Evidence map›Paper›PMID 25515108›Full record

SynthesisSleep2015

Effect of Placebo Conditions on Polysomnographic Parameters in Primary Insomnia: A Meta-Analysis.

Alexander Winkler, Winfried Rief

Open access · bronzeAbstract readMeta-Analysis
PubMed Full text at PMC Publisher
In one paragraph

Synthesis in Sleep, 2015. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 32 papers, 2 of them syntheses that pooled it.

0numbers the graph read from it
0cells of the map it votes in
32citing papers in PubMed, 2 pooled it
2.8field-weighted citation impact, top 10% of its field
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.

3 · Its place in the literature

Who cites it

32 citing papers in PubMed, 2 syntheses or guidelines pooled it, 78 citations in OpenAlex.

  1. Pooled it
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  4. Efficacy and Safety ofNutrients · 2026
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  6. A randomized pilot study of a wearable device using variable complex weak magnetic fields among participants with insomnia symptoms.Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine · 2025
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4 · The record

Corrections and comments

PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

2 authors at 1 institution in 1 country.

Alexander WinklerUniversity of Marburg, Department for Clinical Psychology and Psychotherapy, Marburg, Germany.
Winfried RiefUniversity of Marburg, Department for Clinical Psychology and Psychotherapy, Marburg, Germany.
Philipps University of Marburg · DE

Funding

No grant is acknowledged in the PubMed record.

6 · The paper itself

Abstract

STUDY

objectivesLittle is known about the role of placebo response in the pharmacotherapy of primary insomnia, especially about the effect of placebo intake on objectively assessed outcome variables. Our aim was therefore to conduct an effect-size analysis of placebo conditions in randomized controlled drug trials addressing primary insomnia also including polysomnography.

designWe conducted a comprehensive literature search using PubMed, PsycINFO, PSYNDEX, PQDT OPEN, OpenGREY, ISI Web of Knowledge, Cochrane Clinical Trials, and the World Health Organization International Clinical Trials Registry Platform. The meta-analysis used a random effects model and was based on 32 studies reporting 82 treatment conditions covering a total of 3,969 participants. Special emphasis was given to the comparison of objective and subjective outcomes and the proportion of the placebo response to the drug response. MEASUREMENTS AND

resultsEffect sizes estimates (Hedges g) suggest that there is a small to moderate yet significant and robust placebo response reducing the symptoms of insomnia in terms of sleep onset latency (-0.35), total sleep time (0.42), wake after sleep onset (-0.29), sleep efficiency (0.31), subjective sleep onset latency (-0.29), subjective total sleep time (0.43), subjective wake after sleep onset (-0.32), subjective sleep efficiency (0.25) and sleep quality (0.31). Thus, the placebo response was also evident in objective, physiological (polysomnographic) variables. Our results indicate that 63.56% of the drug responses are achieved even in the placebo groups.

conclusionsIn light of these strong placebo responses, future studies should investigate how to exploit placebo mechanisms in clinical practice.

Indexed as

Placebo EffectPolysomnographyAdultAgedFemaleHumansMaleMiddle AgedRandomized Controlled Trials as TopicSleepSleep Initiation and Maintenance DisordersTreatment OutcomeWakefulnessinsomniameta-analysisplacebopolysomnographicreviewtreatment

Identifiers

PMID25515108
PMCPMC4434559
OpenAlexW92598670

What OpenQuestion holds

Textmetadata
Read underepoch 390

Registered trials

None linked

Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.