Biological explanations of OCD

• There are two biological explanations for OCD: genetic explanation and neural explanation, which includes brain abnormality and neurotransmitters.
• The genetic explanation suggests that a gene can be inherited from parents that predisposes the individual to develop OCD.
• Twin studies have been conducted to investigate the heritability of OCD, comparing the concordance rates of OCD in MZ twins compared to DZ twins.
• MZ twins share 100% of their genes and are more likely to have the same disorder as DZ twins share 50% of their genes.
• Biological explanations of obsessive compulsive disorder (OCD) suggest that low serotonin is a causal factor.
• Comparison with other explanations is necessary.
• Credit other relevant material.
• Not all patients respond to drug treatment, which casts doubt on the validity of the explanation.
• Some studies of abnormal brain functioning, such as Aylward, have not been replicated.
• Many neural mechanisms have been identified but these are not always present in all cases.
• Neurochemical imbalances or structural abnormalities in the brain may be a symptom rather than the cause of the illness.
• Nestadt et al (2010) compared the concordance rates for OCD between MZ and DZ twins and found that MZ twins had a 68% concordance rate and DZ twins had a 31% concordance rate.
• The gene that regulates dopamine is known as the COPD gene.
• The biological explanation of OCD is criticised for emphasising free will.
• The worry circuit for OCD involves the OFC, thalamus and caudate nucleus.
• The genetic and neural explanations of OCD are described and evaluated.
• Cromer reported that ¾ of OCD patients had experienced a traumatic life event.
• The SERT gene variation leads to higher levels of serotonin.
• One study that supports the involvement of the worry circuit in OCD was by Raxena and Sauch.
• The biological explanation of OCD is criticised for being reductionist.
• The biological explanation of OCD has useful application to CBT.
• The concordance rates for OCD are higher in MZ twins than DZ.
• Two specific genes have been associated with OCD: variations in the COMT and SERT genes.
• The COMT gene is associated with the production of an enzyme, which regulates the neurotransmitter dopamine.
• One variation of the COMT gene results in higher levels of the neurotransmitter dopamine.
• Kumar and Rai (2020) found that this variation of the COMT gene is more common in patients with OCD, in comparison to people without OCD.
• Dopamine is thought to play a role in the drive to engage in compulsive behaviours.
• The SERT gene, also known as the 5-HTT gene, affects the transport of serotonin.
• When a pleasurable experience occurs, dopamine elevation in the brain creates the sensation of pleasure.
• Different combinations of genes may also account for different types of OCD.
• The neural explanation implicates the activity of neurotransmitters including dopamine and serotonin.
• OCD is thought to be a continuation of the dopamine reward sensation, where the completed compulsion lessens the anxiety and provides relief from the obsessive thoughts.
• Dopamine is usually an excitatory neurotransmitter and abnormally high levels of dopamine have been suggested to cause OCD.
• Over time, the anxiety associated with obsessive thinking is stopped only by the pleasure of completing the compulsion.
• Dopamine is a neurotransmitter linked with memory, learning, concentration, motor control and experiencing motivation and rewards.
• The neural explanation of OCD focuses on brain differences that could cause OCD, considering both brain chemistry (i.e. neurotransmitters) and brain structures.
• The genetic explanation for obsessive-compulsive disorder (OCD) suggests that OCD is an inherited condition, with vulnerability/predisposition passed on across generations.
• A number of candidate genes have been implicated as a possible cause for OCD, with Taylor (2013) identifying up to 230, suggesting OCD is polygenic.
• There is aetiological heterogeneity in OCD, meaning different combinations of genes may cause the disorder in different people.
• One variation of the SERT gene causes an increase in transporter proteins at a neuron’s membrane, decreasing the levels of serotonin in the synapse.