The condition is on the rise because the most frequent cause is obesity, which continues its unrelenting climb among American adults, reports The New York Times.

Although the woman in her 50s had been effectively treated for depression, she remained plagued by symptoms that often accompany it: fatigue, sleepiness and lethargy, even though she thought she was getting enough sleep.

With depression no longer causing her persistent symptoms, her psychiatrist advised her to consult a sleep specialist.

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