Study designs of evaluations included in the review
Randomised controlled trials (RCTs) that included placebo groups and double-blinded assessment of the outcomes. Crossover designs were included but data were extracted only for the first treatment period.
Specific interventions included in the review
Flurazepam, estazolam, zolpidem, triazolam, quazepam, temazepam and lorazepam. These were all compared with placebo. The median duration of treatment was 7 days (range: 4 to 35).
Participants included in the review
People with chronic primary insomnia, in whom psychiatric and medical conditions had been ruled out as causes of insomnia. The particpants' age ranged from 18 to 65 years old (predominately middle-aged) and 60% were women.
Outcomes assessed in the review
Sleep-onset latency, total sleep time, the number of awakenings, and sleep quality were assessed.
How were decisions on the relevance of primary studies made?
The studies were selected after two separate reviews were conducted to code each study's eligibility.