Biological explanation of OCD

2 neural explanations of OCD

abnormalities in worry circuits
abnormalities in neurotransmitters

3 areas of worry circuit

Orbitofrontal cortex
Basal ganglia
Thalamus

What is the orbitofrontal cortex role?

processes sensory info about possible danger, detects unseen dangers

What is the basal ganglia’s role?

filters dangers
stops repetitive safety behaviours once danger dealt with

What is thalamus’s role?

controls our response to danger

Explanation of worry circuit in OCD- exam style

Baxter(1992)
Basal ganglia does not properly suppress worries which triggers safety behaviours
messages continue to be sent even when dealt with worry
so impulse to act is not suppressed and behaviours become compulsive

Evidence for abnormalities in worry circuit

brain scans
Polak et al (2012)
symptoms can be reduced by altering activity through deep brain stimulation

Evaluation of worry circuit definition

-types of OCD such as order cannot be explained with this as it doesn’t involve threats
-brain scans are not consistent with every OCD
+surgery in these areas reduces symptoms

Which neurotransmitter is linked to OCD?

low serotonin

What is another word for repetitive thinking?

rumination

What drug increases the activity of serotonin?

SSRIs

Which neurotransmitter is linked to compulsive behaviour in OCD?

high dopamine

Evidence for neurotransmitter abnormalities

SSRIs are effective in reducing OCD symptoms
Soomro et al (2008)

Evaluation of abnormal neurotransmitters

-doesn’t mean serotonin causes OCD, drugs can be treating symptom not cause
-not all drugs are effective for OCD patients

What are the genes linked to OCD?

COMT and SERT

The COMT gene

production of enzyme which regulates dopamine
variation leads to high dopamine

The SERT gene

regulates transport mechanism for serotonin
variation leads to low serotonin

Twin studies

Evidence - Nestadt (2010)
problem is they assume twins raised in same environment

Evaluation of biological approach

-biological reductionism
-determinism as patients may feel that OCD is inevitable
-socially sensitive

Biological treatments for OCD

Prozac
9-12 weeks
reduces repetitive behaviour by ensuring OFC functions properly

Strengths of biological treatments

Soomro (2008)
cheap to patients
economic implications

Weaknesses of biological treatments

side effects like headache, nausea
more chance of relapse, but if combined with CBT could reduce relapse rates