A new book argues sleeping pills aren’t the answer to chronic insomnia, reports The Atlantic.

According to the new book Why We Sleep, by Matthew Walker, the director of the Sleep and Neuroimaging Lab at the University of California, Berkeley, the sleep people get on sleeping pills like Ambien is not true sleep. Drugs like these simply “switch off the top of your cortex, the top of your brain,” he explained to New York Magazine, “and put you into a state of unconsciousness.” That’s not sleep; that’s cryogenics. According to Walker, sleeping-pill sleep doesn’t have the same restorative powers—and there are lots, from an immune boost to emotional resilience—as good, old-fashioned zzzzs.