OCD Biological explanations A2
Download as PPTX, PDF9 likes25,313 views
1) The document discusses biological explanations for obsessive-compulsive disorder (OCD), including genetic and neurobiological factors. It notes evidence that OCD may be inherited and research looking at genes like COMT. 2) Neurotransmitters like serotonin and dopamine are also discussed, with lower serotonin and higher dopamine levels found in individuals with OCD. Brain regions implicated include the basal ganglia and orbitofrontal cortex. 3) The orbitofrontal cortex circuit is described, with the idea that damage to areas like the caudate nucleus means "inappropriate impulses" from the orbitofrontal cortex are not properly filtered, leading to obsessive thoughts and compulsive behaviors.
OCD Biological explanations A2
- 2. What are the characteristics of someone with Obsessive-compulsive disorder (OCD)? OCD is an anxiety disorder. The behaviours are ritualistic, (hand washing, constant checking) and is therefore is the source of great anxiety. Interestingly the disorder is equally common in both men and women and the onset of the behaviour is usually in young adult life. Again you could think of the disorder as having two components Obsessions. Compulsions. Obsessions – recurrent, intrusive thoughts or impulses that are perceived as inappropriate, grotesque or forbidden (DSM-IVR). The obsessions generally cause anxiety as they are unlike the sufferers typical thoughts. These thoughts are believed to be uncontrollable, the sufferer feels as though they may lose control and act upon these obsessions. The most common obsessions take the form of DOUBTS Compulsions – Repetitive acts that work to These behaviours can be ‘hidden’ i.e. mental acts or overt i.e. hand washing. The vast majority of sufferers realise their behaviour is irrational but feel compelled to perform the given behaviour for fear of something terrible occurring, thus the behaviour also create anxiety. IMPULSES IMAGES. reduce anxiety of the sufferer by preventing some dreaded event happening (DSM-IVR).
- 3. What are the characteristics of someone with Obsessive-compulsive disorder (OCD)? A diagnosis is given if the sufferer fits the following criteria: Recurrent persistent thoughts, impulses or images that feel intrusive and inappropriate, and cause excessive anxiety or distress. The sufferer partakes in regular repetitive behaviour (hand washing). The behaviour must not be related in anyway to what they are designed to prevent. The individual recognises the behaviour is excessive and product of their own mind.
- 4. 1) Genetic explanations of OCD Predisposition may be inherited. Genetics not as well established as some other biological explanation but search for an ‘anxiety ‘gene’ is underway. Information comes from 3 main sources – family studies, twin studies and newer research methods.
- 5. Genetic explanations of OCD. Support -AO2: Family/Twin Studies- Nestadt et al (2000) 80 patients with OCD & 343 of their near relatives compared with control group without mental illness & their relatives. Strong link with near family (5x greater risk if had first degree relative). Meta-analysis of 14 twin studies found on average MZ twins 2x more likely to develop the disorder than DZ twins. COMT gene COMT helps to reduce the action of dopamine. The variation in the COMT gene decreases the amount of COMT available and therefore dopamine is not controlled and there is probably too much. Researchers collected DNA samples from 73 people with OCD and 148 who did not have a mental disorder. The variation in the gene occurred in nearly half of the men with OCD but only 10% of women with OCD. It was found in about 17% of those with good mental health. .
- 6. Evaluation of genetic factors (AO2) + Concordance rates for twin studies generally high compared with other disorders (e.g.. 87%) + there are a higher number of children with OCD than any other disorder which suggests it might be inherited. +The OCD symptoms of parents and their children are often different which suggests the disorder is not learned. -However, concordance rates are never 100% which means that OCD is not entirely genetic. + COMT gene- study by Schindler confirmed association. -Research rarely replicated as this is a new area +/-Other genes being discovered all the time – unlikely to be just one gene. - Studies before 1990 difficult to interpret due to differences in diagnostic criteria. -Problems with twin studies – they may not be truly identical. Problems with bias in diagnosis. -Difficulties in separating effects of environment and genetics.
