Obstructive sleep apnea is commonly reported in Veterans with post-traumatic stress disorder, which can potentiate symptoms of anxiety and depression, daytime symptoms and worsen nightmares. Continuous positive airway pressure is the most effective therapy but adherence to treatment is suboptimal. The overarching theme of the proposal is to compare usual care to Ramelteon, in a randomized, clinical trial, investigating the effectiveness of physiological versus pharmacological intervention on sleep quality of life, insomnia severity and CPAP adherence.