OCD (Biological)

  • Created by: bintahall
  • Created on: 09-05-19 11:46

Genetic Explanations for OCD

Genetic Explanations:

The COMT Gene: Regulates the production of dopamine. The gene comes in different forms - a certain form has found to be more common in OCD patients - produces lower activity of the COMT gene and higher levels of dopamine

The SERT Gene: Creates lower levels of serotonin. Higher levels of this gene is prominent in those with OCD

Diathesis-stress: Suggest that each gene only creates a vunerability for an individual developing OCD - a certain event may trigger the OCD

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Neural Explanations for OCD

Abnormal levels of neurotransmitters: Dopamine levels high in those with OCD - animal studies. Serotonin levels low in those with OCD - antidepressent drugs that increase serotonin activity shown to reduce OCD symtoms.

Abnormal brain circuits: Caudate neuclus normally supresses signals from the orbitofrontal cortex which sends signals to the thalamus about worrying things. When the caudate neuclus is damaged it fails to suppress minor worry signals and the thalamus is alerted sending signals to the OFC causing a WORRY CIRCUIT

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Family and Twin Studies

80 patients with OCD and 343 of their first degree relatives and compared them with 73 controls without mental illness and 300 of their relatives. Found that people with a first-degree relative who had OCD had 5x greater risk of having it. 

Meta-analysis of 14 twin studies of OCD found MZ twins were twice as likely to develop OCD if their co-twin had the disorder than DZ twins - however, concordance rates are never 100% suggesting that other environmental factors play a role eg. diathesis-stress model

Research support for genes and OFC: Many studies show a genetic link to abnormal levels of neurotransmitters - MRI's used to produce umages of brain activity in OCD patients and their immediate family members without OCD and a group of unrelated healthy people. Findings: OCD patients had less grey matter in key regions of their brain (OFC) - supports genes and OFC 

Real-world application: Parent-to-be may have the COMT gene - can have their eggs screen to give the mother to decide whether to keep the egg. Gene therapy may also be able to turn genes 'off'. However, this is only effective if it is only biological factors that cause OCD

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The Biological Approach to Treating OCD

Anti-depressants (SSRI's): Selective serotonin re-uptake inhibitors increase levels of serotonin to help normalise the 'worry circuit'. Also reduce anxiety that comes with OCD.

Anti-depressants (Tricyclics): Block the transporter mechanism that re-absorbs serotonin and nodrenaline into the pre-synaptic cell after it's fired - they can target more than one neurotransmitter. Have greater side effects so are only used when SSRI's haven't been effective

Anti-anxiety Drugs: Benzodiazepines (BZ's) are used to reduce anxiety - they slow down the activity if the central nervous system by enhancing the activity of the GABA neurotrasmitter which slows down the activity of the neurons in the brain

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Effectiveness: Randomised control trails are used to compare the effectiveness of a drug versus a placebo - 17 studies of the use of SSRI's with OCD patients found them to be more effective that placebos in reducing the symptoms of OCD in the short term - no evidence for the long term

Drug therapies preferred to other treatment: Little effort and time taken than therapies such as CBT. Also cheaper.

Side Effects: Such as headaches, insomnia can make a patient stop taking drugs. Problems with addiction with BZ so usage is limited for 4 weeks

Publication Bias: Exaggeration of benefits of antidepressants - mostly publish positive results and avoid negatives in order to continue te success of their companies 

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Obessions (Cognitive)

Compulsions (Behaviour)

Depression (Emotion)

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