Biological Explanations of OCD Unit 1 - Psychopathology Biological Explanations of OCD

Explanations of Abnormality Biological Approach Abnormality is an illness or disease caused by: Genetics Neural Explanations Brain Structure (Neuroanatomy) Biochemistry (Neurochemistry) Infection (less important)

Why are researchers interested in twins? DZ Twins Diazygotic = 2 sperm/eggs Share 50% of their genes MZ Twins Monozygotic = 1 sperm/egg divides Share 100% of their genes Why are researchers interested in twins?

Biological Explanations Genes Schizophrenia – genetic relatedness General population = 1% risk 1st degree relative (son/daughter) = 10% risk DZ twins = 17% risk MZ twins = 48% risk

Biological Explanations Brain Structure/Neuroanatomy

Brain Function

Abnormal temporal lobes

Biological Explanations Biochemistry Depression linked with serotonin Schizophrenia linked with dopamine

OCD - Recap What are the behavioural, emotional and cognitive characteristics of OCD? C-A-R R A D I O

OCD – CAR RADDIO Compulsions-Anxiety Reducing and Repetitive Avoidance Depression Distress Insight Obsessive thoughts http://estream.bhasvic.internal/view2.aspx?id=7953~4y~AqgxJUFe

Characteristics of OCD OCD is an anxiety disorder where sufferers experience persistent and intrusive thoughts occurring as obsessions, compulsions or a combination of both. Obsessions tend to be things people think about, which lead to feelings of extreme anxiety. They comprise forbidden or inappropriate ideas and visual images that aren’t based in reality e.g. being convinced that germs are everywhere. Compulsions are what people do as a result of the obsessions. They comprise intense, uncontrollable urges to repetitively perform tasks and behaviours e.g. obsessively washing hands to remove germs. The compulsions are carried out in order to reduce distress or prevent feared events. Most sufferers realise their obsessive ideas and compulsions are excessive and inappropriate, but cannot consciously control them, resulting in even higher anxiety. They also appreciate their compulsions are only temporary solutions. A sufferer’s obsessions and compulsions become very time-consuming, thus interfering with the ability to conduct everyday activities.

Group work Genetic Explanations Neural Explanations One person outlines explanation One person evaluates explanation Neural Explanations Check your summary with me; then teach it to the other four in your group. Do not just copy the booklet word for word!

Starter question

Recap - True of False? The genetic explanation to OCD is part of the cognitive approach. The genetic explanation looks at if individuals inherit a genetic disposition to developing OCD. Genetic disposition means that OCD could be caught like an infection or a cold. An example of your first degree relatives would be your grandad or uncle. A family study by Nestadt found concordance rates of 11.7% for first degree relatives compared to 2.7% in the control group. A concordance rate is the probability that a pair of individuals will both have for e.g. OCD, given that one of the pair already has OCD. The concordance rate found by Carey (1981) for MZ twins suffering obsessive symptoms was 100% compared to 0% for DZ. OCD is polygentic and it is thought that there may be up to 230 genes involved in its cause.

Recap - True of false The genetic explanation to OCD is part of the cognitive approach. False -Biological The genetic explanation looks at if individuals inherit a genetic disposition to developing OCD. True Genetic disposition means that OCD could be caught like an infection or a cold. False - A weakness is passed down in your genes from your parents An example of your first degree relatives would be your grandad or uncle. False -mum, dad, brother, sister A family study by Nestadt found concordance rates of 11.7% for first degree relatives compared to 2.7% in the control group. A concordance rate is the probability that a pair of individuals will both have for e.g. OCD, given that one of the pair already has OCD. The concordance rate found by Carey (1981) for MZ twins suffering obsessive symptoms was 100% compared to 0% for DZ. False - MZ 87%, DZ 47% OCD is polygentic and it is thought that there may be up to 230 genes involved in its cause.

Predisposition to OCD is inherited. Genetic Explanations Predisposition to OCD is inherited. Do you agree?? Family studies (Nestadt et al, 2000) and twin studies (Carey and Gottesman, 1981) Studies on families and twins have both found a link between genetics and OCD however we have not reached any firm conclusions about genes being the actual cause of OCD. OCD seems to be ‘polygenic’ – what does this mean? ‘Poly’ - many ‘genic’ – genes …so NOT just 1 gene Taylor (2013) found evidence that up to 230 different genes may be involved in OCD. BUT…Cromer et al (2007) found a traumatic past event in +50% cases of OCD

What role do genes play in the development of OCD The diathesis-stress model suggests that certain genes leave some people more likely to suffer a mental disorder but some environmental stress or experience is necessary to trigger the condition.

