5.6 The Biological Approach to explaining OCD

5.6 The Biological Approach to explaining OCD

1. Genetic Explanations

   • Aubrey Lewis (1936)
     • 37% had parents with OCD
     • 21% had siblings with OCD
     • Suggests that OCD runs in families although what is passed down could be more commonly known as genetic vulnerability.
   • Candidate Genes
     • Genes which have been implicated in the development of OCD.
       • E.G The SERT gene which is involved with regulating serotonin
       • E.G The COMT gene, regulating the function of dopamine.
   • OCD is polygenic
     • Caused by the development of as many as 230 genes
   • Different types of OCD
     • One group of genes may cause OCD in one person but a different group may cause the disorder in another person.
   • Evaluation
     • Strengths
       • Research support.
         • Nestadt et al (2010) reviewed twin studies. Found that 68% of identical twins shared OCD but only 31% of non identical.
         • Marini and Stebnicki (2012) Family studies. Found that when one family member is diagnosed with OCD, the rest are 4 times as likely to be diagnosed.
     • Weaknesses
       • Environmental Factors
         • Individuals may gain vulnerability to OCD through an environmental stressor.
           • Cromer (2007) found that over half of the OCD patients in the sample developed OCD after a traumatic event in the past.
       • Too many genes involved to pinpoint specific ones.

2. Neural Explanations

   • Abnormal levels of certain neurotransmitters
     • If a person has low levels of serotonin then normal transmission of mood-relevant information does not take place and a person may experience low moods.
   • Certain brain circuits may be faulty
     • Basal Ganglia
       • Hypersensitivity of basal ganglia results in a rise of repetitive motor behaviours.
     • Orbitofrontal Cortex and Thalamus
       • Involved with decision making. An overactive thalamus would result in increased motivation to clean or check for safety. An overactive OFC means increased anxiety.
   • Evaluation
     • Strengths
       • Antidepressants which work purely on serotonin help in reducing OCD symptoms suggesting serotonin is involved in the process of OCD.
       • Brains of OCD patients are structured differently which can be seen in brain scans.
     • Weaknesses
       • Cant distinguish whether low dopamine is a factor in OCD or just an effect of OCD.