Delusional but nevertheless, held by an individual who believes

Delusional disorder is a clinically classified psychotic disorder whereby delusions are the most prominent symptom. However, delusions can also occur as observable psychotic symptoms as part of particular medical or neurological disorders such as schizophrenia, dementia, shared psychotic disorder, and amnesia amongst others. To measure how prone individuals are to delusional thoughts, the Peters Delusions Inventory can be used. This inventory asks participants whether or not they have ever experienced various different beliefs that often occur within a clinical context. The results in a delusion-proneness range from 0 to 21. Among the general population, individuals typically score an average of 6.7 with no reported difference between genders, and those with psychotic delusions generally score an average of twice that amount (Peters, 1999). Delusions are typically described as irrational, preoccupying and often bizarre beliefs that are evidently false but nevertheless, held by an individual who believes them to be true and completely absolute (Bortolotti, 2010). Furthermore, delusions are wholly idiosyncratic meaning that the beliefs held by the affected individual are not shared by others, nor are the beliefs accounted for by the affected individual’s culture, religious background or their level of intelligence (Kiran et al, 2009). Consequently, whilst religious beliefs and common conspiracy theories may be arguably false, as they are considered to be true by a vast amount of the world’s general population, they are therefore not considered to be delusions (Ross & McKay, 2017). However, some individuals can experience delusions related to these widely held beliefs and yet, their own personal beliefs are still considered to be false and fall under the category of delusional thinking. For example, the Messiah Complex, which is often reported in patients suffering from bipolar disorder and schizophrenia, is when an individual holds the belief that they are some kind of deity or destined to become one (Goldwert, 1993). Jaspers (1963) suggested that there are four types of primary delusions which are delusions that do not occur as a response to another stimuli such as mood disorder. Primary delusions include: delusional atmosphere, delusional perception, delusional ideas and delusional awareness. This suggestion provides some insight into how multifaceted a disorder with delusions may be, and how complex delusions themselves can be whilst affecting both clinically diagnosed and also “healthy” individuals. Blakemore et al (1998; 2000) sought to explain how healthy individuals could not engage in some of the behaviours that clinically delusional patients could. For example, it was found that there was a reduction in sensation when “healthy” individuals self-produced a tickle sensation (i.e., tickled themselves). Therefore, the consensus was that “healthy” individuals could not tickle themselves. It was suggested by Blakemore et al. (1998) that the reason for this reduction in sensation was due to sensory predictions during the action whereby the internal forward model in the motor system predicts sensory consequences of one’s movement based on the motor commands made. Therefore, when a movement is self-produced (e.g., individuals tickling themselves), its sensory consequences can be predicted by the forward model and this reduces the sensory effects. In contrast, externally generated sensations are not associated with any efference copy and therefore cannot be predicted by the forward model so the individual could feel a tickle sensation if it is externally produced. This sensory reduction (i.e., no tickliness), also referred to as the cancellation hypothesis, may be controlled by the somatosensory cortex and the anterior cingulate cortex which is a significant part in the processing of top-down and bottom-up stimuli, and also assigning appropriate control to other areas in the brain (Blakemore et al, 1998). It was suggested that this predictive mechanism that allows for sensory reduction may be faulty in patients with auditory hallucinations or passivity experiences. The cancellation hypothesis may also explain why sounds one self-generates are perceived to be quieter than external sounds as found by Weiss et al (2011) who tested the assumption that the experience of generating and controlling one’s actions are closely linked to internal motor signals associated with the ongoing actions by comparing sensory attenuation of self-generated and observed sensory effects. Specifically, the study compared the loudness perception of sounds that were either self-generated, generated by another person or a computer. As concluded by Weiss, it remains to be investigated whether sensory attenuation would only be determined by this specific interplay or whether it may be modulated by other factors related to the capacity of the individual to act independently. Whilst it has been found that healthy individuals cannot tickle themselves, a later study by Blakemore et al. (2000) found that those who are clinically delusional can. The results from the study support the proposal that auditory hallucinations and passivity experiences are associated with an abnormality in the forward model mechanism (Frith et al, 2000; Wilkinson, 2015) that normally allows us to distinguish self-produced from externally produced sensations. It is possible that the neural system associated with this mechanism, or part of it, operates abnormally in individuals with such symptoms. Moreover, it has been found that this predictive mechanism is not common in patients with auditory hallucinations or passivity experiences also known as delusions of control. This symptom occurs when an individual experiences his or her will as replaced by that of some other force or agency (Mellor, 1970; Lindner et al, 2005; Shergill et al, 2004). Although delusions may be the most visibly present in psychotic conditions, delusional thinking is also possible in nonclinical, “healthy” groups who do not present with other symptoms that would be typical of a delusional disorder. Approximately 1 to 3 percent of the nonclinical population have delusions of a level of severity comparable to clinical cases of psychosis. A further 5 to 6 percent of the nonclinical population have been reported as holding delusional beliefs, but not of such severity (Freedman, 2006). One example of “healthy” individuals showing symptoms of psychosis-like delusions can be found in a study by Pechey and Halligan (2010) whereby 1000 participants were presented with 17 delusional-like beliefs and asked whether they held them strongly, moderately, weakly, or not at all. The non-bizarre beliefs included: whether others were out to harm the individual, and then more bizarre beliefs such as whether the individual was dead or alive in that particular moment. It was found that 39 percent of participants held at least one of these beliefs strongly, and 91 percent held one or more at least weakly.

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