Sleep apnea therapy may have effects beyond treating the sleep disorder that causes people to stop breathing during sleep (thereby leading to disturbed sleep) — new research suggests it could also help to ease depression.

Cleveland Clinic researchers presented a study at the annual SLEEP2012 conference showing that use of positive airway pressure (PAP) for obstructive sleep apnea is also linked with improved scores on a test for symptoms of depression, called the PHQ-9.

“The score improvements remained significant even after taking into account whether a patient had a prior diagnosis of depression or was taking an anti-depressant,” study researcher Dr. Charles Bae, M.D., said in a statement. “The improvements were greatest in sleepy, adherent patients but even non-adherent patients had better PHQ-9 scores.”

Bae added that married people seemed to benefit the most from the PAP treatment in terms of depressive symptoms, with their scores on the PHQ-9 improving more than people who used PAP who are single or divorced.

Plus, people who used the PAP for more than four hours per night experienced greater gains in easing depression than people who used it fewer times.

The study included 779 people with obstructive sleep apnea who filled out the PHQ-9 form before and after sleep apnea treatment.

Sleep disorders, like sleep apnea, and depression are known to be linked, according to the National Sleep Foundation, though it’s not completely clear whether the depression brings on the sleep problems, or if sleep problems make people depressed.

A 2003 study in the Journal of Clinical Psychiatry showed that people with depression have five-fold increased risk of sleep-disordered breathing, such as sleep apnea.

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