OCD - Biological Flashcards
The biological approach to explaining OCD
Genetic Explanations such as the COMT gene, the SERT gene and Diathesis-stress.
Or
Neural Explanations such as Abnormal levels of neurotransmitters and Abnormal brain circuits.
Genetic Explanations:
The COMT gene
The COMT gene is associated with the production of , which regulates the neurotransmitter dopamine.
One variation of the COMT gene results in higher levels of dopamine and this variation is more common in patients with OCD, in comparison to people without OCD.
Genetic Explanations:
The SERT gene
The SERT gene is linked to the neurotransmitter serotonin and affects the transport of the serotonin , causing lower levels of serotonin which is also associated with OCD (and depression)
Genetic Explanations:
Diathesis-stress
Individual Genes may create a vulnerability for OCD, which is only expressed if particular stressors are present. Some people could posses gene variations but suffer no stressors and, therefore no ill effects
Neural Explanations:
Abnormal levels of neurotransmitters
Dopamine levels may be abnormally high in people with OCD since dopamine-enhancing drugs induce stereotyped movements resembling compulsive behaviour of OCD in animals. Lower serotonin levels are associated with OCD; Antidepressent drugs that increase serotonin can reduce OCD symptoms
Neural Explanations:
Abnomrla brain circuits
Several areas in the frontal loves of the brain are thought to be abnormal in people with OCD. The orbitofrontal cortex sends ‘worry’ signals to the thalamus.
These are normally suppressed by the caudate nucleus but if this is damaged, the thalamus is alrted and confirms the ‘worry’ to the OFC creating a worry circuit
Evaluation of the Biological approach to explaining OCD:
Family and Twin Studies
Compared to the general population, people with a first degree relative with OCD have a five times greater risk of having the illness at some time.
Compared to non-identical twins, identical twins are more than twice as likely to develop OCD if their co-twin has it.
Concordance rates are never 100% however, so environmental factors must contribute.
Evaluation of the Biological approach to explaining OCD:
Tourette’s syndrome and other disorders
Genes may merely predispose individuals towards obsessive type behaviour.
Psychologists argue that OCD is one expression of the same gene that determines touretts syndrome.
OCD symptoms are also present in autism and anorexia and two out of every three OCD patients also experience at least one episode of depression.
There is, therefore no one gene directly and exclusively responsible for OCD
Evaluation of the Biological approach to explaining OCD:
Research support for genes and OFC
Many studies demonstrate the genetic link to abnormal levels of neurotransmitters.
Compared to unrelated health people.
OCD patients and their close relatives had reduced grey matter in Key regions of the brain including the OFC.
Anatomical differences are inherited and these may lead to OCD in certain individuals
Evaluation of the Biological approach to explaining OCD:
Alternative explanations
The Two-process model is a credible, alternative, behaviourists explanations for OCD.
A link between dirt and anxiety persists because compulsions such as hand washing reduce the anxiety.
This explanation is supported by an improvement rate in up to 90% of cases following treatment for OCD called exposure and response prevention.
The Biological approach to treating OCD:
Drug Therapy:
Antidepressants such as SSRIs and Tricyclics. Anti-Anxiety Drugs or Other Drugs
The Biological approach to treating OCD:
Antidepressants of SSRIs
Low levels of the neurotransmitter serotonin are associated with depression. as well as OCD. So antidepressants are used to increase levels of serotonin in both disorders. They may normalise the ‘worry circuit’.
Antidepressants also reduce anxiety associated with OCD. Selective serotonin re-uptake inhibitors are currently the preferred drug for treating anxiety disorders.
They increase levels of the serotonin thus regulating mood and anxiety
The Biological approach to treating OCD:
Tricyclics
The antidepressant tricyclic clomiphramine is today primarily used in the treatment of OCD rather than depression.
Tricyclics block the mechanism that re-absorbs both serotonin and noradrenaline prolonging their activity. Tricyclics have the advantage of targeting more than one neurotransmitter, however they have greater side effects so are used as a second-line treatment for patients where SSRi were not effective.
The Biological approach to treating OCD:
Anti-anxiety Drugs
BZ’s are commonly used to reduce anxiety. Bz’s slow down the activity of the central nervous system by enhancing the activity of the neurotransmitter GABA.
This is the neurotransmitter that has a general quietening effect on many of the neurons in the brain by reacting with special sites on the outside of neurons.
Evaluation of the Biological approach to treating OCD:
Effectiveness
Soomro reviewed 17 studies of the use of SSRis with OCD patients and found them to be more effective than placebos in reducing the symptoms of OCD up to three months after treatment.
However most studies are only of three to 4 months duration and therefore little long-term data exists.
