Paranoia querulans is a type of persistent delusional disorder of the persecutory subtype, recognized under ICD-10 and DSM-IV. Being a classically described entity, evidence is lacking from its conceptualization as a nosological entity to diagnosis and treatment. Furthermore, controversy still exists regarding its interplay between the judicial and mental health systems.

To summarize current evidence and knowledge regarding Paranoia querulans on its conceptualization, ethiopathological explanations, therapeutical management and interface between psychiatry and the law.

A systematic review was undertaken between June and October 2020 in the PubMed, Web of Science and Scopus databases according to PRISMA directive. Key-terms: ((querul* OR vexatious) AND (paranoia OR delusio* OR neuros* OR behavi* OR complai*) OR litig*) AND psychiatry. No language or time restrictions were established.

A total of 1648 studies were initially identified (PubMed: 679; WOS: 945; Scopus: 24; other: 0); after duplicates were removed, n=1381 studies remained. After screening title and abstract, 56 studies were included. Their main content was categorized into: 1. Conceptualization (n=26): Neurosis (n=5), psychosis (n=9), behavioral disorder (n=5); no psychiatric diagnosis (n=7). 2. Descriptive psychopathology (n=8) 3. Etiopathogenesis (n=9): Social or personality basis (n=3), culture (n=4), trauma (n=1), cognitive decline (n=1) 4. Management (n=1) 5. Psychiatry and Law: same object, different objectives (n=12)

There is controversy regarding the nosological entity of querulousness, from psychosis to neurosis or behavioral disorders. Some authors consider this behavior to not be a psychiatric diagnosis. Furthermore, most papers dealt with a social or nurture-based origin. There is a dearth of information regarding treatment.

JPE has received CME-related fees from Lundbeck.