- 7. Biochemical Factors (neurotransmitters) (AO1) Serotonin – Lower levels of serotonin found in OCD sufferers . Dopamine levels are thought to be abnormally high in people with OCD- thus suggesting other neurotransmitters are involved in OCD.
- 8. Neurotransmitters These are chemical messengers that transmit nerve impulses from one cell across the synapse (gap) to another cell.
- 9. Link It is thought that serotonin and other neurotransmitters help the functioning of the OFC and caudate nuclei. Seratonin deficiency initiates faulty signals from OCF OFC sends worry signal to thalmus thalmus sends filtered version of danger back caudate nucleus monitors signals
- 11. AO2 Evaluation of biochemical factors +Studies using drugs have shown a reduction in dopamine levels is positively correlated with a reduction in OCD symptoms. +Experiments which inject animals with drugs that increased levels of dopamine have caused the animals to demonstrate OCD type behaviours. +Drugs that increase serotonin (anti depressants) have been shown to reduce OCD symptoms. - But research results relating to serotonin are varied – sometimes symptoms have been made worse. There is a great deal of contradictory research. - Drugs seem to show only partial alleviation of the symptoms so the process is not fully understood. The exact function of neurotransmitters in the development of OCD is far from understood. -Cause or effect- it may be that neurotransmitter levels fluctuate as a result of OCD rather than as a cause of it.
- 12. Neuroanatomy Brain Dysfunction Basal Ganglia –abnormalities in prefrontal cortex where thinking and judgement takes place is often present in OCD sufferers. OCD is often also found in cases of Tourette’s and Parkinson’s disease which are all disorders in which the basal ganglia is implicated. Basal ganglia damage resulting from head injuries can also cause OCD. Surgery which disconnects the basal ganglia from the frontal cortex can reduce symptoms of severe OCD
- 13. Neuroanatomy Brain Dysfunction Another area implicated is the OFC circuit. The OFC sends ‘worry’ signals. These signals are normally suppressed by the caudate nucleus. In OCD the caudate nucleus is thought to be damaged so it cannot suppress the signals which become increasingly excited – increasing compulsive behaviour and anxiety.
- 14. Orbito-frontal cortex and caudate nuclei These parts of the brain form a circuit which converts information into thoughts and action
- 15. Orbito-frontal cortex and caudate nuclei Impulses arising in the OFC are passed to the caudate nuclei, which acts as a filter screening out irrelevant or unimportant impulses. The most powerful ones are passed onto the thalamus. Then the individual is driven to think more about them and to take action
- 16. Orbito-frontal cortex and caudate nuclei Parts of this brain circuit is damaged in people with OCD, so inappropriate impulses get through and they are overwhelmed with troublesome thoughts and actions.
- 18. A02 Evaluation of neuroanatomy explanation Basal ganglia and OFC: +Neuro imaging studies have shown increased activity in basal ganglia in OCD sufferers. - However results of neuro imaging studies have been inconclusive and basal ganglia impairment has not been found in all OCD patients. + Scans show increased activity in OFC in OCD patients. + It has been demonstrated that OFC damage caused by head injury, viruses and tumours can give rise to OCD. + Menzies (2007) supported both neuroanatomical and genetic explanations – make notes on the study (207)
- 19. Evaluation of biological explanations Promising research but cannot yet offer a complete explanation. One of most powerful challenges to this view is that PSYCHOLOGICAL interventions show a strong therapeutic effect and yet do not rely on drugs or make any physical intervention.
