The global prevalence of primary psychodermatologic disorders: a systematic review

The management of primary psychodermatologic disorders (PPDs) (i.e. psychiatric disorders with dermatologic presentation) is challenging. The scarceness of reported prevalence hinders the development of coordinated interventions to improve healthcare delivery. This review aimed to explore the global prevalence of PPDs. The review was conducted according to the Preferred Reporting Items for Systematic Review and Meta-Analyses statement. Of the 4632 identified publications, 59 were included. Five PPDs were investigated from the included studies: delusional parasitosis (n = 9), skin picking disorder (n = 26), trichotillomania (n = 26), tanning dependence (n = 5) and repetitive nail biting (n = 6). Delusional parasitosis was rare in the general population (prevalence ranging from 0.0002% to 0.03%), with higher rates in psychiatric settings (outpatient = 0.5%; inpatient = 0.1%). Other pathologic or subclinical forms of PPDs had a minimum prevalence of 0.3% (median = 7.0%; mean = 17.0%). The distribution of the prevalence rates was highly skewed, with large differences based on the study setting (e.g. dermatologic settings, psychiatric settings, and general population). The most common condition was pathologic skin picking (prevalence, 1.2%-11.2%) in the general population. Its rates were higher in the psychiatric settings (obsessive-compulsive disorder, 38.5%; Tourette syndrome, 13.0%; body dysmorphic disorder, 26.8%-64.7%). The prevalence of trichotillomania in the general population ranged from 0.6% to 2.9%, while that of pathologic tanning and nail biting could not be ascertained as the studies were mainly in students (range; 12.0%-39.3% and 3.0%-10.1%, respectively). In conclusion, PPDs are common, especially in the dermatologic and psychiatric settings. Further population-based studies are needed to determine more accurate prevalence rates.