Bio-Explaining OCD

• OCD is a mental disorder characterised by anxiety and irrational thnking
• Behavioural characteristics:

  • Compulsions are repetitive (compelled to wash your hands)
  • Compulsions reduce anxiety produced by obsessions (response to obsessive fear of germs)
  • Avoidance - situations that trigger anxiety (emptying bin)
• Emotional characteristics:

  • Anxiety/distress - OCD particularly unpleasant because of powerful anxiety produced by obsessions/compulsions
  • Accompanying depression - low mood/lack of enjoyment in activities
  • Guilt and disgust - directed at dirt or self
• Cognitive characteristics:

  • Obsessive thoughts - about 90% - reoccurring obsessive thoughts
  • Cognitive strategies to deal with obsessions (praying/meditating) to lessen anxiety
  • Insight to excessive anxiety - aware that behaviour isn't rational but still experience catastrophic thoughts about worst case scenarios - also ten to be hypervigilant
• (GE) - Genes appear to be involved in individual vulnerability to OCD. Lewis noticed that of his 50% OCD patients, 37% had parents with OCD and 21% had siblings with OCD. This suggests that OCD may run in families, passing on vulnerability of the disorder.
• The diathesis stress-model suggests that certain genes leave people more likely to suffer a mental disorder, but then an environmental experience (stress) may trigger the cost.
• Candidate genes are genes which create vulnerability.
• The candidate gene 5HTI-Dbeta is implicated in the efficiency of transport across the synapses.
• The candidate gene SERT (SERotonin Transporter) effects transport of serotonin causing lower levels of serotonin which is also associated with OCD.
• The candidate gene COMT is associated with the regulation of the neurotransmitter dopamine, resulting in higher levels of dopamine and this variation is more common in patients with OCD, in comparison to ppl without OCD.
• OCD is polygenetic (many genes involved rather than just a single one. Taylor analysed findings of previous studies and found evidence that up to 230 genes may be involved in OCD.
• S of genetic explanation

  • Good supporting evidence - twin studies provide strong evidence. Neustadt et al reviewed prev twin studies and found that 68% of identical twins shared OCD compared to 31% of non-identical twins. Fam studies have found that a person with a fam member diagnosed with OCD is around 4 times more likely to develop as someone without.
• W of genetic explanation:

  • There are too many candidate genes too identify and each genetic variation only increases risk of OCD by a fraction. As a consequence, genetic explanations aren't very useful as they provide little predictive value.
  • Cromer et al found that half his sample of OCD patients had a traumatic evet in their past, with more severe OCD in those with more than one trauma. Therefore, OCD cannot be entirely genetic, suggesting behaviourist approach provides a better explanation in how OCD arises.
• (NE) - Rauch et al used PET scans to study brain activity of OCD sufferers when faced with objects of their obsessions and compulsions and found increased activity in frontal lobes and basal ganglia was found executing a skill pattern.
• (NE) - The basal ganglia is made up of a series of interconnected brain structures and plays a role in cognition, attention and movment.
• The basal ganglia are involved in the formation of habits so dysfunction in this area could lead to problems with initiation and control of repetitive/ habitual behaviours. Saxena et al suggest that together, many basal ganglia structures form a 'control system' that regulates cortical striatal thalamic circuit which is a loop of neurons connecting prefrontal cortex, basal ganglia and thalamus.
• A failure in basal ganglia control system means that habitual and routine-like motor responses originating in the CST circuit may not be inhibited, leading to uncontrollable compulsive habits.
• Max et al found that when the basal ganglia is disconnected from the frontal cortex during surgery, OCD-like symptoms are reduced, providing further support for the role of basal ganglia in OCD.
• The frontal lobes are responsible for logical thinking and making.
• Left Para hippocampal gyrus associated with processing unpleasant emotions, functioning abnormally in OCD.
• Serotonin is a neurotransmitter which regulates mood.
• Neurotransmitters relay info from one neuron to another. If someone has low levels of serotonin the normal transmissions of mood relevant info does not occur and so mood/other mental processes may be infected.
• OCD is commonly comorbid with depression and when patients given SSRI'S for depression, occasionally OCD symptoms also ease. However, raised levels of serotonin can make OCD symptoms worse (Hollander et al). Researchers conducted that OCD is related to abnormality in neurotransmitter systems linked to the serotonin system.
• S of neural explanation:

  • McGuire et al showed OCD sufferers images of their obsessions and found increased activity in PET scans in the CST circuit, showing these structures do have some influence n OCD
  • Supporting evidence
• W of Neural explanations:

  • Not clear exactly what neural mechanisms are involved as research has also identified other brain systems that may be involved sometimes but no system has always been found that always plays a role in OCD. Therefore, we don't really understand the neural mechanisms involved.
  • Evidence to suggest various neurotransmitters and structures of the brain do not function normally in patients with OCD but this doesn't necessarily mean they caused OCD, they could be the result of OCD.