Objective: Environmental conditions during early life may affect individual vulnerability to both physiological changes as well as psychiatric conditions, especially in those with a genetic susceptibility. Among all factors, sunlight exposure intensity has a crucial effect on affecting circadian functions high-risk individuals. A potential explanation of this relation is that excessive sunlight exposure is able to impair biological mechanisms, possibly through the dysregulation of serotonin and/or melatonin production/metabolism. The aim of this study was to evaluate the influence of excessive sunlight exposure in a sample of emergency psychiatry inpatients.
Methods: All subjects were consecutively recruited from the Psychiatric Inpatient Unit of San Luigi Gonzaga Hospital, Orbassano (University of Turin, Italy) from September 2013 to August 2015. Socio-demographic and clinical characteristics were carefully collected.
Results: We initially screened a sample of 900 patients; however, only 730 subjects voluntary accepted to participate in the study. Patients with admissions in spring/summer (a period in which daylight/darkness ratio is longer) showed a higher prevalence of involuntary admission, an earlier age at illness onset, a longer duration of hospitalization and admission for (hypo)manic episode.
Conclusions: Excessive sunlight exposure may exert a fundamental role on psychopathological conditions presumably affecting biological vulnerability. A better understanding of its effect on the course of bipolar and other psychiatric disorders may assist in tailoring the adequate treatment for patients resulting in a shorter stay within hospitalized settings and a better treatment response.
Keywords: Photoperiod; bipolar disorder; psychiatric admission; seasonality; sunlight.