The research follows the discovery by Siegel that the absence of orexin A appears to cause narcolepsy. That finding pointed to a major role for the peptide's absence in causing sleepiness. It stood to reason that if the deficit of orexin A makes people sleepy, adding it back into the brain would reduce the effects, said Siegel.

"What we've been doing so far is increasing arousal without dealing with the underlying problem," he said. "If the underlying deficit is a loss of orexin, and it clearly is, then the best treatment would be orexin."