- 20. Examination questions on biological explanations: January 2010 Outline one biological and one psychological explanation for obsessive compulsive disorder (9) Evaluate explanations for obsessive compulsive disorder (16) June 2010 Not examined -Psychological therapies and clinical characteristics January 2011 June 2011 January 2012
- 21. Psychological explanations of OCD Psychodynamic Freud –OCD arises when unacceptable wishes and impulses from the ID are only partially repressed and so provoke anxiety. The use of ego defence mechanisms reduce the anxiety. The 3 most common defences in terms of OCD are: isolation ( people attempt to isolate themselves, or disown undesirable thoughts and impulses. When the forces of the ID dominate, the impulses intrude as obsessional thoughts. undoing ( when isolation fails the second defence of ‘undoing’ produces compulsive acts-washing away unacceptable impulses) reaction formation (taking on traits that are opposite to the unacceptable impulses-such as compulsive kindness may be a way of countering unacceptable aggressive impulses.)
- 22. Psychodynamic-Adler Inferiority complex explanation Some parents dominate their children and prevent them from developing a sense of their own competence. When this happens an inferiority complex may result so that later, as adults, these people may adopt compulsive rituals such as tidying out drawers, in order to carve out an area in which they exert control of something and can feel competent.
- 23. Psychological explanations of OCD + Freud used the evidence of Rat Man to support his explanations - Some researchers have suggested that the therapy developed by Freud (Psychoanalysis) may have a negative effect on OCD recovery. - -Difficult to test the idea of unconscious motivations. No convincing evidence to support the PD view of OCD and psychoanalysis has been of little help in helping people to overcome OCD.
- 24. Psychological explanations of OCD. Behavioural Mowrer suggested that the learning of fears is a two step process: Classical conditioning A neutral stimulus becomes associated with anxiety through Classical Conditioning. Operant conditioning Any action that enables the individual to avoid a negative event is negative reinforcement. Avoidance of the fear leads to positive outcomes and is therefore reinforced. Thus the compulsive behaviour becomes a way of establishing control and reducing anxiety- and as a result the behaviour is reinforced and the behaviour may become compulsive whenever the individuals face thoughts that provoke anxiety.
- 25. Psychological explanations of OCD. Behavioural evaluation AO2 + Researchers thought that if Mowrer was right, that OCD patients are predisposed to more rapid conditioning. Research did support this finding, OCD patients were conditioned more rapidly. +Further research (Rachman) has shown that compulsions do relieve the anxiety of obsessional thoughts. In a series of experiments OCD patients were asked to carry out some ‘prohibited’ activity such as touching something dirty. Patients were then allowed to carry out their compulsion (showed reduction in anxiety). If however they were asked to delay carrying out their compulsive activity their anxiety levels were found to persist for a while then gradually decline. Compulsions therefore provide a quicker relief from anxiety. + This theory has led to development of a reasonably effective therapy –ERP. - Theory does not explain the CAUSE of the obsessive thoughts, it explains how they are maintained. (e.g. aspirins might cure headaches but headaches are not due to lack of aspirin in the body!)
- 26. Cognitive explanations of OCD Cognitive: Everyone has unwanted or intrusive thoughts from time to time but these thoughts can be ignored or dismissed fairly easily. For some people irrational thoughts cannot be ignored and feel overwhelming leading to the expectation that terrible things will happen. The thoughts continue because the person cannot ignore them. This is also because they often have depression. In order to avoid the consequences of these thoughts the sufferer must ‘neutralise’ them. This only provides temporary relief and then the anxiety builds up again. Over time people become more convinced that these thoughts are dangerous and they become obsessions. The need to reduce the anxiety they cause becomes a compulsion.
- 27. Evaluation of cognitive explanations of OCD + Research has supported the idea that people with OCD have different patterns of thinking, such as believing that they should have total control over their world. +Research has also shown that people with OCD have more intrusive thoughts than ‘normal’ people. +The Rachman research also supports the cognitive explanation as well as the behavioural explanation. + CBT therapies have been shown to be reasonably effective in treating OCD. -the theory is more descriptive than explanatory – why do people develop OCD in the first place? We all have intrusive thoughts but don’t all get OCD.
- 28. Conclusion No single explanation can account for a complex disorder like OCD Likely to be an interaction between biological, psychological and social factors. Diathesis stress model- certain individuals have an underlying biological predisposition to OCD. This may develop fully in response to environmental triggers.