Lucid Dreaming and the Feeling of Being Refreshed in the Morning: A Diary Study

Round 1

Reviewer 1 Report

Lucid Dreaming and the Feeling of Being Refreshed in the Morning: A Diary Study

Schredl, Dyck & Kühnel

In this study Schredl and colleagues investigated the association of sleep quality and lucid dreaming. 149 participants engaged in an lucid dreaming induction course and kept a dream diary for 5 weeks. The authors show that there was no negative effect of lucid dreaming on subjective sleep quality (i.e. feeling of being refreshed in the morning). Even more, lucid dreaming was associated with eleveated levels of subjective feelings of refresh in the morning.

Overall, the present study is potential interest. There are only some points in need of clarification.

Major comments:

Comment 1: While I find the present study interesting, it would be worthwhile if the authors would make a stronger argument for the relevance of their work. Please make clearer (both in the introduction as well as discussion) why the research question and associated results are of potential relevance/interest to the reader.

Comment 2: In the methods part the authors state that in each experimental group the gender of several participants was missing. It is not entirely clear whether those subjects entered the analysis. If would tend to think that they were excluded. If so please correct the abstract which suggests that the data comprises 149 participants.

Minor Comments:

Introduction / second paragraph: the sentence …However, this relationship was no longer significant if nightmare frequency was statistically controlled, i.e., persons with lucid dreams do also have more often nightmares [cf. 12] and, thus, have poor sleep quality data indicate nightmares are associated with sleep problems [13,14]… is overly lengthy and rather hard to digest. Please rephrase. Introduction / last paragraph: comparted should be compared Methods / measurement instruments: The authors state that …minutes were transformed to obtain decimal numbers… Is that information relevant?

Author Response

Comment 1: We emphasized the research question, that is, does the increased brain activity during lucid dreaming REM sleep interfere with the restorative function of sleep.

Comment 2: We included a the statement that all 149 participants were included in the analyses as we did not need age and gender for testing intra-individual differences (within-subject design).

Minor comments: We edited the long sentence about the nightmare effect on the relationship between lucid dreaming frequency and sleep quality and hope that the meaning is now clearer. We also changed “comparted” and omitted the sentence about how we computed sleep duration.

Reviewer 2 Report

The study presented in the manuscript analyses the impact of lucid dreaming, or, more precisely, dream recall on the subjectively evaluated sleep and daytime functioning parameters. Even though the selected topic is interesting in the way of analysing function of REM sleep, however, the data presented is not adding much information answering this question because of several methodological biases: 1) objective sleep evaluation (e.g., actigraphy, which is less intrussive than polysomnography) is missing; 2) the selected sample already had their expectations about lucid dreaming - this is also discussed by the authors; 3) authors need to control for many other cofactors affecting tiredness and daytime sleepiness (e.g., sleep hygiene, sleep-wake rhythm, commorbodities, emotional status). 
The methodological part and sample description was not presented very clearly. 

Author Response

1) We agree that it would be nice to have actigraphy data to back up the subjectively estimated sleep durations (this topic was included in the discussion). But we also want to emphasize that actigraphy does not replace subjective measures regarding sleep quality or the feeling of being refreshed in the morning. That is, subjective sleep variables are as important as objective sleep measures.

2) As pointed out in the discussion, the findings for the control group with no pressure to increase lucid dream frequency are similar to the findings of the experimental groups. This indicates that the possible “success” bias is relatively small.

3) The advantage of this study is the mixed model approach analyzing intra-individual differences. Interindividual differences, e.g., chronotype, personality, habitual sleep patterns etc. had not affected the results. On the other hand, it would be interesting to include day-to-day measures of mood or bed times and study whether these variables affect the occurrence of lucid dreaming, an understudied area.

Lastly, we are not sure about the comment regarding the methods section, more elaborated suggestions would be helpful.