Morissette, 35, tells Runner's World that "running has made being depressed impossible. If I'm going through something emotional and just go outside for a run, you can rest assured I'll come back with clarity."
The Grammy-winning singer, who has run two marathons, tries to live a healthy lifestyle, including eating lots of kale. But she still occasionally indulges "in red wine, and it's fun to have medical marijuana once in a while," she says. "I still party and include a little debauchery."
Always an active athlete – Morissette says she was once a "hard core" swimmer who trained seven days a week – she sometimes struggles with the motivation to run. "But I tie my laces, put on a tight bra and get out there like a little robot. The first 10 minutes are excruciating, but soon I get into the flow."
Morissette ran the two marathons for charity and did November's New York City Marathon with Edward Norton on behalf of the Maasai Wilderness Conservation Trust. In October, she did the Bizz Johnson Trail Marathon through Lassen National Forest in California, representing the National Eating Disorders Association.
"I struggled with eating disorders, especially in my teens," she says, "but I've noticed when I treat my body like an instrument instead of an ornament, my relationship with food completely changes.'
To ease aching muscles, she takes ibuprofen. But after a long run she sits in an ice bath to "get that inflammation down. It's not too pleasant, but you get used to it."