Biological explanations for OCD

• The biological approach argues that OCD, an anxiety disorder characterised by obsessive thinking and repetitive behaviours, is caused by abnormal functioning of neural mechanisms, neurotransmitter and hereditary influences (genetic inheritance and transmission). There are two main biological explanations for OCD: Genetic explanations - which suggest that faulty genes responsible for mental disorders are under hereditary influences through genetic transmission from parent to offspring.
• The COMT gene may contribute to OCD. This gene regulates the levels of dopamine. One allele of the gene leads to lower activity of the gene. This leads to higher levels of dopamine. This is associated with OCD (compulsive behaviours- overactivity in basal ganglia impacts the caudate nucleus).
• The SERT gene is responsible for regulating transportation of serotonin. One allele of the SERT gene affects the transportation of serotonin. This leads to lower levels of serotonin. This is associated with OCD (obsessive thoughts-higher levels of activity in OFC).
• There are also neural explanations for OCD, the occurrence of OCD through abnormal functioning of neural mechanisms and neurotransmitters. OCD is also associated with higher levels in the OFC. The OFC sends minor worry signals.
• The caudate nucleus is thought to normally suppress signals from the OFC, but when it is damaged the minor worry signals are not suppressed. Thus activity levels in the OFC increase and consequently the thalamus has more impulses to act on/create than normal, these impulses turn into obsessions (as the thalamus sends a signal back to the OFC which creates the worry circuit) and worries become obsessions and impulses to act become compulsions.
• Serotonin and dopamine play roles in this system as they are linked to these regions of the frontal lobes. Serotonin plays an important role in the operation of OFC and caudate nuclei and dopamine is the main neurotransmitter of the basal ganglia, so abnormal levels of each may cause malfunctioning.
• There is evidence to support the OCD has a genetic basis, therefore biological. Using a meta-analysis of 14 twin studies Billet et al (1998) found that, on average, monozygotic (MZ) twins were more than twice as likely to develop OCD if their co-twin had the disorder, the chances of developing OCD was lower for the co-twin of a dizygotic (DZ) pair. This is a strength because the research suggests that genetics does paly a part in the development of OCD. If there was no genetic aspect, then there would be no difference in the chance of developing OCD,like a co-twin, between MZ and DZ twins.
• However, a weakness of using Twin studies to support the genetic explanation of OCD is that the concordance rate is not equivalent to the percentage of genes shared by MZ twins. For example, the concordance rate for MZ twins is not 100% when they share 100% of their genes. This clearly is a weakness of the genetic explanation for OCD as it suggests that the environment must play some role in the development of the anxiety disorder, such as stress levels. This implies that the genetic explanation is not a completely valid explanation of OCD.
• There is lots of undermining evidence for both biological explanations of OCD as by solely honing in on the biological causes of OCD it undermines the effects of the environment. Environmental factors can also trigger or increase the risk of developing OCD. For example it has been found that over half of OCD patients in one study had a traumatic experience In their past and that OCD was more severe in participants with more than one trauma.
• Continuing weakness;

  This clearly is a weakness of using the biological approach solely to explain OCD as this suggests that OCD cannot be entirely biological in origin (in some cases). Thus It may be more productive to focus on the environmental causes of OCD.
• On the contrary there is some evidence to support the neural explanation of OCD and the role of neural mechanisms in OCD. For example, antidepressants that only alter levels of serotonin have been effective in reducing OCD symptoms. This clearly supports the neural explanations of OCD as it suggests that the serotonin system must be involved in OCD for this antidepressant to be effective. Since it was we can suggest that the theory has some validity and so should be used to explain OCD.