Sheryl Crow has learned to control her bouts of depression but the condition still keeps her awake at night.
The All I Wanna Do rocker has battled chronic depression for years, but has learned to accept that it's part of who she is.
She explains, "I spent a lot of the last three years just being completely debilitated. Part of it was because of where I was in my life, hitting 40.
"My dad and I both have severe mood swings. We laugh about it, but we have really high highs and really low lows.
"I wake up feeling like right outside my door was this gnawing thing."
Her mood swings don't make getting a good night's rest easy - Crow suffers from a "sleep paralysis" that she describes as a fear of falling asleep.
She adds, "It's a shadow for me. It's part of who I am. It's constantly there. I just know how, at this point, to sort of manage it."