Walsh 1998.

Methods	Double‐blind, placebo‐controlled, parallel group study
Participants	Insomnia diagnosis criteria (method of diagnosis): DSM‐IIIR criteria: minimum 1‐month history of disturbed sleep, characterised by a self‐reported sleep latency of ≥ 30 min and a self‐reported sleep duration of (mean ± SD) 4 ± 6 hr ≥ 3 nights per week. Additionally, complaints of significant daytime fatigue or decreased daytime functioning as a result of poor sleep must have been reported. Other diagnoses: any significant medical or psychiatric disorder as determined by clinical interview was excluded Number of participants randomised: n = 306 Trazodone: n = 100 Zolpidem: n = 102 Placebo: n = 104 Number of participants: n = 278 Trazodone: n = 90 Zolpidem: n = 91 Placebo: n = 97 Age: no specific data except that participants were aged 21‐65 years and that there were no age differences between groups Gender (M/F): 113 (37%)/193 (63%) Race/ethnicity: 253 (84%) white, 53 (16%) unspecified Country: USA Setting: 10 different US sites Included: aged 21‐65 years, meeting the DSM‐IIIR criteria and reporting during a 1‐week, single‐blind, placebo lead‐in period both of the following criteria on ≥ 3 nights: self‐report sleep latency of ≥ 30 min, and self‐report sleep duration of (mean ±) 4 ± 6 hr. Excluded: any significant medical or psychiatric disorder (as determined by clinical interview by a physician), history suggestive of sleep apnoea or PLM, smoking > 10 cigarettes per day, weight varying > 25% from desirable weight based on the Metropolitan Life Insurance Table, pregnancy or risk of becoming pregnant, and lactation. Recent history of drug addiction, alcoholism or drug abuse; history of sensitivity to CNS depressants, regular use of any medication that would interfere with the study, use of any investigational drug within 30 days of study entry and previous use of zolpidem precluded participation. Benzodiazepines or non‐prescription sleep medication had to be discontinued for (mean 177 SD) 7 ± 25 days, depending upon duration of action. Finally, a positive urine drug screen for CNS‐active drugs, participation in a weight loss programme, shift work or any other regularly changing sleep schedule, precluded study participation. Withdrawals: n = 28 Trazodone: n = 10 (adverse events n = 5) Zolpidem: n = 11 (adverse events n = 5) Placebo: n = 7 (adverse events n = 2) Baseline imbalances: none obvious, but demographic data were not well described.
Interventions	Intervention: trazodone 50 mg taken nightly at bedtime. Comparator 1: zolpidem 10 mg taken nightly at bedtime Comparator 2: placebo taken nightly at bedtime
Outcomes	Primary outcomes Subjective sleep latency and subject sleep duration Secondary hypnotic efficacy measures: ease of falling asleep, NAW, subjective wake time after sleep onset and sleep quality Participant global impression of effect of therapy: number and % of participants responding, sleep status, sleep improvement, time to fall asleep and sleep time Secondary outcomes Impact on ability to function Adverse events
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No mention was made regarding the method of randomisation.
Allocation concealment (selection bias)	Unclear risk	No details given
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	No details given regarding how different capsules for zolpidem and trazodone influenced blinding
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No details given
Incomplete outcome data (attrition bias) All outcomes	High risk	Although only 28/306 participants dropped out (Pg 192, last paragraph of "Patients") the analysis was not ITT and the number of participants reported in the outcome data changed from the original reported sample size without adequate justification.
Selective reporting (reporting bias)	Unclear risk	No details given
Other bias	High risk	Funded by a pharmaceutical company with no evidence of independence of results reported