The Biological Approach to Explaining OCD

• The Biological Approach to Explaining Obsessive Compulsive Disorder

  Genetic Explanations for OCD

  Neural Explanations for OCD
• Genetic Explanations for OCD (The genetic explanation)

  •OCD is inherited through genetic transmission.

  •Family studies have shown relatives of OCD sufferers have a greater tendency to suffer from OCD and anxiety related problems themselves.

  •Pauls et al (2005) found 10% of people with a first degree relative with OCD also suffered from the disorder compared to 2% of people in the general population.
• EVALUATION OF THE GENETIC EXPLANATION FOR OCD

  Research Support

  Environmental Influences

  OCD is Polygenic

  Further Research Needed
• Research Support

  • Twin studies show that 68% of identical twins (MZ) share OCD compared to 31% of non-identical twins (DZ). (Nestadt et al., 2010)
  • Family studies indicate that a person with a family member diagnosed with OCD is around four times as likely to develop it as someone without (Marini and Stebnicki, 2012).
• Environmental Influences

  • Parental Influence: Children have an 11% chance of developing OCD if a parent has the condition, indicating environmental factors' significance.
  • Traumatic Experiences: Cromer et al (2007) found that over half of OCD patients had traumatic experiences, suggesting environmental stressors impact OCD severity.
• OCD is Polygenic

  • Multiple Genes: OCD is likely influenced by a combination of genes like COMT and SERT, rather than a single gene.
  • Genetic Vulnerability: Each genetic variation only slightly increases the risk of OCD, indicating a complex genetic interplay.
  • Lack of Consistency: Psychologists struggle to identify all genes involved in OCD, leading to inconsistent research findings.
• Further Research Needed

  • Heritability of OCD: Pato (2001) suggests the need for more research on the heritability of OCD due to limited understanding of genetic mechanisms.
  • Subtypes and Genetic Factors: Different genetic factors may contribute to various OCD subtypes like hoarding or tic-related, indicating a complex genetic landscape.
  • For example, Hemmings et. al. found that a defect in a gene for dopamine was much less common in people with early onset than late onset OCD.
• Candidate genes

  •Candidate genes (specific genes that create a vulnerability) have been identified for OCD…

  •A faulty SERT (SERotonin Transporter) gene (5-HTTLPR variant) decreases levels of serotonin.

  •Low levels of serotonin has been linked to an inability to supress repetitive thoughts that characterise OCD.
• Abnormal Levels of Neurotransmitters

  •It is thought that lower levels of serotonin are associated with OCD as it has a role in preventing the repetition of tasks.

  •A lack of serotonin therefore results in the loss of a mechanism that inhibits task repetition.

  •Pigott et al. (1990) Found anti-depressant drugs that increase serotonin activity have been shown to reduce OCD symptoms.
• Abnormal Brain Circuits

  •Several areas in the frontal lobes of the brain are thought to be abnormal in people with OCD.

  •The orbitofrontal cortex (OFC) sends ‘worry’ signals, such as a potential germ hazard.

  •When the caudate nucleus (in the basal ganglia) is damaged it fails to suppress minor ’worry’ signals from the OFC.

  •The thalamus is alerted and confirms the ‘worry’ to the OFC creating a worry circuit.
• Research Support for the Neural Explanation of OCD

  • PET scans during active symptoms reveal heightened activity in the orbitofrontal cortex (OFC), while neuroimaging consistently shows excessive activity in the caudate nucleus among OCD patients.
  • Hu (2006) found lower serotonin levels in OCD patients compared to non-sufferers, supporting the association between low serotonin levels and OCD.
  • Combined, this evidence strongly supports the neural explanation for OCD, suggesting that certain brain circuits and neurotransmitter levels play significant roles in the disorder.
• Mixed support for the role of serotonin in OCD

  • SSRIs and Treatment: While SSRIs, which increase serotonin levels, can effectively treat OCD symptoms, the exact role of serotonin in OCD is unclear.
  • Mixed Findings: Bastani et al. (1990) found that increasing serotonin levels can worsen OCD symptoms, suggesting a complex relationship between serotonin and OCD.
  • Other Neurotransmitters: Dopamine and glutamate have also been implicated in OCD, raising questions about the sole role of serotonin in the disorder.
• Cause and Effect

  • Brain Activity Association: Brain scan studies associate increased activity in certain brain areas (e.g., OFC, caudate nucleus, serotonin) with OCD, but this does not establish causation.
  • Consequence vs. Cause: Biological abnormalities observed in scans may be consequences of OCD rather than its cause.
• Alternative Explanations

  • SSRIs and Limitations: While SSRIs provide relief for some OCD sufferers, not all cases respond to these medications, indicating that abnormal serotonin levels may not fully explain OCD.
  • Psychological Explanations: Conditioning and cognitive factors, such as those addressed in cognitive-behavioral therapy (CBT), offer strong competition to the biological model in explaining OCD.
  • Therefore, a more holistic approach that considers biology, conditioning and cognitions may provide a better explanation for OCD than biology alone.