The present study was designed to evaluate the efficacy of intensive sleep retraining for treating insomnia and explore its potential mechanisms of action. Specifically, it sought to determine whether the resolution of conditioned insomnia is the main therapeutic ingredient of intensive sleep retraining, or whether the increase in homeostatic sleep drive due to sleep deprivation accounts for sleep improvements. To isolate those two components, this study compared the short and long-term efficacy of intensive sleep retraining and total sleep deprivation for the treatment of chronic insomnia in comparison to a control condition.

The pre-treatment period consisted of two consecutive weeks and was scheduled from Thursday to Thursday to coordinate the treatment period over the weekends. At the end of the pre-treatment period, participants were informed of their assignment to one of the three conditions. Participants were required to report to the sleep laboratory on Thursday at 7:00 p.m. for the night. Their time in bed was restricted to 6.5 hours (11:00 p.m. to 5:30 a.m.) to increase homeostatic sleep pressure before treatment. After waking up, participants were asked to leave the laboratory and could attend their normal daytime activities, but daytime naps were not allowed. All participants were asked to report to the laboratory at 7:00 p.m. on Friday.

Treatments

The 21-hour treatment period was scheduled from 11:00 p.m. on Friday to 8:00 p.m. on Saturday. Subjects in both the intensive sleep retraining and total sleep deprivation groups experienced at least 38.5 hours of sleep deprivation: Friday 5:30 a.m. through Saturday 8:00 p.m. Time was set aside to re-explain the protocol, answer questions, assess suicide risk again and calibrate the polysomnography montage. Participants were continuously monitored throughout the laboratory period to ensure that they were following the instructions specific to their condition. They were provided with breakfast, lunch, dinner, and snacks, but were not allowed to consume caffeine or alcohol, or to exercise. After the intensive sleep retraining and total sleep deprivation interventions, participants were not allowed to drive home for safety reasons and were instead picked up by a friend or family member or provided with a taxi voucher. There was no information about cognitive behavioral therapy for insomnia, sleep education, or sleep hygiene that was provided to any of the participants during the study.

Intensive Sleep Retraining : This treatment involved a series of 42 half-hour sleep onset opportunities repeated every 30 minutes starting at 11:00 p.m. At the beginning of each 30-minute period, participants were instructed to lie down in bed, close their eyes and relax. They were left alone in the bedroom, the lights were turned off, and the door was closed. The sleep period began when the lights were turned off. Once sleep onset was detected by the recording technician, participants were allowed to sleep for 2 to 4 consecutive minutes before being awakened. If participants did not fall asleep, the trial ended after 25 minutes, with a five-minute interval before the next sleep attempt. Participants were not given feedback about whether they fell asleep or not. Between trials, participants were instructed to get out of bed, leave the room, and either sit in a chair or stand in another room. They could talk with the experimenter or read but could not watch television or use a computer.

Total Sleep Deprivation : Participants were instructed to remain awake during the 21-hour treatment period. They could engage in quiet activities in the laboratory (e.g., reading, watching TV, using the computer) or talk with the experimenter. They could not sleep or stay in their bedrooms. A research assistant was always present to ensure that the participant did not sleep.

Control: Participants were allowed to sleep for up to 8 hours starting at 11:00 p.m. While awake, they could engage in quiet activities in the laboratory (e.g., reading, watching TV, using the computer) but were not allowed to sleep or stay in the bedroom during the day. They could attend a 1.5-hour information session about cognitive behavioral therapy for insomnia after completing the 1-month follow-up assessment.

Post-Treatment and Follow-up

Post-treatment period involved two consecutive weeks immediately after the treatment protocol. After the laboratory period, all participants were instructed to resume their normal sleep-wake schedule.

Follow-up consisted of one consecutive week of monitoring beginning 3, 7, and 11 weeks after the treatment period.

Inclusion Criteria:

• Age between 18 and 60 years old;
• Diagnosis of chronic insomnia based on The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition criteria;
• Sleep onset latency ≥ 30 minutes for ≥ 3 nights per week for 2 weeks as measured by a daily sleep diary;
• Sleep efficiency ≤ 85% for 2 weeks as measured by a sleep diary;
• Significant distress or impairment of daytime functioning (score of at least 2 on item 5 or 7 of the Insomnia Severity Index);
• Have access to a computer with an Internet connection to complete questionnaires.

Exclusion Criteria:

• Active or unstable progressive medical condition (e.g., cancer) or degenerative neurological disease (e.g., dementia);
• Current diagnosis of major depression, dysthymia or anxiety disorders;
• Lifetime diagnosis of any psychotic or bipolar disorder;
• Other sleep disorders, sleep apnea (apnea/hypopnea index greater than 15) restless legs, or periodic limb movements during sleep (movement index with arousal greater than 15 per hour);
• Alcohol or substance use disorder in the past 12 months;
• Use of any drug known to affect sleep (e.g., cocaine) in the past 2 weeks;
• Current or planned pregnancy during the study;
• Night shift work or irregular sleep pattern (e.g., usual bedtime after 2:00 a.m. or usual wake time after 10:00 a.m.);
• Current suicidal risk;
• Body mass index greater than 32;
• Use of sleep-inducing drugs (prescription or non-prescription);
• Use of tobacco products.