Delusions are associated with individual psychological differences, with there being evidence that the information we learn culturally is filtered by our individual biases. If a person has several hypotheses they must choose from, their responses may be available to others. Also, it seems that the harder a category is to learn, the more data and time is needed for learning. And the less likely it is to be considered in the first place and as the generations pass the less likely we are to see it represented, i.e., concepts with higher probability are more easily learnt and get passed. Also, as an aside, some generations seem to choose hypotheses that are far from the most probable, which links into the topic of creativity (Griffiths 2008).

 

Could the above reasoning influence the development and transmission of delusions? If we consider folie a deux, the secondarily affected delusional patient will have chosen an explanation based on the delusions of the primary case. If the probability of a hypothesis chosen by the delusional person is low, would it be harder to learn by others and hence less likely to be passed on? This would fit in with the low frequency of folie delusions. So is the social transmission of delusions the defining feature of folie delusions, whereas the lack of transmission a reflection of other delusional types? The trouble here is that others may well believe in non-folie delusions. So could folie delusions represent a subset of ‘transmitted’ delusions as opposed to simply being a collection of features that just happen to be interesting to some people? Could the conditional probability that a delusion is true given the data serve as an indicator of ‘cultural reality’? In that the delusions represent ‘reality’ as filtered by cultural norms and evolutionary priorities, and hence those delusions with a low probability represent ‘unreality’ and hence be discarded. If the process of determining probabilities is altered, than low probability hypotheses may be perceived as having a higher probability of occurrence.

 

Our conscious experiences, e.g. emotions and nervous, interact together and we may respond to a set of meaningful collective experiences, as recognised by the community. These experiences will vary with culture and time and may even have their own representations neurologically. So, delusions occur within these experiences and to fully understand them we need to understand what they mean in the local culture. This of course says that delusions cannot be fully understood from a neurological or psychological point of view (Turner 2008).

 

Now there is evidence that our visual system is altered in delusions, specifically assessed by the Visual Scan Path technique (see later) and there is evidence that the culture in which we grew up can alter visual perception. By using the Frame Line Test, participants are presented with a square with a vertical line in it and they then must draw the line, either to the same length (so ignoring context) or to draw it in relation to the box (so using context). Those in western countries where individualism is favoured tend to do better with drawing the line to the correct length but not so good with drawing a line in relation to the box, while those in eastern countries where collectivism is favoured show the opposite pattern; so cultural context has altered the visual perception of the line and the box. This brings into question the cross-cultural validity of neuroscientific data in the study of delusions (Chiao 2008).

 

Evolution has been described as the transfer of information, e.g. protein structure, behavioural techniques, etc. (Jablonka 2005). This information transfer will result in changes to genes and phenotype as time goes by. Could we apply this concept of information to delusions? If so than what kind of information is being transmitted? So, let’s speculate possible functions of the different types of delusions.

 

• Paranoia: Humans come across aggressive situations that we must deal with. Those who are successful in aggressive situations may be more likely to survive than those who are not successful at such behaviours. Possible functions fulfilled could be:

  1. Natural selection as they survive

  2. Sexual selection as they are around to mate

  3. Kinship via providing protection and resources

  4. Pathogen avoidance by removing infected people

 

1. Delusional jealousy: This might increase the chances of getting and keeping a mate and hence having children, i.e. sexual selection.

 

• Somatic: Here the person is now reacting to events they perceive are occurring within their own body. The resultant illness behaviour might have the following functions:

  1. Lead to some form of help from the group, enhancing natural selection

  2. Protection from pathogens

  3. Does it provide advertisement of fitness, hence helping sexual selection?

 

1. Erotomania: this has an obvious role via sexual selection.

 

1. Grandiose: This is where people display high levels of euphoria, happiness, elation, etc. We generally like to be around the company of happy people, maybe such people are more generous.

 

1. First rank delusional symptoms: This involves alteration of where we define the self and not-self. What possible functional role could this have? Does it help assimilate into other cultures by taking on some of their values? Would it be involved in trances and the like, which are part of ancient medical systems and connecting with the ancestors, etc allowing for social function?

 

1. Other: In clinical practise we often see delusions with contents that do not fit neatly into the above categories.

   1. Homosexuality – there are patients who are convinced that others view them as a homosexual.

   2. Pregnancy – this is where people feel that they are pregnant.

   3. Zoomorphism – this is where people feel that they have been transformed into animals.

   4. Delusional perception – this is where a normal perception is imbued with a delusional meaning.

   5. Delusional mood – where an individual feels something significant is happening.

 

