click below
click below
Normal Size Small Size show me how
Psychopathology
OCD- Biological explanation
Term | Definition |
---|---|
COMT gene function | Regulates production of the neurotransmitter DOPAMINE |
COMT gene in OCD | One form/allele of COMT is more common in people with OCD. This form is linked to higher levels of DOPAMINE |
DOPAMINE | A neurotransmitter in the brain, with effects on motivation and "drive". |
SERT gene function | Affects the transport of the neurotransmitter SEROTONIN. Higher levels of serotonin are implicated in OCD. One study found a mutation of this gene where the majority of family members had OCD. SERT gene also linked to other disorders such as Depression. |
Diathesis-stress (genetic explanation) | Link between genes and disorder is not simple. Suggests individual gene creates a vulnerability (diathesis) for e.g. OCD and other factors (stressors) affect what condition develops or IF it does. So could have COMT or SERT variations but no ill effects. |
Gene | Part of a chromosome that carries genetic information in the form of DNA. |
Genetic explanations | link between genetic factors and abnormal levels of neurotransmitters. Explanation suggests that people inherit specific genes that are related to onset of OCD> |
Neurotransmitter | Important chemical substances that transmit nerve impulses across a synapse. |
Neural Explanations (2) | 1. Abnormal levels of Neurotransmitters. 2. Abnormal brain circuits. |
Abnormal levels of neurotransmitters | Dopamine levels thought to be abnormally high in people with OCD- evidence from animal studies. BUT Serotonin low levels are associated with OCD. |
Evidence for low Serotonin levels in OCD | Pigott et al 1990- antidepressant drugs that increase Serotonin activity shown to reduce OCD symptoms. Plus antidepressants that have less effect on Serotonin do not reduce OCD symptoms (Jenicke 1992). |
Abnormal Brain Circuit- which areas of brain are associated with OCD? | Several areas in the FRONTAL LOBES. e.g. CAUDATE NUCLEUS |
The "Worry Circuit" | OFC (Orbitofrontal cortex) sends "worry" signals to Thalamus e.g. germ hazard. These are normally suppressed by the caudate nucleus but when it is damaged doesn't suppress the minor worry signals; thalamus is alerted which then sends signals back to OFC |
Supporting evidence for OFC and worry circuit | Comes from PET scans of patients with OCD, taken when symptoms are active. e.g. hold a dirty cloth if have germ obsession. Scans show heightened activity in OFC. |
Serotonin links to frontal lobes | Serotonin plays a key role in operation of the OFC and caudate nuclei. Abnormal levels of Serotonin might cause these areas to malfunction. |
Evaluation points for Biological Approach to explaining OCD. | 1. Family and twin studies. 2. Tourette's Syndrome and other disorders. 3. Research support for genes and anatomical differences in OFC. 4. Real-world application. 5. Alternative explanations. |
Evaluation Bio approach OCD - 1. family and twin studies - positive | Nestadt et al (2000) found that people with a first-degree relative with OCD had a 5X greater risk than general population. MZ twins X2 more likely to develop OCD if co-twin has the disorder than DZ twins |
Concordance Rate | A measure of genetic similarity. e.g. in twin pairs where one of each pair has a disorder. Concordance rate is number of times the other twin of the pair also has the disorder. |
Evaluation Bio approach OCD- 2. Tourette's syndrome and other disorders | Paul and Leckman studied patients with Tourettes- concluded OCD is one form of expression of same gene that's linked to Tourette's. Supports view that not one specific gene linked to OCD but they act as a predisposing factor towards obsessive behaviour. |
Evaluation Bio approach OCD- 3. Research support | Many studies show genetic link to abnormal levels of neurotransmitters. Menzies et al (2007) MRI images of brain activity in OCD patients and immediate family showed had reduced grey matter in key areas of the brain such as the OFC. |
Evaluation Bio approach OCD- 4. Real-world application | Mapping of human genome has led to hope that specific genes can be linked to particular mental disorders. Gene therapy or embryo testing could then used. However it is unlikely that there is a simple link between genes and OCD. |
Evaluation Bio approach OCD-5. Alternative explanations. | Strong competition from psychological explanations such as two-process model. These explanations are supported by high success rate of Exposure and Response Prevention (ERP) treatment-similar to systematic desensitisation. |
Evaluation Bio approach OCD - 1. family and twin studies -negative | Concordance rates in OCD twin studies are never 100%. This means environmental factors must also play a role (Diathesis-stress model). Also OCD runs in families but specific symptoms (e.g. germ obsession) show must be environmantal influence on symptoms. |