4.4.2 Biological Explanations of OCD

The biological approach is known as the medical model as it explains all behaviour through our biology. The biological approach sees OCD and other abnormalities in the same way it sees a physical illness, explaining it by abnormal biological processes.

Genetic explanations 

These are hereditary influences transmitted from parent to offspring by genetic transmission.

• Researchers have identified Candidate genes as genes that create vulnerability to OCD 
• OCD seems to be polygenic; this means OCD is not caused by one single gene but by a combination of genetic variations that together cause significantly increased vulnerability
• There are different types of genes that cause OCD and one gene variation or group of genes may cause it in one person, but another sufferer of OCD could have a different variation of genes
• Taylor (2013) found evidence from previous studies that there are up to 230 different genes which may be involved with OCD
• Genes studied in relation to OCD include those involved in the action of dopamine and serotonin and both neurotransmitters are believed to have a role in regulating mood
• Tukel et al. (2013) suggested a variation of the COMT gene may contribute to OCD as it is more common in patients who suffer from OCD than in those that do not. This variation produces higher levels of dopamine and lower activity of the COMT gene
• The 5-HTT gene has also been linked with OCD as it affects the levels of serotonin, making them less and these lower levels of the neurotransmitter are linked with OCD

Evaluation of genetic explanations

Strengths

Limitations

A strong evidence base of research, especially within twin studies. Nestadt et al. (2010) reviewed evidence that 68% of identical twins will both have OCD compared to 31% of non-identical twins. Marini et al (2012) found a person with a family member diagnosed with OCD is around 4 times as likely to develop it as someone without This is a significant link to show that genetics play an important role in the development of OCD and that nature (in the nature/nurture debate) is shown to play a large role here. Grootheest et al. (2005) found their genetic link was stronger in children that were sufferers of OCD.

Ignores environmental factors, although twin studies are used as there is a greater genetic link, these twins also share the same environment, which could trigger OCD. There is evidence to suggest that identical twins are treated 'more similar' in terms of their environment, (e.g. expectations, style of dress, extracurricular activities) than non-identical twins who are treated more as individuals.  Pato et al. (2001) noted that although there does seem to be a genetic link between OCD sufferers, there is not enough understanding about the actual genetic mechanisms causing OCD. Grootheest et al. (2005) found that the genetic link was stronger in children that were sufferers of OCD, than when the OCD originated in adulthood, showing the probability of different causes.

• OCD can also be explained through neural connections and the imbalance or damage these can have.
• The neural damage may have been caused by illnesses that affect the immune system, such as different bacterias, and the explanation links to the genetic difference that has been found in OCD sufferers, where the gene, influences the levels of key neurotransmitters and the structures in the brain.

Neural explanations

• Serotonin is known to play a role in regulating mood, if a person has low levels of serotonin, the person can have low moods and other mental processes are often affected
• The reduction of serotonin can explain some cases of OCD
• Dopamine levels are thought to be abnormally high in people who suffer from OCD 
• Abnormal brain circuits:
  • The orbital Frontal Cortex (OFC), sends signals to the thalamus about things that are worrying you, this area of the brain is overactive in people who suffer from OCD
  • The thalamus, which is the part of the brain that instructs the person to do a certain activity or behaviour, in OCD sufferers, this would be the ODC behaviour
  • The caudate nucleus is the part of the brain that in non-OCD suffers, surprises the messages from the OFC, and normalises the worry, however, in OCD suffers, this part of the brain is not completing this job and allows the OFC to make the sufferer worry. This could be due to damage or overstimulation
• Some forms of OCD have been linked with poor decision-making, which could be down to abnormal functioning in the lateral parts of the frontal lobes. (the parts of the brain responsible for logical thinking and making decisions)

Evaluation of neural connections 

Strengths	Limitations
Antidepressants such as SSRIs, which are used to control levels of serotonin, are seen to be effective in reducing OCD symptoms, which would support the idea of an imbalanced neural network.	There is evidence that environmental triggers can play a large role in triggering OCD, one study found over half the participants had suffered a traumatic event, and this led to their OCD. Not all OCD sufferers respond positively to antidepressants ( serotonin levelers), which would show it is not the neural network causing OCD in those patients.