Delusional Disorder Causes & Risk Factors

Unfortunately, due to the available technology and research methods, the exact causes of most psychotic disorders including delusional disorder are not known. However, scientists are interested to identify and understand the role of genetic, biologic, and psychological factors.

Genetic factors
It is not clear whether there is a familial pattern between delusional disorder and schizophrenia. Some studies suggest that delusional disorder is more common among individuals with relatives diagnosed with schizophrenia, while other studies suggest that there is no familial relationship between delusional disorder and schizophrenia. There is also limited evidence that avoidant and paranoid personality disorders are common among first-degree biological relatives of individuals suffering from delusional disorder.

However, the incidence of psychiatric conditions in individuals genetically related to those that suffer from delusional disorder suggests that there might be a genetic component to the disorder.

Biological factors
In order to better understand the disorder, scientists are trying to identify the biological support of delusions. Some of the studies conducted on this matter focused on comparing the brain activity of those that exhibit delusions and non-delusional individuals. Based on the brain activity's differences displayed by participants of both groups, individuals with delusions "...tend to react as if threatening conditions are consistently present," compared to the non-delusional participants where similar brain activity patterns are displayed only in certain conditions "...where the interpretation of being threatened is more accurate."(4)

Other studies suggest that there might be some abnormalities in some areas of the brain (such as basal ganglia and temporal lobe) that can play a certain role in the development of the delusional disorder. The basal ganglia and temporal lobe seem to play a significant role in three neurological disorders associated with delusions (primarily dementia, head injury, and seizures).

According to a study conducted in 2002, there might be a connection between delusional disorder and an increased level of plasma homovanillic acid (HVA) - a dopamine metabolite (the level of HVA is correlated to with severity of psychotic symptoms). Also, an increased prevalence of a polymorphism at the D2 receptor gene at amino acid 311 (cysteine-for-serine substitution) have been detected in individuals with delusional disorder with persecutory delusions.

Psychological factors
Cognitive and experimental psychologists suggest that individuals with delusional disorder may process the information erroneously due to the fact that they "...selectively attend to available information, make conclusions on the basis on insufficient information, attribute negative events to external personal causes, and have difficulty in envisaging other's intentions and motivations." (2) Studies conducted on how individuals with delusional disorder develop theories about reality suggest that they "tend to reach an inference based on less information than most people use" which leads to "delusional interpretations of ordinary events" where alternative explanations are not taken into consideration. Additional studies suggest that people prone to delusions "read" the people around them differently than the non-delusional individuals, but whether their perception of others is more accurate or poor is still subject of controversy. Also, individuals with delusional disorder develop an erroneous interpretation regarding how others perceive them.

Supporters of psychodynamic theories consider that paranoia is "a protective response" to the stress of coping with everyday life and maintaining a high self-esteem. In order to protect and maintain a positive self image, the person might view others as the cause of their personal struggles and difficulties, which become an "ingrained pattern of thought." (4)

Conditions & Diseases: Psychological & Mental Health

Delusional Disorder