Meditation and sleep apps have raised hundreds of millions of dollars in venture capital, hinting at the start of a new lifestyle business, reports NBC News.

Dr. Dianne M. Augelli, an assistant professor at the Weill Cornell Medicine Center for Sleep Medicine and physician at New York Presbyterian, cautioned that sleep and wellness can be complex issues that won’t be solved by an app.

“Expectations need to be tempered about what they can do,” Augelli said.

One obvious impediment to sleep the apps pose that both Augelli and Kennedy pointed out: screen time.