An app recently cleared by the FDA to combat PTSD-related nightmares shows promise, but is unlikely to replace medications and other therapies, experts say.

NightWare is an Apple Watch app that helps treat nightmares stemming from conditions like PTSD. It works by monitoring smartwatch movements and heart rate data to detect and interrupt bad dreams without waking the user with a vibration. The app is supposed to be used only with a prescription, and that’s a good thing, observers say.

“The downside to this approach is that it doesn’t do anything to the adrenaline response, so I would be concerned that the adrenaline is disrupting sleep even after the app wakes the user,” Dr. Aaron Weiner, a clinical psychologist who specializes in trauma, said in an email interview.

“It may also reduce the likelihood that someone will decide to seek therapy, which may ultimately be the most effective way to permanently address PTSD symptoms.”