Biological approach to explaining OCD

Question 1

What are obsessive thoughts and compulsive behaviours

Answer 1

-Obsessive thoughts are repetitive mental images or concerns that provoke anxiety
-Compulsions are actions that the sufferers of OCD feel they need to take in order to reduce the anxiety cause by the obsessive thoughts
-Unfortunately the relief is only temporary as the obsessive thoughts soon return

Question 2

Genetic explanation of OCD intro

Answer 2

-The genetic explanation of OCD suggests that a genetic vulnerability or predisposition to OCD is inherited from our parents

Question 3

Genetic analysis + candidate genes + polygenic

Answer 3

-Genetic analysis has identified a large number of candidate genes which are more frequent in people with OCD
-Some of these include : SERT gene (influences serotonin reuptake), Gene 9, COMT gene and 5HT1-D beta gene
-As many candidate genes have been identified, this suggests that OCD is polygenic (a trait or disorder influenced by multiple genes)

Question 4

Evidence for genetic aspect of OCD (family studies)
-positive evaluation for biological explanations of OCD + negative evaluation (not 100% concordance rate)

Answer 4

-Family studies provide evidence for the genetic aspect (heritability of OCD
The general prevalence rate of OCD is 2%, meaning that the concordance rate between a person with OCD and a random person is 2%
-However, with OCD, the more closely genetically related two people are, the higher the concordance rate of OCD
-For example first degreee relatives have a concordance rate of 10%, DZ twins have a concordance rate of 31% (50% shared genes) and MZ twins have a concordance rate of 68% (100% shared genes)
-This supports the theory that a genetic predisposition to OCD is inherited
-HOWEVER, if genetics was solely responsble for the development of OCD, then the concordance rate of MZ twins would be 100% since they share 100% of their genes. Since the concordance rate is only 68%, this suggests that the genetic explanation of OCD is incomplete and that other factors (e.g environmental) influence the development of OCD

Question 5

Diathesis stress model (working on the family studies negative evaluation) as an explanation for OCD + research evidence (Cromer)

Answer 5

-Therefore a diathesis-stress model would be a more holistic explanation of OCD.
-Individuals inherit a genetic predisposition for OCD (diathesis), however the disorder only develops when there is an environmental trigger (stressor) e.g a traumatic life experience
-Cromer found that the majority of 256 participants with OCD had experienced at least one traumatic life event, and those who had experienced a traumatic life event tended to have more severe OCD symptoms; this provides evidence for the influence of environmental factors on the development of OCD

Question 6

Neural explanation for treating OCD intro

Answer 6

-Neural explanations include biochemical causes, imbalances of neurotransmitters, and large neural structures in the brain

Question 7

Influence of serotonin + SERT gene

Answer 7

-Low levels of serotonin are thought to cause obsessive thoughts
-This is likely cause by serotonin being removed from the synaptic cleft (reuptake) before it has a chance to influence the post synaptic cell/transmit its signal
-The SERT gene is responsible for the reuptake of serotonin into the pre synaptic neurone; it is suggested that individuals with OCD have a variation of this gene that causes the rapid reuptake of serotonin

Question 8

COMT gene (dopamine)

Answer 8

-The COMT gene is thought to balance dopamine levels; irregular dopamine levels are implicated with OCD, therefore COMT gene variations are thought to contribute to OCD as it cannot control irregular dopamine levels associated with compulsive thoughts

Question 9

Worry circuit

Answer 9

-The “worry circuit” is a set of brain structures that include the orbitofrontal cortex (OFC responsible for rational decision making), the basal ganglia and the thalamus
-Communication between these brain structures are thought to be overactive in people with OCD
-In normal functioning the basal ganglia filters out minor worries from the OFC, however if the basal ganglia is hyperactive, even small worrise get through to the thalamus
-The thalamus then passes it back to the OFC which forms a loop (source of the recurring obsessive thoughts)
-Compulsions (repetitive motor functions) are an attempt to break this loop

Question 10

Parahippocampal gyrus

Answer 10

-The parahippocampal gyrus is an area of the brain linked to OCD
-The parahippocampal gyrus is responsible for regulating and processing unpleasant emotions, and is thought to function abnormally in people with OCD

Question 11

Positive research evaluation + however (negative) -PET scans show, however evidence may be correlational