Search

Psychiatric symptoms are frequent in neurocognitive disorders and dementias. Psychotic symptoms, mainly hallucinations and delusions, may appear in up to 50% of cases, influencing morbidity and mortality. Genetic, neurobiological, and environmental factors are involved in their onset. We conducted a narrative review of primary articles developed in humans that analyzed the genetic and neurobiological basis of psychosis in dementias. Evidence suggests that there are genetic risk variants for presenting psychosis in dementia. How genetic variants are related to schizophrenia, dementia, and other neurodegenerative disorders is under discussion. Candidate gene studies have found and genetic variants are associated with psychosis in dementia while genome-wide association studies have shown variants located in y . Epigenetic studies are scarce but have detected differences in the methylome of people with dementia and psychosis. On the other hand, alterations of the cholinergic, serotonergic, dopaminergic, and gabaergic neurotransmitter systems and the excitatory-inhibitory balance have been described in dementia. From a functional and anatomical point of view, there are alterations in several regions, mainly in the frontal area and other sensory processing and integration areas. Finally, we describe the influence of cognitive alterations in the genesis and maintenance of delusions and discuss the phenomenological overlap with confabulations. Multiple genetic, neurobiological, structural, and cognitive factors influence the occurrence of delusions and hallucinations in persons with dementia. Further research is needed to understand the pathophysiology of psychosis in dementias. This approach would support the understanding of psychosis as a transdiagnostic entity., Competing Interests: The authors completed the ICMJE conflict of interest statement and declared that they received no funds for the completion of this article; they have no financial relationships with organizations that may have an interest in the published article in the last three years; and they have no other relationships or activities that may influence the publication of the article. Forms can be requested by contacting the responsible author or the Editorial Committee of the Journal., (This work is licensed under a Creative Commons Attribution 4.0 International License.)

Background: Multiple complex developmental disorder (MCDD) manifests as early-onset impairment across different domains. Although it could appear as a transitional condition between autism and childhood-onset schizophrenia, interest in MCDD has progressively waned. This study attempts to discern MCDD current relevance to avoid "throwing the baby out with the bathwater" too fast., Methods: All available studies published up to January 2024 were retrieved and evaluated following on the PRISMA guidelines for systematic reviews using the term "multiple complex developmental disorder" or "MCDD", without any filter for study design nor year of publication., Results: Only 16 studies were included and analyzed. Overall, a variable heterogeneity was observed in terms of country of investigation, study design, and clinical groups. Most of the included studies explored the construct of MCDD in developmental age, comparing MCDD mostly with autistic patients, and observing how the former group had higher levels of paranoia, illusions, and psychotic thoughts, whereas the latter showed more frequently difficulties in social interactions and stereotypical behaviors., Conclusion: Overall, these results showed how progressive changes in diagnostic criteria over time led MCDD to be abandoned as nosographic construct, leaving perhaps a diagnostic void between autism and psychotic disorders that needs to be further studied. A systematic review on the Multiple Complex Developmental Disorder (MCDD): a forgotten diagnosis between autism and schizophrenia., Competing Interests: Declaration of conflicting interestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.