Biological approach to explain and treat OCD

• What are the assumptions of the biological approach to explaining OCD?

  -Suggests that OCD is inherited and that individuals receive specific genes from their parents which influence the onset of OCD

  -Suggests that abnormal levels of neurotransmitters and certain regions of the brain are implicated in OCD
• Define polygenic

  Several genes involved
• Describe the genetic explanation

  OCD can be inherited. OCD sufferers are more likely to have a family member with OCD and therefore candidate genes are involved in the vulnerability to OCD. The genes involved are dopamine and serotonin as they have a role in regulating mood
• Describe the COMT gene

  Responsible for an enzyme called COMT which regulates levels of the neurotransmitter, dopamine

  The abnormal low activity variant of this gene produces an insufficient amount of COMT, causing an inability to regulate dopamine levels

  Results in the production of abnormally high dopamine levels, which is linked to symptoms of OCD such as obsessions and compulsions
• Describe the SERT gene

  Responsible for influencing transportation of the neurotransmitter serotonin. A mutation of the SERT gene affects the transportation of serotonin between neurons by creating abnormally low levels of the neurotransmitter

  Low levels of serotonin has been linked to OCD symptoms such as obsessions and anxiety
• Describe the neural explanation

  Neurochemistry refers to processes involved in sending messages through the nervous system:

  • OCD can be caused by abnormally high levels of the neurotransmitter, dopamine
  • It is an excitatory neurotransmitter so high levels influences concentration and creates an inability to stop focusing on obsessive thoughts and repetitive behaviour
  • OCD can also be caused by abnormally low levels of the neurotransmitter, serotonin
  • It is an inhibitory neurotransmitter so low levels of it mean that repetitive behaviours/thoughts are not being switched off as normal
• Describe how abnormal brain circuits cause OCD

  -The OFC responds to sensory information from the environment and turns it into thoughts and action

  -Hyperactivity in the OFC is thought to lead to exaggerated worry responses so a signal is sent to the thalamus to prepare for threat

  -The caudate nucleus (in the basal ganglia) which controls routine behaviours and habits would normally suppress the threat if it was minor. In OCD sufferers, it sends out a signal of threat when there is none because it is damaged

  -The threat signal is sent back to the OFC to create a worry circuit loop
• What does OFC stand for?

  Orbitofrontal cortex
• What are the key assumptions of the biological approach to treating OCD?

  The suggestion that OCD is caused by low levels of the neurotransmitter serotonin means that it can be treated by prescribing drugs, such as antidepressants, which will improve mood and reduce anxiety
• Describe a tricyclic

  Oldest form of anti depressant

  Increases levels of serotonin and noradrenaline
• Describe a SSRI

  Selective serotonin re-uptake inhibitor

  Increases serotonin
• Explain how an anti depressant works

  -Electrical impulses trigger the release of neurotransmitters from the pre-synaptic neuron

  -When neurotransmitters cross the synapse they bind to receptor sites on the post-synaptic neuron

  -The neurotransmitters are then reabsorbed by the pre-synaptic neuron in a process called re-uptake, where they are broken down and reused

  -Tricyclics and SSRI's bind to receptor sites on the post-synaptic neuron, preventing re-uptake of serotonin

  -This increases the activity of serotonin neurotransmitters

  -This reduces OCD symptoms of obsessions
• Describe how antianxiety drugs are used in the treatment of OCD

  -Benzodiazepines such as Xanax enhance the action of the neurotransmitter, GABA

  -This has a naturally calming influence because it slows down neuronal activity as it is an inhibitory neurotransmitter

  -BZ's increase the efficiency of GABA - making it do its 'calming' job better by reacting with GABA sites

  -This means that activity in the central nervous system is slowed down

  This reduces OCD symptoms of compulsion