Biological explanations for depression

• Outline the neural explanation for OCD - worry circuit

  One neural explanation for OCD suggests there is a fault in the worry circuit of the brain i.e. a loop Involving three brain regions: the orbitofrontal cortex (OFC),

  the caudate nucleus and the thalamus.

  People with OCD are proposed to have a damaged caudate nucleus whereby it fails to suppress worry signals being sent from the orbitofrontal cortex (OFC) to the thalamus. This results in the thalamus becoming hyperactive, turning the worries into obsessions.
• Outline the neural explanation for OCD - abnormalities

  Other neural explanations suggest that OCD is caused by abnormalities in the levels of neurotransmitters in the brain. For example, serotonin helps to regulate mood, so people with OCD are proposed to have low levels of serotonin which leads to their obsessive thinking and anxiety. Meanwhile, dopamine is linked to reward-seeking behaviour so people with OCD are proposed to have high levels of dopamine which leads to their compulsions (as they provide a sense of reward by reducing anxiety).
• Outline the genetic explanation for OCV - SERT gene

  People with OCD may have inherited an overactive SERT gene which Is responsible for the re-uptake serotonin out of the synapse. An overactlve SERT gene results in too much serotonin being re-uptaken and thus too little serotonin left in the synapse. As serotonin helps to regulate mood, low levels of this neurotransmitter explain the obsessive thoughts and anxiety seen in people with OCD.
• Outline the genetic explanation for OCD - COMT gene

  People with OCD may have also inherited an underactive COMT gene which is responsible for producing enzymes that break down dopamine.

  An underactive COMT gene results in too little enzymes and, in turn, less dopamine being broken down.

  As dopamine plays a role in reward-seeking behaviour, high levels of dopamine have been linked to the compulsive behaviours seen in OCD (as they provide a

  sense of reward by reducing anxiety).
• Strength of neural expl. is - support evidence

  brain scanning studies comparing people with OCD to controls found that people with OCD had higher brain activity in their OFC and reduced brain tissue in their caudate nucleus. This is a strength as it supports the

  proposal that people with OCD have abnormalities in the worry circuit of their brain. Therefore adds credibility. 
• Strength of genetic expl. has supporting evidence

  strength of the genetic explanation for OCD is that it has received supporting evidence. E.g. twin studies have found higher concordance rates for OCD in MZ twins (who share 100% of their genes) than in DZ twins (who share 50% of their genes). This is a strength because the higher concordance rates in MZ twins can be explained by the fact that they share more similar genetics and so supports the proposal that genetics play a role in OCD. Therefore adds credibility.
• neural/genetic - practical application

  neural/genetic explanations is that they have resulted in practical applications when it comes to treating OCD. E.g. based on the proposal that low serotonin levels/an overactive SERT gene can lead to obsessions, drugs such as SSRls have been developed. These drugs block the re-uptake of serotonin,increasing its levels in the synapse. strength because these drugs are found to be effective at reducing symptoms of OCD and, if the treatment developed out of the explanation is effective, the explanation Itself must have merit. adds credibility.
• Neural/genetic expl. - overly focsued on nature

  For example, drug therapy is only effective in approximately 50% of people with OCD. This is a limitation because these individual differences suggest there may be other causes of OCD in some people. Indeed, the nurture perspective would argue that there may be environmental causes for OCD given that over half of people with OCD are found to have experienced a traumatic event in their past. Therefore questions credibility.
• Neural/genetic expl. - too bio deterministic

  This is because they attempt to explain the complex disorder of OCD by reducing it down into basic biological components i.e. either neural or genetic factors. This is a limitation because research has found that drug therapies for OCD are only effective in approximately 50% of people, suggesting there may be other contributing factors.
• Neural/genetic expl. too bio deterministic - diathesis—model

  researchers are now more likely to explain OCD through a diathesis-stress model. This proposes that OCD will only develop in individuals who have a

  vulnerability to developing the disorder (e.g. a genetic/neural vulnerability) as well as a stressor (e.g. experienced a traumatic event). This means that genetic or neural factors alone are not considered enough for OCD to develop. Therefore questions credibility.