People with depression often have sleep apnea and doctors frequently confuse the two conditions, new research suggests.

Scientists from the University of Australia and Hospital of Perth have discovered that the development of sleep apnea and depression may be related and that treatment with continuous positive airways pressure (CPAP) is helpful to both conditions.

The findings, published in Journal of Clinical Sleep Medicine, are based on an analysis of nearly 300 sleep apnea patients, 73 percent of whom had clinically significant depressive symptoms. The researchers also found 96 percent of the apnea patients who adhered to CPAP therapy experienced a significant decline in their depression.

“Effective treatment of obstructive sleep apnea resulted in substantial improvement in depressive symptoms, including suicidal ideation … The findings highlight the potential for sleep apnea, a notoriously underdiagnosed condition, to be misdiagnosed as depression,” said David R. Hillman, M.D., clinical professor at the University of Western Australia and sleep physician at the Sir Charles Gairdner Hospital in Perth in a statement.

According to the American Academy of Sleep Medicine more than 25 million Americans have sleep apnea, a condition that causes sufferers’ breathing to stop briefly and repeatedly during sleep. Chronic snoring is the most common symptom.

Dr. Hillman concluded apnea is often misdiagnosed for depression because patients have similar symptoms in both affections.