Fear of Dark May Morph into Insomnia

Fear may contribute to increased arousal once the lights are turned off at bedtime, study shows.

People with insomnia may not sleep well because they have an underlying fear of the dark, researchers suggested here at the annual meeting of the Associated Professional Sleep Societies.

About 46 percent of subjects with insomnia reported they had a fear of the dark compared with 26 percent of good sleepers, said Taryn Moss Atlin, MS, a PhD student at Ryerson University, Toronto.

Poor sleepers also experienced a decrease in eyeblink latency when confronted with white noise stimuli — that is, their startle index increased compared with their first encounter with the noise, while good sleepers had decreased eyeblink latency — meaning they were able to accommodate the noises, said Atlin.

In her study, Atlin recruited 93 individuals from the university setting. The average age of the participants was 22 years. About 73 percent were women.

Participants completed self-report questionnaires which measured the Insomnia Severity Index, as well as a questionnaire developed at Ryerson to assess fear of the dark. They then performed the startle test, listening to white noise through headphones in a lighted room and in a darkened room.

Among the poor sleepers, the eyeblink latency was 55 milliseconds based on readings from an electrooculogram when they first encountered the sudden noise in the first phase of the testing. The next time they listened through headphones in a darkened environment, their eyeblink latency decreased to about 42 ms. Atlin said that indicated that instead of adapting to the noise, they became more startled by it the second time around.

In good sleepers, the first encounter with the noise during the dark stage resulted in eyeblink latency of 40 ms; but in the second phase, the eyeblink latency increased to 60 ms, indicating they were getting accustomed to the noise and it didn’t startle them as much.

“The poor sleepers were more easily startled in the dark compared with the good sleepers,” said Atlin. “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.”

“Fear of the dark may contribute to increased arousal once the lights are turned off at bedtime for this subset of poor sleepers,” Atlin continued. She suggested that rather than treating patients with insomnia with medications, clinicians should first attempt to determine if there is something that can be achieved through cognitive behavior therapy.

“I have patients who are similar to these,” said Jeanne Melvin, MS, a sleep behavior specialist in Santa Monica, Calif., who scrutinized Atlin’s poster at the meeting. Melvin, who did not participate in the study, told MedPage Today that when she encounters patients who complain of insomnia and admit they leave a light on for fear of the dark, she uses nonmedicinal therapy.

She said that in one case she simply asked her insomniac/fearful patient to replace the regular light with a red light bulb. “It worked like a charm,” Melvin said. “She went right to sleep.”

By Ed Susman