Biological approach

• Genetic explanation of OCD

  Suggests OCD may be inherited, as gene markers predict its presence
• Genes associated with OCD

  • Gene 9
  • COMT
  • SERT
  • Up to 230 separate genes may be involved, making OCD polygenic
  • OCD is aetiologically heterogeneous as different gene combinations could lead to it
• COMT gene

  Associated with regulation of neurotransmitter dopamine, one variation results in higher dopamine levels and is more common in OCD patients
• SERT gene

  Linked to neurotransmitter serotonin, affects serotonin transport and is associated with lower serotonin levels in OCD
• 37% of OCD patients had parents with the disorder and 21% had siblings who suffered
• Research from family studies provides support for a genetic explanation of OCD, but does not rule out environmental factors
• Neural explanations of OCD

  Focus on neurotransmitters and brain structures in OCD development
• Role of serotonin

  Regulates mood, lower levels associated with mood disorders like depression, may prevent repetition of tasks
• Role of dopamine

  Higher levels associated with compulsive behaviours in OCD
• Brain regions implicated in OCD

  • Basal ganglia - involved in movement coordination, disconnection from frontal cortex reduces OCD symptoms
  • Orbitofrontal cortex - converts sensory info to thoughts/actions, heightened activity increases compulsions
  • Parahippocampal gyrus - regulates unpleasant emotions
• No twin study has found 100% concordance rate in identical twins, meaning biological factors are not the only cause of OCD
• Drugs that work on serotonin system cover up symptoms but don't treat root cause of OCD
• Antidepressant drugs (SSRIs)


  Increase serotonin availability in synapses by preventing reuptake, improve mood and reduce anxiety in OCD
• Anti-anxiety drugs (Benzodiazepines)

  Enhance action of neurotransmitter GABA, which tells neurons to 'slow down', reducing anxiety in OCD
• Biological treatments like antidepressants and anti-anxiety drugs are more cost-effective than psychological treatments like CBT
• Drugs can be more successful than psychological treatments for unmotivated patients
• Drug treatments have potential side effects like addiction, aggression, memory impairment
• Drug treatments only treat symptoms, not underlying cause, leading to high relapse rates compared to psychological treatments