OCD

• Obsessive compulsive disorder


  A condition, type of anxiety disorder characterised by obsessions and/or compulsive behaviour
• Obsessions


  A cognition (takes place in the mind), recurring thoughts
• Compulsions


  A behaviour (an action/ something you do), repetitive behaviour
• Behavioural characteristics of OCD

  • Repetitive compulsions
  • Avoidance
• Biological explanation for OCD

  • OCD is characterised by obsessions or compulsions and this causes anxiety so avoidance behaviour occurs which tend to be irrational to an outsider
• Emotional characteristics of OCD

  • Anxiety and distress
  • Accompanying depression
  • Guilt and disgust
• Cognitive characteristics of OCD

  • Obsessive thoughts
  • Self-awareness of irrationality
• Genes

  Make up chromosomes and consist of DNA which codes the physical features of an organism (such as eye colour, height) and psychological features (such as mental disorder, intelligence)
• Transmission

  Genes are transmitted from parents to offspring, i.e., inherited
• Neural explanations

  The view that physical and psychological characteristics are determined by the behaviour of the nervous system, in particular the brain as well as individual neurons
• The biological approach

  Views OCD as a physical illness and emphasises the importance of the physical processes in the body like genetic inheritance and neural function
• Genetic explanation

  OCD is genetically inherited from the parents via genes. OCD runs in families and so have genetic vulnerability
• Lewis (1936)


  • 37% of his OCD patients had parents with OCD
  • 21% had siblings with OCD
• SERT(5-HTT) - Serotonin Transporter

  • Gene involved in regulation and transportation of serotonin usage and regulates anxiety
  • Mutated gene affects the efficiency of serotonin transportation across synapses, resulting in reduced serotonin levels in the synapses as more is reabsorbed by the neurone, leading to low levels of serotonin and can cause anxiety which drives the anxious obsessional thoughts in OCD patients
• COMT gene


  • Breaks down dopamine in the synapse, involved in brain activities e.g. emotional responses
  • A mutated gene lowers production of the enzyme so high levels of dopamine are present, causing compulsive behaviour
• OCD is polygenic (several genes) and aetiologically heterogenous so origin has many causes
• Taylor - 230 genes involved
• Genes impacting neural correlates

  Genes associated with OCD are likely to affect the levels of key neurotransmitters and brain structures
• Serotonin and neurotransmitters


  • Low levels of serotonin so normal transmission of mood-relevant information does not take place so mood is affected
  • Decrease in serotonin (mood affected), increase in dopamine (compulsive behaviour)
• Abnormal brain circuits


  • Orbital frontal cortex (OFC) is overactive, transmits warning of worries to thalamus, results in compulsions
  • Caudate nucleus not functioning properly so doesn't surpress the worries in OFC
  • Basal ganglia hypersensitivity linked to repetitive actions
  • Parahippocampal gyrus abnormal processing of unpleasant emotions
  • Lateral lobes impaired thinking and hoarding
• Decision-making system


  The control of thinking/ decision making can become impaired
• Genetic explanation eval - Good supporting evidence

  • Evidence to support the idea of vulnerability to OCD due to genes. The “twin studies” Nestadt et al (2010) reviewed previous twin studies and found that 68% of identical twins shared OCD as opposed to 31% of non- identical twins. This suggests that there is a genetic influence on OCD.
• Genetic explanation eval - Too many candidate genes

  • The twin studies suggest that OCD is largely under genetic control, but as OCD is polygenic haven’t figured out all the genes involved. The genetic explanation provides little predictive value so is ultimately useless as it is hard to pinpoint the exact genes involved.
• Genetic explanation eval - Environmental risk factors

  • OCD can’t be entirely genetic in origin - Cromer et al (2007) found over half OCD patients suffered a traumatic experience in their past. -
  • Environmental factors can trigger or increase the risk of developing OCD suggested by the Diathesis stress model. Identical twins have a higher concordance rate for OCD than non-identical twins, but the rate is still less than 100%.
• Neural explanation eval - Supporting evidence

  • Antidepressants work purely on serotonin system, increasing levels of this neurotransmitter. Such drugs are effective in reducing OCD symptoms so serotonin system must be involved in OCD.
• Neural explanation eval - Brain scans

  • Brain scans of patients that suffer from OCD show heightened activity in the orbitofrontal cortex. This happens if the scans are taken while their OCD is active. This suggests that obsessional thinking could be caused by damaged brain circuits.
• Neural explanation eval - Unclear neural mechanisms

  • Studies of decision-making show that neural systems are the same systems that function abnormally in OCD (Cavedini et al 2002).  Research has identified other brain systems involved sometimes but fails to find a system that is always involved in OCD. Therefore, we can’t claim to understand neural mechanisms involved in OCD.
• Neural explanation eval - Chicken or egg?

  • Evidence to suggest various neurotransmitters and structures don’t function normally in OCD patients. This is not the same as saying that this abnormal functioning causes OCD. These biological abnormalities could be a result of OCD rather than it’s cause.
• Neural explanation eval - Co-morbidity

  • Some OCD patients also develop depression. Depression can cause disruptions to the serotonin system. Therefore, it could simply be that the serotonin system is disrupted in many patients with OCD because they are depressed as well.
• Genetic explanation evals

  • Good supporting evidence - Nestadt
  • Too many candidate genes
  • Environmental risk factors - cromer
• Neural explanation evals

  • Supporting evidence
  • Brain scans
  • Unclear neural mechanisms - Cavedini
  • Chicken or egg?
  • Co-morbidity
• Drug therapies


  Aims to increase levels of neurotransmitters in the brain to increase activity
• Treatment for OCD


  Aims to increase the levels of serotonin
• SSRIs (Selective serotonin reuptake inhibitors)


  Anti-depressant drug used to tackle the symptoms of OCD
• How SSRIs work


  1. Prevent the break down and reabsorption of serotonin

  2. Increases the levels of serotonin in the synapse

  3. Stimulates postsynaptic neuron
• Combining SSRIs and other treatment

  Drugs used alongside Cognitive behaviour therapy (CBT) to treat OCD
• How drugs and CBT work together

  • Drugs reduce the patient's emotional symptoms
  • Allows them to engage more effectively with CBT
• Alternatives to SSRIs


  • Increase dosage of SSRIs
  • Combine SSRIs with another drug
  • TRICYLICS (older antidepressant with severe side-effects)
  • SNRIS (Serotonin and noradrenaline reuptake inhibitors)
  • ANTI-ANXIETY DRUGS
• SNRIS (Serotonin and noradrenaline reuptake inhibitors)

  A class of antidepressant drugs that increase the levels of serotonin and another neurotransmitter (noradrenaline)
• ANTI-ANXIETY DRUGS


  • Increases the levels of inhibitory neurotransmitter (gamma-aminobutyric acid)
  • Slows down neural activity
  • Helps reduce anxiety in OCD patients
  • Reduces obsessive thoughts/compulsive behaviour