Randomization, masking, and intervention
The patients were randomly allocated to either the BL or DL group using the envelope method in a 1:1 ratio. The random allocation sequence was generated by HH and MS, and HH enrolled the patients. The participants then drew envelopes and were assigned to the BL or DL group. The outcome of the randomization was not concealed. The BL and DL groups were exposed to light therapy devices emitting 10,000 lx (Bright Light Me +; Solartone, Japan) and 50 lx (Wake-Up Light HF3520; Royal Philips, Netherlands), respectively. The daily light exposure protocol was administered for 30 min between 7:00 and 7:30 a.m. every morning for 4 weeks. At the inception of the study, participants were instructed to maintain their lifestyle unchanged throughout the study’s duration. Also, the patients were continued on the same medications and dosages throughout the study period.