Lead author Taryn Moss and principal investigator Colleen Carney of Ryerson University in Toronto measured blink responses to sudden noise bursts in light and dark surroundings.
Good sleepers became accustomed to the noise bursts but poor sleepers grew more anticipatory when the lights were down, the researchers found.
"The poor sleepers were more easily startled in the dark compared with the good sleepers," Moss said in a statement. "As treatment providers, we assume that poor sleepers become tense when the lights go out because they associate the bed with being unable to sleep. Now we're wondering how many people actually have an active and untreated phobia."
Carney said insomnia treatments are highly effective but not everyone responds or completely recovers.
"We may need to add treatment components for these patients and adapt existing treatment components in light of the phobia," Carney said. "A lot more research is needed, but we believe we have stumbled across an unmet treatment need for some poor sleepers."
The findings were presented at Sleep, the 26th annual meeting of the Associated Professional Sleep Societies in Boston.