Delusional disorder (DD) is characterised by delusions, sometimes bizarre, which are idiosyncratic beliefs that are resolutely upheld despite being contradicted by what is generally accepted as realistic or rational American Psychiatric Association (APA), 2013; Hooley, Butcher, Nock, & Mineka, 2017; Ibanez-Casas & Cervilla, 2012). Subtypes include erotomanic, grandiose, jealous, persecutory, somatic, mixed, and unspecified. Hallucinations, manic, and major depressive episodes may be part of DD, however, they are not as prominent as the delusion(s) and are related to the delusion’s overall theme (APA, 2013). Some individuals with DD may go on to develop schizophrenia. Brief psychotic disorder (BPD) must contain one or more features such as delusions, hallucinations, and disorganized speech, as well as potentially grossly disorganized or catatonic behavior (APA, 2013; Hooley et al., 2017). This may also occur postpartum. Individuals who are diagnosed with BPD often have a pre-existing personality disorder or psychoticism-related traits. While DD may have a gradual onset which expands or is additive over time, BPD has a sudden onset (APA, 2013). In order to diagnose DD, the delusional state must last for more than a month, and in fact, can occur over the course of a lifetime after onset. On the other hand, BPD must have symptoms for at least a day, but duration must be less than a month, followed by a complete return to functioning (APA, 2013; Hooley et al., 2017). DD has no clear trigger while BPD is often triggered by an overload of stress (Hooley et al., 2017; Pruessner, Iyer, Faridi, Joober, & Malla, 2011). Delusions can be seen in a wide variety of mental and neurological illnesses (Ibanez-Casas & Cervilla, 2012), as with psychoses, however, it is the brevity of BPD that makes it distinct.

A major difference between the two illnesses is seen in terms of functioning. Apart from delusions, an individual with DD is not generally greatly impaired in functioning or noticeably odd, however, during an episode of BPD, there is often massive impairment with emotional turmoil and confusion with rapid affect shifts (APA, 2013; Hooley et al., 2017). Individuals with DD may have social, marital, and work related issues associated with their delusions, have irritable or dysphoric mood, litigious or antagonistic behavior, and certain subtypes are associated with legal difficulties, and anger, however, functioning may not be severely affected. BPD in opposition can create such intense failures to function, that protective supervisory attention may be required to monitor basic care while someone is having an episode, as well, the risk of suicide increases during that time (APA, 2013). With DD, general behavioral deterioration is rarely seen, even when chronic (Hooley et al., 2017), and with BPD there is a high rate of relapse, but social functioning and symptomology outcomes are excellent (APA, 2017). Individuals with both disorders are not as likely, as with some others, to seek treatment. This is due to the fact that impairment of function may be minimal with DD (Ibanez-Casas & Cervilla, 2012), and that the duration of BPD can be very brief (Hooley et al., 2017).

Except with the jealous type which is more male orientated, individuals with DD are equally likely to be male or female, while individuals with BPD are twice as likely to be female. The mean age of onset of DD is older, generally around the age of 40, however, can occur in very young people and also exhibit in the elderly, while BPD is often diagnosed around the age of 30, and can be seen in people as young as adolescents (APA, 2013; Ibanez-Casas & Cervilla, 2012). There are common genetic threads with both disorders in that close relatives of people with DD have increased rates of DD themselves and/or paranoid personality traits (Ibanez-Casas & Cervilla, 2012), and likewise, close relatives of persons with BPD have increased rates of psychotic disorders (Pruessner, Iyer, Faridi, Joober, & Malla, 2011).

References

American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Washington, DC: Author.

Hooley, J. M.,Butcher, J. N., Nock, M. K. & Mineka, S. (2017). Abnormal psychology(17th ed.). Boston, MA: Pearson Publishing.

Ibanez-Casas, I., & Cervilla, J. A. (2012). Neuropsychological research in delusional disorder: a comprehensive review. Psychopathology, 45(2), 78-95. doi:10.1159/000327899

Pruessner, M., Iyer, S. N., Faridi, K., Joober, R., & Malla, A. K. (2011). Stress and protective factors in individuals at ultra-high risk for psychosis, first episode psychosis and healthy controls. Schizophrenia research, 129(1), 29-35. doi: 10.1016/j.schres.2011.03.022