Neural explanations of OCD: Neurotransmitters and areas of the brain Neurotransmitters are brain chemicals that relay signals from one neuron (nerve cells) to another Serotonin is thought to be associated with regulating mood and anxiety (OCD is an anxiety disorder) Low levels of serotonin have been found to be associated with OCD and is thought to be linked to obsessive thoughts.

Biochemical explanation What bio-chemical is linked to OCD? Is it high or low levels that increase your risk of OCD? How is this linked to mood?

Biochemical explanation What bio-chemical is linked to OCD? Serotonin Is it high or low levels that increase your risk of OCD? Low How is this linked to mood? Normal passing on (transmission) of mood-relevant info does not take place so mood and mental processes are effected, i.e. OCD.

Nueroanatomy Orbitofrontal cortex-This is found in the prefrontal cortex just behind the eyes and is part of a brain circuit. Its main job is to turn sensory info into thoughts and actions. Basal ganglia- It is thought to be linked to the pre-frontal cortex and the caudate nucleus in located within it. Patients who suffer head injuries in this region often develop OCD-like symptoms, following their recovery. Caudate nucleus-Located in the basal ganglia- regulates the messages from the OFC to the thalamus, stopping the thalamus from getting excited if not necessary. Thalamus-This gets excited if it receives messages from the OFC via the caudate nucleus and then carries out action and sends info back to the OFC.

Neuroanatomy The orbital-frontal cortex (OFC) is the part of the brain that notices when something is wrong. For example, when the OFC registers that there is dirt nearby, it sends a 'worry' signal to the thalamus. The thalamus directs signals from many parts of the brain to places that can interpret them - in this case back to the OFC. These nerve cell connections form a loop in the brain. The caudate nucleus lies between the OFC and the thalamus and regulates signals sent between them. When the thalamus receives a 'worry' signal, it becomes excited and sends strong signals back through the loop to the OFC, which interprets them. Normally, the head of the caudate nucleus acts like the brake pedal on a car, suppressing the original 'worry' signals sent by the OFC to the thalamus. This prevents the thalamus from becoming hyperactive. But in OCD, the caudate nucleus is thought to be damaged, so it cannot suppress signals from the OFC, allowing the thalamus to become over-excited. If this occurs, the thalamus sends strong signals back to the OFC, which responds by increasing compulsive behaviour and anxiety. This could explain the repetitive and seemingly senseless rituals performed by obsessive-compulsives REF: http://www.bbc.co.uk/science/humanbody/mind/articles/disorders/causesofocd.shtml

Brain of an OCD sufferer and non sufferer-what can you see?

Activity So the Orbitofrontal cortex, caudate, nucleus and thalamus create a kind of circuit. Fill in the gaps to create a flow diagram of how a “normal” and an OCD brain would work after walking past someone with a slight cold.

Activity Circuit ended Caudate nucleus decides isn’t a problem Orbitofrontal cortex sends a message of panic Caudate nucleus decides isn’t a problem supresses signals from OFC Circuit ended

Activity Orbitofrontal cortex sends a message of panic Caudate nucleus (is faulty) Can’t supress signals from OFC so passes info on Thalamus receives message of panic and gets excited carries out the action Wash hands and face 5 times with disinfectant

Supporting Evidence Evaluate these findings on MWBs…

Evaluation of Neural Explanations

Testing your knowledge You have 7 minutes to answer the following exam question Outline one neural explanation of OCD (4 marks) Use the structure below to scaffold your answer -One sentence about PET scans and the area of the brain they found had higher activity for OCD patients. -One sentence about what the OFC does -Explain the circuit for a non OCD sufferer -Explain the circuit for someone with OCD -Make sure you mention how the loop keeps repeating which explains why compulsions are repetitive rituals. Need a hand? Use the blue and yellow cards and your flow diagram but NO PACKS! Finish before the 7 minutes? Have a go at this challenge question Give one limitation of the genetic explanation to OCD (3 marks).

Swop your answer with somebody else 0- no relevant information 1- only mentions one of the points in the scaffold 2- Mentions two of two of the point 3- Mentions 3 of the points and clearly explained 4- The answer is clear, well written and mentions all of the points in the scaffold

Starter question