Developing delusional behaviours may be modulated by the probability of learning cultural values. If delusions are primarily cultural constructs, then the prevalence of delusions would reflect the probability that people believe the delusional construct. If delusions are primarily evolutionarily based, then we would expect to see long-term changes in frequencies of delusions as natural selection occurs. One aspect of behavioural-genetic coevolution is that we construct habitats that are suitable for us: ‘niche construction’. I wonder if there is something akin to this in the psychological realm. I presume that this would reduce distress/discomfort, etc. Could delusions be a result of a process to achieve relief? Niche construction can involve a manipulation of space, changing the spatial environment which then serves to provide further input and feedback. It may result in the environment/perception/cognitive processing being simplified via the formation of categories and these than inform further thought, etc. Some have suggested that niche construction would alter environments for succeeding generations, who would then make their own changes, and these constantly changing environments would impact on genetic evolution, e.g. we learn cognitive abilities by observation (Wheeler 2008). A cultural change may lead people to behave in certain ways and as time goes by cultural views may encourage genetic changes that allow these features to appear more easily. So that in time it becomes easier to fit into the culture. Now not all behavioural or cultural changes are adaptive, and some may die out as they are not propagated. While others that fit in are propagated and learned by future generations, for example distress caused by fashions, etc. lead men and women to desire a body image that is different to the one they have or not healthy and this may reach delusional proportions. Could a malleable body image help people fit in better with prevailing cultural norms? Could the desire to be thin (females) and muscular (men) be an example of a maladaptive cultural norm, that if it persisted for long enough, would result in genetic changes favouring thinness in females and muscularity in males? (Jablonka 2005)

 

So could delusions be in part due to a consideration of various alternatives, each with different probabilities of occurrence? When possibilities are considered we see a stage where the probabilities are updated, maybe via the formation of cognitive structures, etc. that then form a new set of inputs that serve to further alter the probabilities of occurrence. This would then eventually result in some outcomes being deemed more probable. The information processing differences that are found in the delusional may serve to bias the whole developmental processes onto an ‘illness’ pathway, with some of this bias coming from the formation of abnormal cognitive structures. This can occur within the individual, resulting in the delusions, or between individuals. If the people around the delusional person do not have any information processing bias, then presumably they would evaluate culturally relevant information in a way where the updated probabilities form cognitive structures that guide further evaluation along a more culturally relevant path.

 

Current criterion says that a delusion is not in keeping with cultural background. This means that social norms can decide what is a delusion, but this works against novel ideas from people who challenge the status quo. Some have claimed that delusional patients being unable to convince others of the truth of their delusions, distinguishes them from normality, but this becomes a circular argument as we as professionals deliberately do not allow ourselves to be influenced. How can a psychiatrist know the patient and their background and decide that something is delusional using their own experiences as a guide (Boyle 2002).

 

This cultural view of delusions may say something about computer and internet-related delusions appearing recently. There are online communities relating to mental health, e.g. mind control, providing a space for like-minded people, with some describing their delusions in terms of transmitters, chips and radiation. One case felt that he was a character in a computer game (Forsyth 2001). A 27-year-old male felt that his life was controlled by the internet (Tan 1997). In India a 31-year-old male felt his sister-in-law was controlling him via the internet and computer. With belief modification, as he had no concept of how the internet and computers worked, the belief had gone in about three weeks. The authors felt that ignorance and fear of new technology caused the delusion (Harpreet 2002). In general, some feel that this is a new type of delusion, others that it is an expression of cultural changes (Lerner 2006). Do these delusions come in the form we expect of delusions? With the content simply being filled in by the brain (Bell 2005).

 

Social failure - A fascinating account of delusions views them as adaptive social mechanisms to combat social failures, which can be so damaging that some people use self-deception to tackle them. Interestingly anosognosia, where people deny their disability, may be associated with people who use denial regularly as part of their premorbid personality (Heilman 1998). This loss of function would be a source of social failure and potentially grounds for delusional behaviour designed to regain social resources.

 

Low self-esteem - It has been suggested that delusions, especially paranoid delusions, protect against the development of low self-esteem. One study found that as conviction drops with CBT, the scores on Beck’s Depression Inventory also drop (Chadwick 1994). The delusional may have improved self-esteem, as sense is made of the environment (Sims 1993). The actively delusional had lower covert self-esteem but there was no difference in overt self-esteem, supporting the view that persecutory delusions help to maintain self-esteem (McKay 2007). Delusional patients make external attributions for negative events, presumably to avoid conflicts within themselves, but this is also found in the general population (Bruce 1999).

