An anxiety disorder characterised by obsessions and compulsions
Symptoms of OCD
Obsessions
Compulsions
Biological explanations for OCD
Genes
Neurochemistry
Neural functioning
Genetic explanation
OCD is inherited (passed on through genes) from generation to generation
People inherit a candidate gene which creates a vulnerability to OCD but a life stressor is needed to trigger it
COMT
Candidate gene managing the production of dopamine (increase)
SERT
Candidate gene for transportation of serotonin (decrease)
Diathesis stress model
Genes such as COMT and SERT only create a vulnerability (risk of developing) for OCD
Other factors (stressors) need to be present to trigger the development of the disorder
Neurochemistry explanation
OCD is caused by abnormal levels of specific neurotransmitters
Neural functioning explanation
Several areas of the frontal lobe are abnormal in people with OCD
The Orbitofrontal cortex (OFC) is the brain's 'worry detector'
The caudate nucleus suppresses signals from the OFC reaching the thalamus
When the caudate nucleus is damaged it cannot suppress minor 'worry' signals which causes the thalamus to be alerted
Supporting research
Point - supporting research from family and twin studies for genetic causes of OCD
Evidence - Nestadtet al. (2010) reviewed previoustwin studies and found that 68% of identical twins shared OCD as opposed to 31% of non-identical twins.
Explain - suggests that the cause of OCD is partlygenetic.
Link - increase the validity of genetic explanations of OCD.
Research support for the diathesis-stress model
Point - supporting research evidence that environmental factors may also trigger or increase risk of developing OCD.
Evidence - Cromeret al. found that over half the OCD patients in their sample had a traumatic event in their past and that OCD was more severe in those with more than one trauma.
Explain - This suggests that OCD may be best explained as the result of environmental causes.
Research support for genes and OFC
Point - One strength of neural explanations of OCD is that there is supporting evidence of the genetic link to abnormal levels of neurotransmitters.
Evidence - Menzies et al used MRI to produce images of brain activity in OCD patients and their familywithout OCD and a control group of unrelatedhealthy patients. OCD patients and their close relatives had reducedgrey matter in key regions of the brain, including the OFC.
Explain - suggests that anatomical differences are inherited and these may lead to OCD in certain individuals.