The biological approach to explaining OCD

Question 1

A01 genetics

Answer 1

• Different, specific genes are inherited which are related to the onset of OCD
• COMT gene- involved in production of catechol-O-methyltransferase( COMT), which regulates the production of neurotransmitter dopamine that is implicated in OCD ( induces stereotyped movement resembling compulsive behaviours found in OCD patients)
  A specific allele which produces lower activity of the COMT gene and higher D levels is found more in ocd patients than non ocd patients
• SERT gene affects transport of serotonin creating lower levels, implicated in ocd
• Each of these genes create a diathesis for ocd and other disorders, other stressors affect what condition develops, these genes arent the sole factor for ocd

Question 2

AO1 neural-

Answer 2

Genetic factors may affect certain brain circuits and levels of neurotransmitters that are abnormal
- Dopamine levels are high in people with ocd, based on animal studies- high doses of drugs that enhance the amount of dopamine induce stereotyped movements resembling compulsive behaviours found in ocd patients ( szechtman 1998)
- Serotonin low levels are associated with ocd, based on the fact that antidepressant drugs which inc serotonin levels are shown to reduce ocd symptoms, however drugs which dont effect serotonin levels dont ease symptoms of ocd ( jenicke 1992)
Abnormal brain circuits-
Caudate nucleus which usually supresess signals from OFC, can damage causing minor worries to not be supressed causing thalamus to alert , which in turn sends signals back to the OFC causing a worry circuit
Supported by pet scans showing people with active ocd symptoms have high levels of activity in the OFC
When you have an impulse (e.g. to wash your hands when they are dirty), the orbital frontal cortex translates that impulse into action (e.g. washing your hands), and performing that action reduces the impulse. However, with OCD sufferers, it may be that the overactivity of the orbital frontal cortex means these impulses continue even after performing the behaviour, becoming obsessions and compulsions.

Question 3

Evidence- study of genetic basis of OCD

Answer 3

• Nestadt et al ( 2000)
• Got 80 patients with OCD and 343 of their first degree relatives to compare with 73 patients and 300 of their relatives
• Found that people with a first degree relative with OCD had a 5 times greater risk of having OCD at a point in their lives compared with general population
  A meta analysis of 14 twin studies proved that monozygotic twins were more than twice as likely to develop OCD if their other twin had it than dizygotic twins ( billett et al)

Question 4

A03- Research support for genes and OFC

Answer 4

Menzies et al (2007) used mri to produce images of brain activity in ocd patients and close family members without ocd, and a control group
OCD patients and close relatives had inc grey matter in ofc
- Supports the idea that anatomical differences are inherited and lead to ocd in certain individuals

Question 5

Real world application AO3

Answer 5

Mapping of the human genome has led to the hope that specific genes could be linked to specific mental disorders
- One of the parents to be may have the COMT gene, mothers fertilised eggs can be screened to give a choice of aborting eggs with the gene
-Gene therapy allows turning genes off so a disorder is not expressed
- Displays a clear relationship between specific genes and ocd disorder, this correlation is being displayed in real life showing significance

Question 6

Alternative explanations of OCD AO3