For example: a man claiming that he flew into the Sun and flew back home. This would be considered a delusion, unless he were speaking figuratively, or if the belief had a cultural or religious source. Only the first three criteria remain cornerstornes of the current definition of a delusion in the DSM-5. Robert Trivers writes that delusion is a discrepancy in relation to objective reality, but with a firm conviction in reality of delusional ideas, which is manifested in the "affective basis of delusion." Treatment
Delusions and other positive symptoms of psychosis are often treated with antipsychotic medication, which exert a medium effect size according to meta-analytic evidence. Cognitive behavioral therapy (CBT) improves delusions relative to control conditions according to a meta-analysis. A meta-analysis of 43 studies reported that metacognitive training (MCT) reduces delusions at a medium to large effect size relative to control conditions. Criticism
Some psychiatrists criticize the practice of defining one and the same belief as normal in one culture and pathological in another culture for cultural essentialism. They argue that it is not justified to assume that culture can be simplified to a few traceable, distinguishable and statistically quantifiable factors and that everything outside those factors must be biological since cultural influences are mixed, including not only parents and teachers but also peers, friends, and media, and the same cultural influence can have different effects depending on earlier cultural influences.
The volume of the hippocampus and parahippocampus is related to paranoid delusions in Alzheimers disease, and has been reported to be abnormal post mortem in one person with delusions. Capgras delusions have been associated with occipito-temporal damage and may be related to failure to elicit normal emotions or memories in response to faces. Diagnosis
The modern definition and Jaspers original criteria have been criticised, as counter-examples can be shown for every defining feature. Studies on psychiatric patients show that delusions vary in intensity and conviction over time, which suggests that certainty and incorrigibility are not necessary components of a delusional belief.Delusions do not necessarily have to be false or incorrect inferences about external reality. Some religious or spiritual beliefs by their nature may not be falsifiable, and hence cannot be described as false or incorrect, no matter whether the person holding these beliefs was diagnosed as delusional or not. In other situations the delusion may turn out to be true belief. For example, in delusional jealousy, where a person believes that their partner is being unfaithful (and may even follow them into the bathroom believing them to be seeing their lover even during the briefest of partings), it may actually be true that the partner is having sexual relations with another person. In this case, the delusion does not cease to be a delusion because the content later turns out to be verified as true or the partner actually chose to engage in the behavior of which they were being accused.