Biological approach to OCD

• Genetic explaination-

  • Lewis (1936) – OCD patients 37% had parents with OCD, 21% had siblings with OCD, suggesting that OCD runs in families.
  • Diathesis-stress model states that there’s a certain gene that makes people more likely to develop a mental disorder, environmental stress triggers it.
  • Candidate genes are vulnerable for OCD (the genes that regulate serotonin like 5HT1-D beta is implicated in the transport of serotonin across synapses.
• Genetic explaination-

  • OCD is polygenic so it’s a combination of genetic variations that increase the vulnerability (Taylor 2013 analysed findings from a previous study and found 230 different genes involved in OCD.
  • OCD genes are associated with dopamine, serotonin which both regulate mood.
  • Aetiologyically heterogeneous - the genes are different in everyone that create OCD. (origins (A) vary in everyone (H)).
• Genetic explanation-

  • S- Nestadt et al 2010 reviewed twin studies- 68% of identical twins share OCD, 31% of twins share OCD.
  • CPS- Animal studies show that particular genes are associated with repeated behaviours in other species like mice (Aymara 2016).
  • CPW- Human mind is different from animals as its more complex, so animal studies cat be generalised.
  • W- Environmental factors have a larger impact - Cromer et al 2007 found over ½ of OCD patients in the sample had gone through a traumatic event, which made the OCD more severe.
• Neural explanation-

  • Neurotransmitter of serotonin helps regulate moods, if there’s a low level of serotonin the neurotransmitter can’t relay its mood-relevant information onto other neurones, making people experience low moods.
  • The frontal lobe is associated with decision making and abnormal functions, as well as logical thinking.
  • Parahippocampal gyrus is associated with processing unpleasant emotions which functions abnormally with OCD.
• Neural explanation-

  • S- Serotonin antidepressants reduce the symptoms of OCD by increasing levels at the neurones.
  • S- Brain dysfunction causes OCD through the serotonin neurone not working properly.
  • W- The link between OCD and serotonin isn’t unique, comorbidity between OCD and clinical depression is common, both having disruption due to serotonin, so its not unique.
  • W- Correlation between neural abnormality and OCD doesn’t mean they’re linked, since there could be. 3rd factor or comorbidity.