Biological Explanation of OCD

Question 1

What are the two biological explanations of OCD?

Answer 1

Genetic, and neural explanations.

Question 2

Genetic Explanation

Answer 2

Suggests that OCD is down to genes that can be passed down through families. Meaning, we may be genetically pre-disposed to OCD.

Question 3

COMT Gene

Answer 3

Regulates production of dopamine. This gene is mutated in OCD patients, affecting levels of dopamine.

Question 4

Tukel et al. (2013) - Summary

Answer 4

Compared 101 OCD patients to 100 healthy controls. Found that the OCD patients had lower activity in the COMT Gene, meaning for higher levels of dopamine.

Question 5

SERT Gene

Answer 5

Regulates production of serotonin. This gene is mutated in OCD patients, leading to reduced levels of serotonin.

Question 6

Ozaki et al. (2003) - Summary

Answer 6

Found the mutated SERT Gene in two different families. Six out of the seven families members had OCD.

Question 7

Monozygotic Twins

Answer 7

Twins who came from one egg, sharing 100% of DNA.

Question 8

Dizygotic Twins

Answer 8

Twins who came from two separate eggs, sharing 50% of DNA.

Question 9

Concordance Rates

Answer 9

The degree of genetic similarity for a particular trait.

Question 10

Nestadt et al. (2010) - Summary

Answer 10

Reviewed all genetics and OCD research with twin studies to date. Found that the concordance rates in monozygotic twins were higher than dizygotic twins. Monozygotic was 68%, dizygotic was 31%.

Question 11

How do we know that genetics are not the only factor is the development of OCD?

Answer 11

If genetics was the only factor, concordance rates between monozygotic twins would be 100%, as they share 100% of DNA. Therefore, other factors must be involved, such as the environment.

Question 12

Neural Explanation

Answer 12

Suggests that OCD is down to different levels of neurotransmitters, and abnormal brain structures.

Question 13

How do dopamine levels link to OCD?

Answer 13

It has been found that higher levels of dopamine link to OCD, specifically symptoms such as compulsive behaviours.

Question 14

Kim et al. (2007) - Summary

Answer 14

Gave OCD patients drugs that affected their dopamine levels. They found that lowered levels of dopamine was correlated with less compulsive behaviours.

Question 15

How do serotonin levels link to OCD?

Answer 15

It has been found that lower levels of serotonin link to anxiety and OCD. This may be because in those with OCD, serotonin is removed too quickly from the synapse, before it has been transmitted.

Question 16

Soomro et al. (2009) - Summary

Answer 16

Reviewed 17 studies for drug treatment of OCD, studying over 3000 participants. Compared drugs that increase serotonin levels with placebos. They found that the drugs altering serotonin levels were more effective in reducing OCD symptoms.

Question 17

Orbito-Frontal Cortex

Answer 17

Located in the pre-frontal cortex, above the eye sockets, sometimes called the ‘worry circuit’. The worry circuit includes the orbito-frontal cortex, the basal ganglia, and thalamus.

Question 18

How does the ‘worry circuit’ work?

Answer 18

The orbito-frontal cortex is involved in our perception of the world. When we are worried, it will signal to the thalamus. The worry signal is normally suppressed by the basal ganglia.

Question 19

What happens to the ‘worry circuit’ in those with OCD?

Answer 19

The basal ganglia may be abnormal in those with OCD, causing the thalamus to be strongly alerted, confirming the worry to the orbito-frontal cortex. This is associated with decision-making and logical thinking, causing the person to start worrying and obsessing over this. The worry circuit is over-active, which may lead to compulsive behaviours to deal with the worries.

Question 20

Buecke et al. (2013) - Summary

Answer 20

Investigated OCD patients who were either on medication or not. Those not on medication had more activity in their orbito-frontal cortex, and the higher the activity, the more severe their OCD symptoms were.

Question 21

Biological Explanation - Strengths

Answer 21

• Practical application with treatments. With biological factors being involved such as serotonin, it is easier to treat OCD by simply using drugs to increase levels of serotonin - SSRIs.

Question 22

Biological Explanation - Limitations

Answer 22

• Limited usefulness as it tends to explain the symptoms of OCD, rather than the cause.
• Alternative explanation from the Diathesis-Stress Model, combining biological and environmental factors.
• Contradictory evidence from Cromer et al. (2007) - studied a sample of OCD patients, and found that over 50% of them had experienced a traumatic event in their past.
• This explanation is very deterministic, suggests that OCD patients do not have any free will over their likelihood of developing the disorder.