Biological apprach in explaining OCD

What are the 2 explanations of OCD

Genetic and neural

Genetic explanation of OCD

• Suggests OCD is inherited and person at risk of developing OCD due to their genetic makeup.

• Diathesis stress model says certain genes make people more likely to suffer OCD and some environment,a stress needed to trigger OCD

• OCD is polygenic (not caused by single gene)- Genes involved in OCD associated with dopamine and serotonin

2 genes associated with OCD- Genetic explanation

• COMT gene produces an enzyme, regulates neurotransmitter dopamine.

• Causes higher levels of dopamine which is more common in people with OCD

• SERT gene linked to serotonin and affects the transportation of it.

• Causes lower levels of serotonin which is associated with OCD.

Strength of the genetic explanation- Research support

• Evidence people are vulnerable to OCD due to genetic makeup.

• Nestadt et al reviewed twin studies- found 68% monozygotic (identical) twins shared OCD compared to 31% of dizygotic.

• Evidence from family studies- person with family member diagnosed with OCD 4x more likely to develop it

• Shows the genetic influence on development of OCD

Weakness of genetic explanation- Environment risk factors

• Evidence that genetic variation makes a person more/less vulnerable to OCD but OCD isn’t entirely genetic in origin- environmental risk factors increase risk of developing OCD

• Cromer et al found ½ of OCD patients had traumatic event in their life

• OCD also more severe in ppl with more than 1 trauma.

• Means genetic vulnerability only provides partial explanation for OCD

Diathesis- stress model affecting OCD

Unlikely one gene is solely responsible for OCD- too complex

• Genes produce a vulnerability

• Then certain environmental stressors triggers OCD in those with the specific genes

Neural explanation of OCD- Neurotransmitters

• Serotonin regulated mood- low levels associated with mood disorders like OCD.

• Found drugs that increase S are effective in treating OCD.

• High dopamine associated with OCD especially compulsive behaviour.

Neural explanation for OCD- Brain structure (OFC)

Different regions in brain associated with OCD

• Orbitofrontal cortex converts worrying info into thoughts and actions. 

• PET scans showed higher activity in OFC in patients with OCD while symptoms are active e.g. person with germ obsession holding dirty cloth.

• High activity in OFC increases converting info into actions- causes compulsions, prevents person from stopping behaviour.
  

Neural explanation for OCD- Brain structure (Basal Ganglia)

• Involved in multiple processes like coordination of movement- Damage to Basal causes OCD symptoms.

• Found when Basal disconnected from frontal cortex during surgery, OCD symptoms reduced- supports that its involved.

Strength of neural explanation- Research support

• Antidepressants only increasing serotonin effective in reducing OCD symptoms- shows its involved in OCD.

• Symptoms linked to other condition like Parkinson disease- has a biological basis.

• If biological disorder produced OCD symptoms- assume biological explanation valid in explaining OCD

  Suggests biological factors responsible for OCD

Weakness- Alternative explanation

2 process model can be applied to OCD.

• Learning anxiety inducing stimulus can occur through classical conditioning, e.g. dirt (germs) paired with anxiety (becoming ill).

• Compulsive behaviour (handwashing) then maintained through operant conditioning & negative reinforcement- compulsive behaviour reduces the anxiety.

• Supported by success of behavioural treatments for OCD- 60-90% symptoms of patients improved.