinments than DZ twins; MZ twins are ifen
treated as the same persin, and they imitate eaih ither mire thriugh siiial learning. Furthermire,
Crimer fiund that iver half if the sample had experienied a traumati event. This limits the biiligiial
explanatin as it suggests that diathesis-stress is mire appripriate as this midel aikniwledges the rile
if the envirinment.
A strength if the neural explanatin is that it has led ti efeitve treatments. SSRIs inirease
levels if seritinin, and reduie symptims in 50-80% if iases (Julien). Hiwever, SSRIs inirease seritinin
levels straight away but di nit start reduiing symptims untl 12-16 weeks if treatment. Furthermire,
behaviiural therapies – suih as expisure and respinse preventin – are alsi efeitve fir treatng OCD.
This suggests that there may be a neural element ti OCD, and that iur kniwledge if this has valuable
appliiatins, but that there may are alsi ither faitirs – suih as psyihiligiial faitirs – that the
explanatins ignire as a iinsequenie if their biiligiial reduitinism.
A limitatin if the neural explanatin is that there is iintradiitiry researih. Zihar gave a
seritinin reduiing drug ti OCD suferers and nin-suferers. The symptims if the suferers wirsened,
hiwever the nin-suferers were unafeited despite their seritinin levels being reduied. This questins
whether liwered seritinin levels are a iause ir efeit if OCD, and therefire weakens the explanatin.
Wird iiunt: 181 + 296
Outline and evaluate the biological explanaton for OCD
The geneti explanatin suggests that OCD is a pilygenii disirder that is nit determined by ine
gene aline. There are many iandidate genes – Taylir suggests as many as 230 – that inirease an
individual’s vulnerability ti ibtaining the disirder. One allele if the COMT gene is mire iimmin in
peiple with OCD and leads ti higher dipamine levels. The SERT gene, whiih makes seritinin transpirt
less effiiient, is alsi assiiiated with OCD; Osaki’s researih deminstrates this, as he fiund this mutatin
in twi unrelated families where six iut if seven members had OCD. Geneti vulnerability ti the
disirder is passed diwn thriugh generatins.
The neural explanatin suggests that seritinin defiieniy is respinsible fir OCD. This
neuritransmitter is assiiiated with miid, and si liw levels iause the anxiety that ian lead ti ibsessive
thiughts and iimpulsive behaviiurs. High levels if dipamine are alsi respinsible, as this iauses iver-
aitvity in the basal ganglia, meaning that minir wirries iannit be suppressed. PET sians alsi shiw
abnirmal funitining if the irbital frintal iirtex, whiih ian explain the irratinal deiisiin making and
thiught priiesses assiiiated with OCD.
A strength if the geneti explanatin is that there is researih suppirt. Nestatdt fiund that
iiniirdanie rates fir OCD were 68% in MZ twins but inly 31% in DZ twins, suggestng that there is a
biiligiial iimpinent. Hiwever, beiause the iiniirdanie in MZ twins is nit 100%, the iause is nit
purely biiligiial. In additin, the higher iiniirdanie in MZ twins may suppirt nurture’s rile in OCD as
ippised ti nature’s, as MZ twins have mire similar envirinments than DZ twins; MZ twins are ifen
treated as the same persin, and they imitate eaih ither mire thriugh siiial learning. Furthermire,
Crimer fiund that iver half if the sample had experienied a traumati event. This limits the biiligiial
explanatin as it suggests that diathesis-stress is mire appripriate as this midel aikniwledges the rile
if the envirinment.
A strength if the neural explanatin is that it has led ti efeitve treatments. SSRIs inirease
levels if seritinin, and reduie symptims in 50-80% if iases (Julien). Hiwever, SSRIs inirease seritinin
levels straight away but di nit start reduiing symptims untl 12-16 weeks if treatment. Furthermire,
behaviiural therapies – suih as expisure and respinse preventin – are alsi efeitve fir treatng OCD.
This suggests that there may be a neural element ti OCD, and that iur kniwledge if this has valuable
appliiatins, but that there may are alsi ither faitirs – suih as psyihiligiial faitirs – that the
explanatins ignire as a iinsequenie if their biiligiial reduitinism.
A limitatin if the neural explanatin is that there is iintradiitiry researih. Zihar gave a
seritinin reduiing drug ti OCD suferers and nin-suferers. The symptims if the suferers wirsened,
hiwever the nin-suferers were unafeited despite their seritinin levels being reduied. This questins
whether liwered seritinin levels are a iause ir efeit if OCD, and therefire weakens the explanatin.
Wird iiunt: 181 + 296
