1. Sleepwalking By Sunne, Sam, Caitlin and Felix

2. The theory A diathesis-stress model recognises that there are predisposing factors (the diathesis) and environmental causes to a disorder (the stress). It is important to realise that sleepwalking occurs in SWS. This model of sleepwalking says that there is a genetic predisposition to sleep walking, which is the diathesis; this genetic predisposition is likely to be incomplete arousal – so people’s genes predispose them to be in this state, which is a state between sleep and wakefulness. Sleepwalking occurs in SWS and typical EEG recordings taken during sleepwalking show delta waves typical of SWS plus higher frequency beta waves which are characteristic of an awake state. Hence it appears that sleepwalking occurs when the person in SWS is awakened but the arousal of the brain is incomplete so they still appear asleep. The stress part of the model is two fold: 1) maturation of key neural circuits in the brain; when the circuits mature sleepwalking stops, which is why most people grow out of sleepwalking 2) factors that increase the amount of SWS that is experienced and so increase the chance of sleepwalking occurring. These factors include sleep deprivation, drinking alcohol, fever and being a child.

3. Research evidence Bassetti: - Volunteer sample, 16 were genetically tested. 8 (50%) participants had a particular form of the HLA gene suspected of making people more susceptible to sleepwalking supporting the theory’s proposal of a genetic predisposition to sleepwalking. This form of gene was found in 25% of the non-sleepwalking population, however it should be noted that not everyone who sleepwalks is aware of it. Zadra: 15+ year review of sleepwalking cases found that 45% of sleepwalkers had daytime sleepiness, supporting the idea put forward by the theory that the brain is in a state of incomplete arousal as they do not appear to be completely asleep but in a state between asleep and awake; they’re not actually asleep they just appear to be. 80% of sleepwalkers had a family history of sleeping disorders supporting the idea of a genetic or biological link. Ohayon, Mahowald, Dauvillers, Krystal, Lëger: found 30% of those who sleepwalked had a family member who also experienced sleepwalking. Gurnett: found a particular section of DNA on chromosome 20 that is inherited by sleepwalkers.

4. Evaluation of research evidence All the above studies use highly scientific methodology, such as genetic testing, thus increasing objectivity as reliable test are conducted and it is free from biases that occur with more qualitative methodologies, such as researcher bias that occur through having to interpret results thus research is not value free. Additionally, all the studies are consistent in their findings towards a genetic link therefore increasing the reliability in their support for the diathesis-stress model of sleepwalking, however none of them investigate slow wave sleep, how the environment can increase the likelihood of sleepwalking, or why it is more likely to occur in children, thus not fully supporting the theory. These studies are much more strongly supporting the biological side of the diathesis-stress model.

5. IDA A relevant issue to discuss here is the nature/nurture debate. The nature side of the theory argues there is a genetic predisposition to sleepwalking which is likely to be due to incomplete arousal – a state between wakefulness and sleep. On the other side of the argument, it looks at the role of nurture and the environment. As we get older (an external factor) our neural circuits mature and the interaction between nature and nurture cause sleepwalking as the environmental factors further increase the likelihood of sleepwalking as the environmental factors further increase the likelihood of sleepwalking if someone is predisposed. The role of nurture here is positive as it suggests the possibility of treatments. If the individual’s sleepwalking is severe, it can be easily prevented by removing the environmental triggers such as alcohol.

6. Wider evaluation The theory doesn’t explain how or why incomplete arousal occurs, or why only some people experience it. Therefore, this could be considered more of a description of what happens in sleepwalking, rather than an explanation of why it occurs. It has been suggested that this is why there are no specific treatments for severe sleepwalking at this time, however many things can be recommended such as: Regular bed times – the routine helps people to relax Reduce alcohol consumption Get more sleep as it has been found that sleep deprived people sleepwalk much more often.