June 12, 2012 (Boston, Massachusetts) — Some adults with insomnia may actually be afraid of the dark, a small pilot study of college students hints.

Researchers found that more students who were poor sleepers reported they are afraid of the dark, and then confirmed this finding using objective measures of anxiety in dark and light conditions.

A phobia related to darkness may bring on anxiety and a state of arousal when people turn out the lights at bedtime, in turn fueling sleep problems, the findings suggest.

"This could be an eye-opener, if we find this phobia in a range of adults with insomnia," principal investigator Colleen Carney, PhD, from Ryerson University Sleep & Depression Laboratory in Toronto, Ontario, Canada, told Medscape Medical News.

"It means we have to start assessing for a phobia in poor sleepers, which we don't do at the moment. The good thing is we can treat fear of the dark with systematic exposure therapy that could be done at a sleep clinic or any clinic."

Dr. Carney reported her findings here at SLEEP 2012: Associated Professional Sleep Societies 26th Annual Meeting.

Results Interesting, Relevant

"These results are very interesting and relevant," Geneviève Belleville, PhD, from Laval University, Quebec, Canada, who was not involved in the study, told Medscape Medical News.

"We have known for a long time that anxiety is closely related to insomnia. Insomniacs report more stress, worry more, and are more likely to suffer from anxiety disorders. However, to my humble knowledge, I think this is the first time that insomnia is directly put in relation with dark-related phobias," she added.

In treating people with insomnia, Dr. Carney said she's found they often have a lot of behaviors that suggest they have a phobia about the dark. For example, they may sleep with the light, computer, or TV on. "Another common scenario in insomnia is they fall asleep on the couch, they go upstairs, get into bed, turn off the light, and it's like a switch goes off and they are wide awake," she explained.

This prompted her to investigate fear of the dark in 93 college students (76% women; mean age, 22 years). All of them completed the Insomnia Severity Index, which classified them as good or poor sleepers, and a fear of the dark questionnaire.

"We didn't think people were actually going to admit that they were afraid of the dark," Dr. Carney told Medscape Medical News, "but surprisingly almost half of the patients admitted to being afraid of the dark." And more poor sleepers (46%) than good sleepers (26%) said they had current fear of the dark (P = .05).

Fear Confirmed Objectively

The study team also assessed fear of the dark objectively by assessing the startle (eye blink) response. "We are looking at blinking, because this is one of the most robust ways to look at startle, it's something we can't control, and we hypothesized that the poor sleepers would startle more in the dark but not in the light," Dr. Carney said.

To do this objective test, the researchers had participants listen to bursts of a sudden noise in headsets while in a bedroom in both light and dark conditions. "They would hear a tiny sound, not a disturbing sound, but enough that if you are tense it will make you startle," Dr. Carney explained.

The researchers found that, in the light, the good and the poor sleepers had exactly the same startle response, but in the dark, "some interesting things happened," Dr. Carney said.

"The poor sleepers were more easily startled. They blink right after the sound and interestingly they become more and more scared as the experiment goes on in the dark. But when we do the test in the light, this goes away; bring back the dark and they actually get more anxious as time goes on, which is something that shouldn't happen unless you have a phobia," she explained.

In contrast, Dr. Carney found that the good sleepers were less scared in the dark and actually became less scared in the dark as time went on, "which is what we would expect with habituation," she said. "Even if something startles you initially you start to get use to it. So the good sleepers actually habituate but the poor sleepers actually develop anticipatory anxiety and get more anxious as the test goes on."

Implications for Treatment

This study specifically looked at young adults, and Dr. Carney said her team would now like to test for fear of the dark in a wider range of adults who are poor sleepers.

The current findings, she said, could have "important" implications for the use of cognitive-behavioral therapy (CBT) for insomnia vs phobia.

"CBT is the gold standard for chronic insomnia and one of the things we get people to do, which is every effective, is stimulus control. We ask them to leave the bedroom whenever they are awake or upset or tense. The problem with that is that we send them to the next room, which is going to be lit and that is actually how phobia is maintained. This may be one of those cases were we have to modify CBT for insomnia."

Dr. Belleville agrees. "If we were to confirm that an individual cannot sleep because he or she is afraid of the dark, the proposed treatment strategies would be completely opposed to those we normally offer to insomniacs. For example, we might use repeated and prolonged exposure to dark places, including the bedroom, to help the person to overcome his or her fear," she explained.

The authors and Dr. Belleville have disclosed no relevant financial relationships.

SLEEP 2012: Associated Professional Sleep Societies 26th Annual Meeting. Abstract #0666. Presented June 11, 2012.

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