A small study of Toronto college students is shedding light on a contributing factor of insomnia that might be hard to admit -- an adult fear of the dark.

Nearly half of the students who reported having poor sleep also reported a fear of the dark. Researchers confirmed this objectively by measuring blink responses to sudden noise bursts in light and dark surroundings. Good sleepers became accustomed to the noise bursts but the poor sleepers grew more anticipatory when the lights were down.

"The poor sleepers were more easily startled in the dark compared with the good sleepers," said Taryn Moss, the study's lead author. "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."

The abstract "Are people with insomnia afraid of the dark? A pilot study" from Ryerson University Sleep & Depression Lab is being presented June 11 at SLEEP 2012, the 26th annual meeting of the Associated Professional Sleep Societies (APSS) in Boston.

Colleen Carney, PhD, the principal investigator, said insomnia treatments are highly effective but not everyone responds or completely recovers. New approaches may be warranted. For example, the most effective insomnia treatments encourage people to leave the dark bedroom and go into another, lit room; however, this would not be a way to treat a dark-related phobia.

"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."