Psoriasis, Schizophrenia and Disorders with Psychotic Features: Are They Linked?

Psoriasis is a chronic inflammatory skin disease with a high impact on quality of life. It is a psychophysiological skin disorder with several psychiatric comorbidities. Schizophrenia is the most debilitating neuropsychiatric condition and recent studies have suggested that inflammatory pathways are part of its etiopathogeny. A possible connection between psoriasis and schizophrenia, or other disorders with psychotic features, has been suggested, although the studies in this field are scarce. We decided to perform a systematic review based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), using the 5S model of evidence based on information services described by Haynes. Our aim was to analyse what has been published on this topic. Psoriasis, schizophrenia and disorders with psychotic features seem to share genetic, immune and inflammatory processes which would explain why they could be linked. Cytokine activity may modulate the Hypothalamo-Pituitary- Adrenal (HPA) and Sympathetic Adrenomedullary (SAM) axes in both cases. Anti-psychotic medication and some treatments used for psoriasis modify the complex network of cytokines involved in both psoriasis and schizophrenia/ disorders with psychotic features. This could explain, for instance, the reported adverse effects of some of the drugs used to treat psoriasis and schizophrenia. Further studies are necessary to explore the etiopathogenic correlations which may be found in psoriasis and schizophrenia with potential therapeutic relevance. More studies are necessary to confirm the evidence of a higher prevalence of psoriasis in schizophrenic patients and of psychotic features in psoriasis patients as well as the mechanisms that may be responsible.