biological approach to explaining OCD

• two biological expanations

  1. genetics
  2. neural factors
• genetic explanation

  • (partially) phenotype of OCD will be the result of one's genotype
  • expect it is hereditary = runs in family
  • genetic explanation often studied using twin, adoption or family studies
  • concordance rates identify % of twin pairs or other relatives who have OCD
  • concordance rates likely higher when genetically similar
  • OCD is polygenic = not caused by a single gene but many
• two candidate genes

  • SERT gene
  • regulates serotonin levels, creating lower levels of neurotransmitter
  • important as low serotonin levels have been implicated in OCD
  • this link may be associated with obessessions in particular
  • COMT gene
  • regulates to production of dopamine
• ao3 on genetic explanation

  could be a learnt charactersitic through OCD
• concordance

  % agreement rate between twins sharing a disorder
• research on genetics

  bellodie et al (2001)

  • genetics/OCD play a role in disorder
  • evidence from twins + fam structure = showed close relatives more likely to have disorder than a more distant relative
• neural explanation

  • suggest that abnormal neurotransmitter levels and brain circuits are responsible for OCD symptoms
  • eg. lower serotinin levels
  • may lead to functional differences in the brains of people with OCD, where parts of the brain are more/less active than people without the condition
• neuroimaging techniques (brain scan) enable to study brain in detail + identify brain patterns - allows for comparisons with abnormal brain patterns
• brain dysfunction in OCD

  basil ganglia:

  hypersensitive in the brain = affects the psychomotor actions = repetitive actions in OCD

  eg, washing/checking/cleaning (compulsions)
• brain dysfunction in OCD

  orbital frontal cortex (OFC):

  part of thalamus (is overactive) = cleaning, checking behaviour (obsessions) = anxiety
• cycle

  • germs = OFC send signal to thalamus
  • supresses thoughts (normal) = caudate nucleus is normal
  • if caudate nucleus is damaged = thalamus is alerted = checking/cleaning (compulsion) and confirms worry to OFC
• strengths

  supporting research from twin + family studies for the role of genetics on OCD

  • billet et al (1998) = meta-analysis of 14 twin studies of OCD. found MZ twins twice likely to suffer from OCD (68%) than DZ twins (31%)
  • however, as concordance rates are not 100%, other factors must contribute to OCD
• strengths

  • evidence suggests there is a genetic component to the disorder. one of the best sources of evidence for importance of genes is twin studies (Nestadt, 2010)
  • family studies would also be used to explain environmental influences (can be a limitation)
• weakness of genetic explanation

  • close relatives of OCD sufferers may have observed and imitated behaviour (SLT)
  • it is difficult to untangle the effects of environment and genetic factors
• strength

  supporting research for neural explanations:

  • evans et al (2004) found patients with OCD exhibited 'functional hyperactivity' in orbitofrontal cortex, compared to controls
  • the degree of hyperactivity also correlated to symptom severity
• strength

  role of neurotransmitters:

  • allows medication to be developed which helps sufferers
• weaknesses

  • drugs not completely effective
  • just because administering SSRIs decrease OCD symptoms does not mean that this was the cause in the first place
  • there is time delay between taking drugs to target the conditions and any improvements being made and yet the chemical imbalance is addressed in hours
• SSRIs = serotonin selective reuptake indicators

  (anti depressants)
• strength

  biological explanation supported by the success of biological treatments

  • zohar et al. (1996) found SSRIs reduced symptoms in 60% of OCD patients
  • this supports the neural explanation of OCD + suggests neurotransmitters may be part of cause of condition
  • however, link betw. serotonin + OCD is correlational, meaning decreased serotonin levels may be an OCD symptom, rather than a cause
  • in addition, the treatment aetiology fallacy suggests that a successful treatment may not actually tell us anything about the cause of a condition
• limitations

  ignores other factors and is reductionist

  • does not take into account cognitions (thinking) and learning. some behaviourists suggested OCD may be learnt and maintains through a 'two process theory'
  • an explanation that ignores these other factors may be oversimplistic, and fail to give a full explanation of the condition
  • a diathesis-stress explanation may be more appropriate