Explaining OCD

• What is the biological approach to OCD?

  - explains mental health conditions like OCD as being due to faulty physical processes

  - this explanation includes the physical structure of your DNA, inherited from your parents

  - DNA codes for other aspects of your biology, such as how neurotransmitters are processed in the synapse and the development and functioning of larger structures e.g. brain regions
• What is OCD?

  - obsessive compulsive disorder

  - affects approximately 1 in 50 people

  - symptoms include obsessive thoughts and compulsive behaviours

  - obsessive thoughts are repetitive, distressing mental images or concerns that provoke anxiety

  - compulsions are actions that individuals feel they need to perform to reduce the discomfort caused by these thoughts

  - unfortunately, the relief is only temporary as obsessive thoughts quickly return
• What are the common obsessions (repetitive thoughts) and compulsions (repetitive behaviours) associated with OCD?

  - thoughts surrounding contamination/ infection leads to repetitive cleaning of hands/surfaces

  - thoughts surrounding burglary/theft leads to repeatedly checking doors are locked

  - thoughts surrounding (electrical) fires leads to repeatedly checking power switches are off
• What is the genetic explanation to OCD?

  - there is no singular OCD gene, however it is thought a vulnerability or predisposition to OCD is inherited from parents

  - genetic analysis has revealed around 230 separate 'candidate genes' found more frequently in people with OCD

  - many candidate genes influence the functioning of neural systems in the brain e.g. the SERT gene affects re uptake in the serotonin system

  - other identified genes include gene 9, COMT gene and 5HT1-D beta gene

  - as so many candidate genes have been identified, this suggests OCD is poly genetic, meaning a predisposition to OCD requires a range of genetic changes

  - OCD is also known as aetiologically heterogeneous - different genes may be involved in OCD in different people and different types of OCD
• STRENGTH of the biological approach to explaining OCD: evidence for the heritage of OCD comes from family and twin studies

  EVIDENCE - the prevalence rate of OCD in the general population is 2%, however if an individual has OCD, the likelihood that their first degree relatives have OCD (concordance rate) rises to 10%

  EXP - this increased risk is arguably due to shared genetics, with first degree relatives sharing 50% of their genes. Identical (monozygotic) twins (who share 100% of their genetics) have a 68% concordance rate for OCD, while non-identical (dizygotic) twins have a 31% concordance rate

  EVAL - the presence of genes isn't the whole story because these genes have functions (coding for aspects of your biology) and it's thought that candidate genes might influence the functioning of neural systems in the brain, especially the serotonin system
• What is the neural explanation for OCD?

  - includes biochemical causes (an imbalance of neurotransmitters - chemicals that communicate information between neurons) and the large neural structures in the brain that are made up of many neurons (OFC, caudate nucleus and thalamus)

  - serotonin is the neurotransmitter most associated with OCD as lower levels are usually found in people with OCD, which is associated with high levels of anxiety

  - low serotonin levels are thought to cause obsessive thoughts and the low level is likely due to it being removed too quickly from the synapse before it has been able to transmit its signal/ influence the postsynaptic cell

  - high levels of dopamine are also found in OCD sufferers. Dopamine is linked to attention and therefore high levels of it is associated with over-focussing on obsessive thoughts and repetitive behaviours
• What is the process of synaptic transmission and how does this differ in people with OCD?

  - serotonin and other neurotransmitters are chemical messengers

  - presynaptic neurons releasers neurotransmitters which are detected by receptors on the post synaptic neuron

  - if the signal is strong enough then the message is passed on

  - the neurotransmitters detach from the receptors and are taken back to the presynaptic neuron through a process called reputake

  - it seems this process happens too quickly in people with OCD, leading to reduced serotonin levels in the synapse
• What are the neural structures in the brain that explain OCD?

  - the 'worry circuit' is a set of brain structures including the orbitofrontal cortex (OFC) - responsible for rational decision making - the basal ganglia system (especially the caudate nucleus) and the thalamus

  - communication between these structures in the worry circuit appears to be overactive in people with OCD, leading to an inability to filter out small worries

  - in normal functioning, the basal ganglia filter out minor worries coming from the OFC, but if this area is hyperactive, even small worries get to the thalamus, which is then passed back to the OFC, forming a loop (which are the recurring obsessive thoughts)

  - this abnormal activity is ultimately responsible for the repetitive motor functions (compulsions)

  - these are an attempt to break this loop - while carrying out the compulsion may give temporary relief, the hyperactive basal ganglia will soon resume the worry circuit
• What is the Parahippocampal Gyrus?

  - a brain area linked to OCD, an area of correct close to the hippocampus on the brain's underside

  - it is responsible for regulating and processing unpleasant emotions and has been seen to function abnormally in cases of OCD
• STRENGTH of the Biological Approach to explaining OCD: evidence to suggest there is a genetic origin to OCD

  EVIDENCE - Nestadt (2010) shows there is a high concordance rate between close family members for OCD

  EXP - non-identical twins have a 31% concordance rate and identical twins have 68%. MZ and DZ twins grow up sharing similar environments like food, upbringing and education, and life events like bereavement or parental divorce

  EVAL - this suggests that the additional shared DNA is responsible for the increased concordance
• WEAKNESS of the Biological Approach to explaining OCD: there are issues with assuming it is DNA that results in the high concordance rates for family members

  EVIDENCE - the correlation in family and twin studies does not automatically equal causation

  EXP - it may not be the shared genetics behind the high concordance rates - closer family members also share similar environments. Identical monozygotic twins may be treated more similarly because they look alike compared to non-identical (dizygotic) twins

  EVAL - as the concordance rate for MZ is 68%, not 100%, the level we would expect for an entirely genetically determined psychological feature, there must be some role for the environment
• WEAKNESS of the Biological Approach to explaining OCD: the diathesis-stress model may be a more valid explanation than biological processes alone

  EVIDENCE - individuals inherit a genetic vulnerability to OCD (diathesis), however the disorder does not develop unless there is an environmental factor (stressor), such as a traumatic life event

  EXP - Cromer showed 54% of 265 patients with OCD reported at least one traumatic life event, and those with traumatic life events reported increased severity of OCD symptoms

  EVAL - this demonstrates an environmental aspect to OCD
• STRENGTH of the Biological Approach to explaining OCD: supported by scientific methods

  EVIDENCE - several neuroimaging studies using PET scanners have shown hyperactivity in the OFC and the caudate nucleus in people with OCD, both while scanning the brain at rest and when symptoms are stimulated

  EXP - however there is a problem with this neural evidence as it is only correlational

  EVAL - researchers cannot be sure if the hyperactivity in these areas is the cause of OCD or a consequence of having OCD
• WEAKNESS of the Biological Approach to explaining OCD: effectiveness of drug therapies

  EVIDENCE - a meta-analysis by Soomro demonstrated SSRIs are more effective than placebos, suggesting there is a biological aspect to OCD

  EXP - however, despite altering levels of serotonin in the synapse within hours, these drugs take weeks to reduce symptoms, and 40-60% of patients show no or partial symptom improvement

  EVAL - these findings suggest low levels of serotonin have a role to play in OCD but are not the sole cause of OCD
• How might the SERT gene cause OCD?

  • affects the transportation of serotonin
  • OCD may be caused by a mutation of this gene
  • the mutation causes an increase in the reuptake of serotonin, which means there are lower levels of serotonin in the synaptic gap
• How might the COMT gene cause OCD?

  • regulates dopamine production
  • people with OCD are more likely to have a particular mutation of this gene
  • this causes lower activity of the COMT gene and higher levels of dopamine