This article originally appeared in “Runner’s World / Zelle”

When does running go from being a “good thing” to too much of a good thing?

Jenny Shepherd, 39, had always run to deal with stress. But when postpartum depression struck after the birth of her third child in 2011, Shepherd ramped up her coping strategy. The more she ran, the more she depended on it—to the point where taking a day off left her feeling anxious and depressed.“I’d squeeze in the miles whenever I could. Even if I felt tired, I’d rather suffer through an uncomfortable workout than deal with the guilt of not doing it,” says Shepherd, of Oak Park, Illinois.

This past January, Shepherd committed to a 200-mile challenge through her running group, and ran herself into an ankle injury and a boot. When the boot came off, Shepherd’s doctor gave her clearance to run one mile. She ran four. “I couldn’t seem to stop myself,” she says.

There’s a fine line between being a dedicated athlete and being addicted to running, but experts have come to recognize exercise addiction as a legitimate problem—akin to alcoholism, binge eating, and other addictive disorders.

Shepherd’s story illustrates some of the telltale signs, one of which is running through injury, says Heather Hausenblas, Ph.D, a health psychologist at Jacksonville University in Jacksonville, Florida., who has studied exercise addiction for more than 20 years. “When you are injured, are you able to stop and take time off to heal? People who are addicted cannot—or if they do, they experience withdrawal symptoms such as anxiety, depression and trouble sleeping.”

“Another sign is that running becomes all-consuming,” says Hausenblas. “Someone who is addicted will give up all other activities in their life—family, friends, work—to get their runs in.”

“The Truth About Exercise Addiction” by Katherine Schreiber and Hausenblas (Rowman & Littlefield Publishers, February 2015) elaborates on the signs of exercise addiction and offers insight into the risk factors and treatment. The book includes the Exercise Dependence Scale, which Hausenblas helped develop. The scale looks at seven factors to determine if an individual is addicted to exercise:

Withdrawal effects:

  • Do you experience withdrawal symptoms when you stop?
  • Continuance: Do you continue to exercise despite recurring problems?
  • Tolerance: Do you feel a need to always do more to achieve the same effect?
  • Lack of control: Are you unable to control your exercise habits?
  • Reduction in other activities: Are you spending less time doing other things?
  • Time: Is exercise consuming all of your time?
  • Intention effect: Do you exercise more than you intend?

Based on scale responses, an estimated 25 percent of runners suffer from exercise addiction, compared to about 0.3 percent of the population in general, Hausenblas says.

Why is this number so much higher for runners? For one, it’s socially acceptable. “It’s okay to say, ‘I’ve got to do my 16-mile run today because I’m training for a marathon,’” says Hausenblas. “You get praise for doing it. It’s valued in our society.”

There is also something to be said about endorphins, which have been linked to improved mood. “People who are exercise-dependent need this, or their mood is strongly affected,” Hausenblas says. While various forms of exercise result in an endorphin boost, it tends to be greater with running and other forms of cardio.

For the nonexerciser—and even for someone who is exercise dependent–addiction to running might not seem like such a bad thing. But the consequences can be serious.

Physically, these include an increased risk of injury, exhaustion, and even cardiac damage, says Emilio Landolfi, Ph.D, a kinesiologist at the University of the Fraser Valley in Abbotsford, Canada, who has researched exercise addiction. While these are similar to the effects of overtraining, a person who is exercise dependent would likely continue to exercise when overtraining symptoms begin to appear. “Consequently, the damage is potentially much greater in the exercise addict versus the overtrained athlete,” Landolfi says.

If you believe you are addicted to running or exercise in general, Hausenblas advises keeping a diary of your workouts. Set reasonable goals to gradually decrease your mileage or time spent exercising, and talk to a close friend to hold you accountable. If you still can’t stop, seek professional help.

If you have a friend who shows signs of exercise dependence, carefully bring the issue to her attention, says Hausenblas. Make sure she is aware exercise addiction is a real condition. Don’t accuse her of being addicted, but instead use “I” statements to express how her behavior makes you feel.

For more advice on dealing with exercise addiction, check out “The Truth About Exercise Addiction.”