 

Let’s consider hypochondriacal/somatic delusions. The person develops symptoms which they think are due to physical illness; they then present to physicians, who then proceed to do physical examinations and tests to find an explanation. This can reinforce the notion that there is a physical disorder. But when no physical disorder is found, this can frustrate the patient and may lead to greater health-seeking behaviour. This can lead to an angry patient who can’t understand their symptoms and frustrated doctors who can’t find any explanations. Hence a psychiatric referral is made, which is often resented by the patient and the anxiety, shame, depression, constant preoccupation, interruption to normal social processes, etc. can lead to a pre-delusional state. The stronger we identify with illness, the more likely we are to suffer some detriment, and this leads us to experience a range of psychological problems, such as denial, etc. We all have a certain concept of illness, against which we review a vast array of psychosocial features, and it is the result that we take to the health professional. This professional socially interacts with the patient and comes to a decision about diagnosis, treatment, etc. But the illness behaviour needs to be understood from the personal point of view (e.g., consequences, functional changes, changes to others, etc.), from a familial point of view as family influences development of illness behaviour, and from a wider social perspective (on what symptoms are acceptable, what others feel is proper behaviour). Could this explain the development of somatic delusions? (Sims 1993)

 

Could we look at delusions in a more functional way? Let’s stay with illness behaviour. Today with proper medical care, illness behaviour has become more adaptive, as we are more likely to get relief from suffering. So, is there now a different reason why illness behaviour is adaptive today, as opposed to that which were more prominent in the past? Because in our evolutionary past, health care was presumably rudimentary, eliciting help to deal with health issues may have gained greater prominence as modern medicine developed, masking other functions of illness behaviour somewhat. Stigmatisation would have raised the inclusive fitness of those doing the stigmatising by avoiding those who are disordered in some way, but it is conceivable that other evolutionary processes may have operated to prevent this reduction in fitness potential. Stabilisation of social groupings may occur with illness behaviour, in that those with similar problems join into a more accepting social group. How would this stabilisation have appeared, reduced intra-group conflict, or provided learning for other members of the group to avoid a similar fate? The question then arises of how someone who is highly convinced, distressed, etc. by the illness behaviour, could have an enhanced inclusive fitness. This social stabilisation has been reflected in some ancient systems of health care and, even today, there are some who feel medicine helps to provide a degree of social control, which is most obvious when professionals and patients disagree.

 

Finally, when it comes to the data I collected, I searched CKN, google scholar, pubmed, medline and manually searched print journals for various variables on the different delusional types. More details will be found in each section, but I would collect data on age, gender, marital status, employment status, presence of a medical history, presence of a psychiatric history, a family history of psychiatric illness, presence of psychiatric treatment and the response to such treatment, the presence of other delusional types, presence of hallucinations, the number of children and the binary presence of children, the number of siblings, and the duration of the delusions.

 

As part of this process, this volume reviews many studies, with differing methodologies, statistical approaches, etc. As a result, they cannot be directly compared and hence I have not tried to do so. Such shortcomings essentially mean that this volume is mainly a hypothesis-generating text. I have focused on searching the literature for case reviews, as it provides data on individual level differences and by building up as a large a dataset as possible, it may increase the power to detect possible influences. This of course does not mean that I haven’t tried to extract usable data from various clinical studies, supplemented by the result of other authors’ meta-analysis and systemic reviews. Other problems include the fact that delusional content is poorly described, the differences between delusional patients are not highlighted, social circumstances are not explicitly investigated, various rating scales are used in studies, as are different definitions of a delusion and small sample sizes limit generalisability. Content may indicate different neuropathology and often confounders such as other illnesses, medications, duration of psychotropics, etc., are not controlled for.

 

Data for dichotomous variables were labelled ‘0’ to indicate absence and ‘1’ to indicate the presence of said variable. When data on the variables were missing from the case reports, I assumed an absence of that variable, e.g., if no information was listed on marital status, I assumed the person was single. When it came missing values, I used STATA multiple imputation commands. I calculated simple descriptive statistical results, such as means, medians, etc, before moving to bivariate analysis such as correlations. Finally, I moved on to simple and then multiple regression methods. Depending on the levels to the dependant variable, I would either use normal regression, logistic or ordinal regression methods.

 

When it comes to mathematical analysis, several methods will be used and they will be described as and when relevant studies are posted online. For example, multiple regression analyses were performed on the datasets looking at the general direction of the regression coefficients, as opposed to the actual magnitude of them. Some of this information will be shown in tables and others in visual form, to convey as much detail as is possible. I used stepwise forward and stepwise backward regression extensively. Additionally, I used the p-values of a likelihood ratio test to compare ran null models (containing no independent variables) and compare it to a model with one additional variable added. If the p-value is 0.2 or less, I then take that variable forward. I then create a new ‘null’ model containing these variables and compare that to a regression model with one extra variable that did not produce a p-value of 0.2 in the previous round. Again, the likelihood ratio test p-value of 0.2 or less shows that these extra variables might be of importance, and they are added to the ‘null’ model in the next round of testing. I continue this method, until no more variables are significant. The model with the dependant variable and the various significant variables is run and I search for the regression coefficients that have a p of 0.05 or less and report on these. Additionally, I have tried to supplement the analysis with some forms of multivariate analysis, such as factor analysis, etc, so that underlying associations can be investigated.