Harmat 2008.

Study characteristics
Methods	Study type: RCT Design: 3‐arm, parallel group design Blinding: single blind; group allocation was coded for the person performing the statistics (Harmat 2014 [pers comm])
Participants	Sample: students with poor sleep documented by PSQI scores > 5 n: 94 randomised (64 included in this review). 94 completed and included in the analyses Age: mean 22.6 (SD 2.9, range 19–28) years Sex: 21 men, 73 women Setting: participants' homes Country: Hungary
Interventions	Intervention 1 (n = 35): music group. Participants listened to researcher‐selected classical music. Participants administered the music themselves. The listening device was not reported. Music characteristics: The Most Relaxing Classical (2 CD, Edited by Virgin 1999). Popular pieces from Baroque to Romantic Length of sessions: 45 minutes Frequency of sessions: daily at bedtime Duration of intervention period: 3 weeks Intervention 2 (n = 30): audiobook group (not included in review). Participants listened to researcher‐selected audio books. Control (n = 29): no intervention
Outcomes	Sleep quality (assessed with PSQI) mean (SD) at baseline and post‐intervention Depression (assessed with BDI)a aOutcome not included in this review since it was not measured in the control group.
Notes	Trial start and end dates: 2006 Funding sources: supported by the Hungarian Ministry of Education, the National Research Fund (Hungary), the Ferenc Faludi Academy, and the János Bolyai Research Fellowship of the Hungarian Academy of Sciences Protocol registration: none found
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Comment: used a computerised randomisation table and variable block randomisation.
Allocation concealment (selection bias)	Unclear risk	Comment: no information on allocation concealment.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Comment: due to the nature of the intervention, blinding of participants was not possible. It is likely that this affected the subjective outcome measures. The intervention was used at home with no personnel involved.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Comment: group allocation was coded (Harmat 2014 [pers comm]).
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: no attrition in the included groups (Harmat 2014 [pers comm]).
Selective reporting (reporting bias)	Low risk	Comment: we found no published protocol on this study. Outcomes from the no‐intervention control group were not reported in the publication, but were provided by the first author on request (Harmat 2014 [pers comm]). These data did not alter the results or conclusions of the trial.
Other bias	High risk	Comment: the trial design involved a difference between the intervention and control groups. The intervention group registered sleep quality once a week, whereas the control group only registered sleep quality before and after the intervention period. In addition, the intervention group, but not the control group, was contacted weekly by telephone to assess compliance with the protocol.