biological approach to explain OCD

what is OCD

recurrent and persistent thoughts, urges or images that are intrusive and cause disturbance

cause anxiety and stress

what are obsessions

intrusive and involuntary thoughts

e.g. germs and contamination

what are compulsions

repetitive behaviours to alleviate the distress caused by obsessions

e.g. compulsive washing

what is OCD classified as

anxiety disorder

behaviour characteristics

compulsive behaviour

emotional characteristics

anxiety

depression

cognitive characteristics

obsessive thoughts

using cognitive strategies

insight

DSM-5 categories of OCD

OCD - obsession and/or compulsion

trichotillomania - compulsive hair pulling

hoarding disorder - compulsive gathering possessions and inability to part with anything regardless of value

excoriation disorder - compulsive skin picking

OCD cycle

1. obsessive thought

2. anxiety

3. compulsive behaviour

4. temporary relief

example of behaviour symptoms

washing hands

example of emotional symptoms

anxiety

example of cognitive symptoms

recurring thoughts of disease and images of dirt

what does the genetic explanation suggest

whether a person develops OCD is at least partly due to genetics

explains why patients often have family with OCD

what are candidate genes

isolated genes assumed to be the cause of a condition

possible candidate genes for OCD

SERT gene - regulating serotonin (message transfer across synapses)

COMT gene - regulates dopamine (motivation and drive)

what does a variation of SERT cause

lower levels of serotonin

incorrect messaging across synapses

what does a variation of COMT cause

higher levels of dopamine

causes compulsive behaviours

what is polygenic

a condition is caused by a group of genes

who supports polygenic assumption for OCD

taylor (2003) - 230 candidate genes may be involved and different genetic variations contribute to different OCD types

can individuals be affected by different gene groups

yes - aetiologically heterogeneous (origins vary from one person to another)

how can neurotransmitters/chemicals cause OCD

when the levels become too high/low

what is the basal ganglia

controls movement and other functions e.g. learning and emotional processing

how does the basal ganglia affect OCD

patients that suffer head injuries in this region often develop OCD-like symptoms

what is the thalamus

processes movement and sensory information (except smell) and sends it elsewhere for interpretation

has a role in sleep, wakefulness, learning and memory

how does the thalamus affect OCD

increased motivation to clean/check for safety

overactive thalamus = overactive OFC

what is the orbitofrontal cortex (OFC)

involved in emotion, reward value and reward-related decision-making

how does the OFC affect OCD

PET scans found higher activity in patients with OCD when told to go against their obsessions

overactive OFC = increased anxiety and planning to avoid anxiety

what does the diathesis-stress model suggest

people gain OCD vulnerability through genes but environmental stressors are also required e.g. stressful events

genetic research support (strength 1)

research support - lewis (1936) 37% patients also had parents with OCD and 21% with suffering siblings

genetic twin studies (strength 2)

billett et al (1998) MZ twins had x2 risk of developing OCD than DZ twins if one had OCD

nastadt et al (2010) 68% MZ twins developed OCD compared to 31% DZ twins

increases theory validity

genetic limitations

inconsistent findings - other areas of the brain have been involved, no consistent brain system that plays a role

alternative explanations - not 100% concordance rate in twin studies so other factors must be considered (diathesis-stress model)

polygenic - not everyone is the same

ethical issues

brain strengths

family studies - person with an OCD family member is 4x more likely to develop it (marini and stebnicki 2012)

drug therapy - antidepressants e.g. SSRIs are effective in reducing symptoms, increases validity and reliability

brain limitations

drug therapy - not completely effective, cannot guarantee serotonin levels was the cause of OCD

biological reductionism - ignores environmental roles, twins grow up in the same environment so they are likely to respond to upbringing etc