A pragmatic , parallel-group randomized controlled trial of 164 adults ( 120 F : ( mean 49 years ( 18-78 years ) ) meeting Diagnostic and Statistical Manual of Mental Disorders , 5th Edition ( DSM-5 ) criteria for insomnia disorder , assigned to CBT ( n = 55 ; 40 F ) , imagery relief therapy ( IRT placebo ; n = 55 ; 42 F ) , or treatment as usual ( TAU ; n = 54 ; 38 F ) , was conducted .