A fear of things that go bump in the night isn't just a problem for kids.
A small, new study published Monday found that it may be relatively common for adults to be afraid of the dark, and that the fear might play a role in serious sleep problems, like insomnia.
"I don't think everyone with insomnia has this fear or phobia. But to improve treatment, we really need to understand anything that explains or contributes to sleep disorders," said study author Colleen Carney, an associate professor of psychology at Ryerson Unversity in Toronto, Canada.
In preliminary research presented at the SLEEP 2012 conference, 93 undergraduates completed questionnaires to help determine whether they were "good sleepers" or "poor sleepers," and also answered questions about whether or not they were afraid of the dark.
Nearly half of the 42 participants whose answers qualified them as poor sleepers said they had some fear of the dark, versus only about a quarter of the 51 good sleepers.
The researchers also gave participants headphones that emitted short, unexpected bursts of white noise. They monitored blinking responses both when the lights were on and when they were off in order to help determine how startled the participants were -- commonly referred to as the "startle response."
Overall, the poor sleepers were significantly more startled in the dark, suggesting they experienced increased or anticipatory fear when the lights were off. That fear could contribute to what the researchers call "increased arousal" once the lights are turned off, making it difficult for people to sleep. Insomnia -- which surveys suggest affects up to 40 percent of adults within a given year -- is broadly defined as the inability to fall or stay asleep.
One of the most surprising findings of the new study, Carney said, is simply how many adults confessed to being afraid of the dark.
"We really thought that we would have to catch fear of the dark by doing the startle paradigm," she said. "We were shocked by how many people acknowledged they were afraid of the dark as adults."
While past research has looked into the role that darkness plays in facilitating or increasing the startle response, Carney and her colleagues say they are the first to look at the role that a fear of the dark could play in keeping poor sleepers up at night.
"There's a long history of studies looking at human fear of the dark that goes back to the '60s and '70s, that shows that in the dark, humans can have an increased response to anything that would startle them," said Michael Decker, an associate professor at Georgia State University and spokesman for the American Academy of Sleep Medicine. "This can happen during wakefulness, like driving through a dark tunnel."
One big question the study does not address is exactly what drove participants' fear of the dark, Decker said. If the fear stems from a particular event in childhood, any subsequent treatment might differ from treatment given to a person who is simply anxious or jumpy.
"Before we treat anybody, we have to understand what the cause is," Decker cautioned. "With insomnia, you have to understand what the triggers are."
Indeed, the new study points to the need for continued research, in part so clinicians can appropriately treat patients, whether it is for insomnia, a phobia or both. For example, one of the strategies often recommended for insomniacs is leaving the bedroom if they're feeling anxious and can't sleep. But for someone who has a fear of the dark, that might not be appropriate.
“That’s how you would reinforce the phobia. If you allow people to leave and to avoid, we’re telling them to go into a lit room and wait for the anxiety to go down, fueling the phobia," Carney said. "We might have to modify some of our effective treatments.”
HuffPost Lifestyle is a daily newsletter that will make you happier and healthier — one email at a time. Learn more