AO1: Biological approach to explaining OCD

• Obsessions

  Internal components

  Cognitive aspect

  Intrusive thoughts
• Compulsions

  External component

  Behavioural aspect

  Repetitive acts to reduce anxiety
• Emotional aspect

  Anxiousness, guilt and disgust
• Cognitive aspect

  Obsessions, hypervigilance, catastrophizing
• Brain structure

  PET scans have revealed high activity in the orbital prefrontal cortex (OFC) when carrying out tasks that activate OCD symptoms.
• Brain structure: The worry circuit

  Caudate nucleus designed to supress minor worry signals from the OFC reaching the thalamus. However, the CN has low activity so is thought to be damaged in OCD patients. This means OFC signals cannot be supressed which causes the thalamus to overexcite. This therefore causes the person to worry 'too much'.
• Brain structure: The worry circuit

  The worry circuit is broken by compulsions.
• Serotonin

  Researchers know that OCD is triggered by communication problems between the brain's deeper structures and the front part of the brain. These parts communicate primarily by serotonin.
• Serotonin

  People with OCD are thought to have low serotonin. Serotonin is therefore unavailable to calm obsessions ad anxiety caused by it.
• Genetics: hSERT

  OCD may be associated with a rare combination of two mutations within the human serotonin transporter gene (hSERT). This causes the increased reuptake f serotonin in those neuronal synapses. hSERT works too fast, and may collect all the serotonin before the next cell has even heard the signal to absorb the transmitter.
• Genetics: hSERT

  hSERT mutations can therefore decrease the amount of serotonin available in the synapse for signalling. Leading to less serotonin available for neuronal communication so therefore inability to calm OCD.
• hSERT

  Involved in creating proteins which metabolise serotonin.
• Orbital Prefrontal Cortex

  Rationalises thinking
• Thalamus

  Processes information ('animal' brain)
• Caudate nucleus

  Supresses minor worry signals from the OFC
• Serotonin

  Regulates mood, calms you down and lowers anxiety