Indoor Artificial Light at Night and the Relapse Risk of Schizophrenia

A randomized crossover trial of ALAN intervention was conducted in patients with chronic schizophrenia in Anhui Mental Health Center from August 15 to September 30, 2022. All participants met the diagnostic criteria for schizophrenia in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-V). The enrolled patients were in the symptom-stable phase and were regularly prescribed antipsychotics (no change in medication regimen). The diets of all the participants were uniformly supplied during study. Patients with infectious diseases, eye diseases, or gastrointestinal diseases, or who used antibiotics at the time of recruitment, were excluded. The wards of the participants were all located in the same inpatient building. All included wards had the same size, layout, lighting and orientation of doors and windows. In normal conditions, each ward retains a small LED lamp (the same layout in all wards) at night as a source of lighting.

The study was divided into two stages. In the first stage, 10 wards were randomly selected as the intervention group (opaque black tape covering part of the light source), and another 10 wards were selected as the control group (no intervention). After a two-week washout interval, the second stage was carried out, with the two groups interchanging interventions. At the end of each intervention, participants completed a structured questionnaire scale to assess the relapse risk of schizophrenia, and then their fecal samples were collected.