Sequential approach to treating comorbid PTSD and depression This study is the first randomized control trial to rigorously test a sequential approach to treating comorbid PTSD and major depressive disorder. Findings from a trial of 52 patients undergoing three types of treatment regime - using only Cognitive Processing Therapy (CPT), using Behavioural Activation Therapy (BA) with some CPT, or CPT with some BA - found that a combined treatment protocol resulted in meaningful reductions in PTSD and depression severity, with improvements maintained at six-month follow-up investigations. "We sought to examine whether a protocol that specifically targeted both PTSD and comorbid depression would benefit those with this dual diagnosis compared with a solely PTSD-focused protocol," says Flinders PTSD research expert Professor Reg Nixon.