There have been a number of medical studies that have sought to prove the causal links between sleep apnea and depressive disorders and whether the former was a contributing factor to the latter. And in each and every study, the link between sleep apnea and depression was categorically proven and established.
Sleep apnea can and does starve the brain of oxygen while the individual suffering from the disorder is sleeping. As the flow of oxygen into the bloodstream isn’t constant and stops and starts in an individual suffering from sleep apnea, it can effectively lead to oxygen depletion, which can cause damage to the frontal lobe of the brain, which is a direct contributory factor that can lead to, and cause of a number of depressive disorders
As it can also lead to inflammation and swelling in muscles and joints, sleep apnea is also regarded as a secondary cause of depression as it can prevent neurotransmitter activity, which can heighten and exaggerate symptoms of depression that have already started to manifest themselves. While it isn’t a primary contributory factor, because of the effect that sleep apnea has on neurological structure and activity of the brain, it is seen as being a secondary cause of, and contributing to the development of, a variety of depressive disorders.