Dream Recall/Affect and Cortisol: An Exploratory Study
, Nicholas-Tiberio Economou 1,3, Athina Pappa 2, Eftychia Koukkou 2 and Paschalis Steiropoulos 1,4
Round 1
Reviewer 1 Report
Overall, the data presented in the paper are very interesting. The introduction and the discussion needs quite some work. Also, the statistics.
- Introduction: “The emotional quality of dreams also differs from person to person, as well as from night to night. The processes affecting these phenomena remain obscure, nevertheless, several agents have been proposed to influence dream recall and affect.” No references. I would suggest that the authors clearly state a model how cortisol might affect dream recall and/or dream emotions. E.g., the nightmare model of Levin and Nielsen (2007). Especially regarding dream emotions, one would speculate whether stress levels are related to emotional tone, so I was wondering whether cortisol levels in the evening were related to dream emotions of the dreams next morning. I also missing the introduction of the 24-hrs. cortisol profiles (changes in levels), relation to depression, REM sleep etc.
- Statistical analysis. The authors seems to use simple statistical procedures, but these are not appropriate. They should use a mixed model approach, see: Hess et al. (2020). I would advise to include the evening cortisol levels as well.
- First sentence of the discussion: “In this study, our results point – albeit tentatively - towards better dream recall when cortisol levels are sleep (Figure 1).” I do not understand.
- The saliva cortisol directly after waking up is a problem, as cortisol takes some time to increase, 5 to 20 minutes. This problem should be discussed. I also recommend:
Paul, F., Alpers, G. W., Reinhard, I., & Schredl, M. (2019). Nightmares do result in psychophysiological arousal: A multimeasure ambulatory assessment study. Psychophysiology, 56(7), e13366. https://doi.org/10.1111/psyp.13366
as the paper looks into the differences between emotions and variations across the night.
Author Response
The reviewers raised some excellent points, which we were happy to incorporate into the revised manuscript. A point-by-point reply to each comment is provided below. We take this opportunity to thank the reviewers and editorial staff for their time and consideration.
Reviewer 1
Comment 1:
“Introduction: “The emotional quality of dreams also differs from person to person, as well as from night to night. The processes affecting these phenomena remain obscure, nevertheless, several agents have been proposed to influence dream recall and affect.” No references. I would suggest that the authors clearly state a model how cortisol might affect dream recall and/or dream emotions. E.g., the nightmare model of Levin and Nielsen (2007). Especially regarding dream emotions, one would speculate whether stress levels are related to emotional tone, so I was wondering whether cortisol levels in the evening were related to dream emotions of the dreams next morning. I also missing the introduction of the 24-hrs. cortisol profiles (changes in levels), relation to depression, REM sleep etc.”
Response:
We would like to thank Reviewer #1 for reviewing our manuscript and her/hisfeedback. The appropriate references regarding agents influencing dream recall and affect have been added. We have introduced a possible model which describes how cortisol affects dream recall and content. We have also referred to the circadian pattern of cortisol levels, as well as the possible association between cortisol and depression. We have also described that cortisol levels peak during REM sleep.
Comment 2:
“Statistical analysis. The authors seem to use simple statistical procedures, but these are not appropriate. They should use a mixed model approach, see: Hess et al. (2020). I would advise to include the evening cortisol levels as well.”
Response
We would like to thank Reviewer #1 for his excellent suggestion. After reviewing the work of Hess et al. (2020) we also used a mixed model approach regarding morning cortisol levels, which followed normal distribution. A statistically significant association between morning cortisol levels and dream recall emerged (F(1.570)=7.299, p=0.037, eta2=0.021). Sadly, this approach could not be used for evening cortisol levels, as they do not follow normal distribution.
Comment 3:
“First sentence of the discussion: “In this study, our results point – albeit tentatively - towards better dream recall when cortisol levels are sleep (Figure 1).” I do not understand.”
Response
We would like to thank Reviewer #1 for this comment. We have corrected this editorial error: “In this study, our results point – albeit tentatively - towards better dream recall when cortisol levels are increased before and after sleep.”
