FKBP5 and major depressive disorder: As many studies have reported, FKBP5 variants have been linked to neuropsychiatric conditions, including depression, anxiety, posttraumatic stress disorder and cognitive impairment, all of which share some symptoms with sleep disturbance (Wang, Shelton & Dwivedi, 2018; Hernández-Díaz et al., 2019; Terrelonge et al., 2022).