Procedures, image acquisition, and processing
Depression
All patients underwent clinical assessments using the 17-item Hamilton Depression Rating Scale (HAM-D), Beck Depression Inventory (BDI), Young Mania Rating Scale (YMRS), and a visual analog scale (VAS) of mood (using a 100 mm linear scale, where 0 mm indicates the worst feeling and 100 mm represents the best feeling) in the morning at baseline (pre) and after a 4-week period of light exposure (post). An actigraphy system (Actiwatch 2; Respironics Inc., USA) was employed to measure environmental light, including both indoor and outdoor light, during the study period for both groups. Magnetic resonance imaging (MRI) data were collected using a 3 T MRI scanner (MAGNETOM Verio, Siemens or MAGNETOM Skyra Fit, Siemens), with a gradient strength of 45 mT/m and 32-channel array head coil. T1-weighted structural images were acquired using a 3-D magnetisation-prepared rapid gradient-echo sequence in the sagittal plane. Images were automatically processed with the longitudinal stream in FreeSurfer 7.1.1 to extract reliable volume estimate [