Comment 4:
“The saliva cortisol directly after waking up is a problem, as cortisol takes some time to increase, 5 to 20 minutes. This problem should be discussed. I also recommend:
Paul, F., Alpers, G. W., Reinhard, I., &Schredl, M. (2019). Nightmares do result in psychophysiological arousal: A multimeasure ambulatory assessment study. Psychophysiology, 56(7), e13366. https://doi.org/10.1111/psyp.13366
as the paper looks into the differences between emotions and variations across the night.”
Response
We would like to thank Reviewer #1 for this excellent comment. All participants were instructed to provide morning saliva samples 10 minutes after awakening and not immediately after awakening. This misconception has been corrected in the text. We have also reviewed the work of Paul et al (2019) and have referenced their work in our introduction.
Reviewer 2 Report
Dear Authors,
This is very interesting study, but there is a lot of doubts if the results and conclusion will resist future investigations based on polysomnography studies and performed in bigger group of subjects and with the use of more detailed questionnaire regarding the affect related to the dreams. Anyhow, in order to improve the quality of the manuscript avoiding repetition of the same information in the “Introduction” and “Discussion” would be strongly advised. There is small editorial error in the verse 86 (are…sleep)
Author Response
The reviewers raised some excellent points, which we were happy to incorporate into the revised manuscript. A point-by-point reply to each comment is provided below. We take this opportunity to thank the reviewers and editorial staff for their time and consideration.
Reviewer 2
Comment
“Dear Authors,
This is very interesting study, but there is a lot of doubts if the results and conclusion will resist future investigations based on polysomnography studies and performed in bigger group of subjects and with the use of more detailed questionnaire regarding the affect related to the dreams. Anyhow, in order to improve the quality of the manuscript avoiding repetition of the same information in the “Introduction” and “Discussion” would be strongly advised. There is small editorial error in the verse 86 (are…sleep)”
Response
We would like to thank Reviewer #2 for his excellent comments. Studies with larger groups of subjects as well as polysomnography and more detailed questionnaires are necessary for more robust results, indeed. Our study is a pilot study suggesting that cortisol is an important modulator for dream recall and affect, and therefore further study is required. Moreover, we have removed information which is repeated in “Discussion”. We have also corrected the editorial error in the verse 86: “In this study, our results point – albeit tentatively - towards better dream recall when cortisol levels are increased before and after sleep.”
Round 2
Reviewer 1 Report
As the inclusion of the evening cortisol levels are very interesting and really improve the quality of the study, I would suggest to try different tranformations (square root, logarithmic etc.) to normalize the evening cortisol levels and give it a try.
Author Response
Reviewer#1
As the inclusion of the evening cortisol levels are very interesting and really improve the quality of the study, I would suggest to try different tranformations (square root, logarithmic etc.) to normalize the evening cortisol levels and give it a try.
We thank the Reviewer for his/her pertinent comments
We have added the following at the end of the Methods section in the revised version of the manuscript:
"Evening salivary cortisol, even after logarithmic, square root or inverse (1/x) transformation, was not normally distributed throughout; normality of distribution was noted only in the set of values, after inverse (1/x) transformation, from women in the follicular phase. Bearing this caveat, mixed model analysis, with evening salivary cortisol [after inverse (1/x) transformation] as the dependent variable, gender, age and dream recall or affect as the fixed variables and sampling time as the random effects grouping factor was also implemented."
Additionally, we have revised, and added the following at the end of the Results section in the updated version of the manuscript:
"Implementing mixed model analysis, more frequent dream recall was also noted with higher morning salivary cortisol [F(1.570)=7.299, p=0.037, eta2=0.021]; no differences in affect vis-à-vis morning salivary cortisol were noted with this analysis. Moreover, evening salivary cortisol levels [after inverse (1/x) transformation] did not show differences vis-à-vis dream recall or affect with mixed model analysis (all p>0.1)."
Author Response File: 
Author Response.docx
