I thought this was interesting, but I suspected this for some time.
http://www.lifescript.com/articles/3522.asp?Bid=22170&Sid=3621250&Eid=35649326-875F-463D-BDEF-D52BC2823D7B
The sleep-breathing disorder sleep apnea had been previously linked to a higher risk of symptoms of chronic fatigue, but a new study finds that sleep apnea may also increase a patient's risk of depression. According to research conducted at the University Community Hospital Sleep Center in Tampa, Florida, patients diagnosed with sleep apnea are up to 40% more likely to be taking prescript
ion antidepressants. Furthermore, many apnea patients' depression may continue to go undiagnosed, its symptoms masked by those of the breathing disorder. Researchers suggest further studies to determine whether the most effective known sleep apnea treatment, continuous positive airway pressure (CPAP), may also alleviate depression symptoms.