skip to main content


Pzizz is Clinically Proven to Help You Sleep

Academic researchers find Pzizz more effective at improving sleep quality than traditional relaxation music

Posted on April 02 2020

Evidence from studies show music improves sleep in multiple ways (even for clinical insomniacs!). This is not just true in individual experiments, it has also been demonstrated in a large body of scientific research.

Music isn’t the only thing. Hypnosis and progressive relaxation have also been shown to be effective for improving sleep quality and increasing deep sleep (also known as slow wave sleep).

Part of the magic of Pzizz is that we combine all these aspects and more. But does it really work?

Some university sleep scientists wanted to find out. So they conducted a randomized, controlled, blinded, and longitudinal experiment.

The results were fairly clear: Pzizz was more effective at improving sleep quality than traditional relaxation music.

For an in-depth analysis of the study, see below. Additionally:

Pzizz Researcher Write-Up

French, L., Newman, E. J., Hayward, S., Polaschek, D. L. L., & Garry, M. (2008). A napping soundtrack can enhance well-being more than traditional relaxation soundtracks. Cognitive Technology, 13(1), 27–33.


Humans are fairly unique in that we persist in behaviors that lead to irregular and disturbed sleep. For instance, a sample of U.S. adults reported that the majority went without sufficient sleep. This is worrisome given the overwhelming amount of research that indicates that sleep is vital for health and cognitive function, especially memory.

Poor sleep quality has also been shown to be connected to mental health distress. More than 80,000 people were surveyed about sleep patterns, and the results indicated that inadequate sleep for about fourteen days is linked to decreased general health and increased feelings of distress, pain, depression, and anxiety.

There is good news, napping may ameliorate some of the negative effects of inadequate sleep. In one study, a ten-minute nap was shown to increase alertness and cognitive performance, and these effects persisted. Thirty minute naps had more paradoxical effects; While alertness and cognitive performance did eventually improve, both initially decreased after the longer naps (this is what we experience as ‘grogginess’). Some fear that napping will interfere with normal sleep patterns, although this has been shown to be a misconception.

Current Study

Psychologist from the University of Wellington wanted to test if Pzizz was more effective than other commercially available relaxation soundtracks. These researchers asked people to come into the lab for 20-minute naps during the workday. Half the participants listened to a randomly generated Pzizz dreamscape, and the other half listened to one of the commercially available relaxation soundtracks. Those not listening to Pzizz were further split in half. Some listened to the same track every time, the others listened to five different tracks (repeated a week apart). The purpose of this ‘other-repeat condition’ was to control for the fact that each Pzizz dreamscape is different.

Thirteen men and sixteen women were recruited from adverts around the university campus. They ranged from 19 to 55 years old. “Subjects came to ten half-hour sessions at the same time each day, from Monday to Friday, for two weeks. They were allowed to miss one of the ten sessions. Upon completion they were given a $75 value grocery voucher. They were told not to listen to other relaxation soundtracks and to avoid additional naps. The other soundtracks were selected from the US iTunes store. They were all marketed for deep relaxation. Some were slightly shorter then twenty minutes, and so were looped, others extended past twenty minutes, and were cut short by the limited duration of the nap period.

The Pzizz soundtrack was generated for 20-minutes with narration all the way through, and volume for both voice and music set at the half the maximum. Those in the Pzizz condition all listened to the same ten tracks in the same order.

Participants chose a time that fit with their schedules. They would come into a windowless room, which was set-up with armchairs in cubicles for napping; the cubicles and arm chairs were set up so that participants could not see anyone, but the experimenter could monitor the participants. To control for expectancy effect, all participants were told they would be hearing a napping soundtrack produced by new software.

Participants in each time group were randomly assigned to their condition. Participants were instructed to silence any devices that might make sounds, not to talk during the sessions, and not to talk to anyone about the study.

They were given a survey before and after the nap. All surveys were identical, and asked questions regarding 19 dimensions selected from Pzizz’s own promotional material. Thus, the researchers were clinically testing Pzizz on its advertising claims.

These questions included some general measures of well-being. For example, one question asked “how much energy do you have?” Answers were given on a five-point scale, the corresponding answers to the example question were 1 “very little energy” and 5 “a great deal of energy. Other questions listed statements like “I slept well last night” with the numbered answers indicating the degree to which the participant agreed with the above statement.

The experimenter went around the room, starting the soundtracks, checking with participants that they were playing properly, and dimming the lights. After twenty minutes, the experimenter announced the time was up, turned on the lights, and subjects removed their headphones. They then took the same survey again.


There were no significant differences between the two traditional relaxation soundtrack groups.

Well-being measures increased over time; these improvements were greater for those listening to Pzizz. These results were significant only for week two, indicating that Pzizz is superior over time.

Statistical significance was determined by the results being most likely not by chance, the measure of this is known as P-value. The cutoff for the P-Value in psychology is normally around .05, meaning that if this study was repeated one hundred times, the result would probably appear five times out of a hundred or one out of every twenty times. However, these results reached a value of .01 meaning there is a 1% chance these results were by chance, and thus would only appear one in a hundred times (in a statistically perfect world).

Additionally, another statistical measure is Cohen’s d, which shows the size of the differences between groups. A difference can most likely not be by chance, and yet still be very small, and not useful. However, Cohen’s d shows the actual percentage of the difference and overlap between two variables. In this study, Cohen’s d was large, indicating a clinically useful difference between conditions.

“Data also suggest that the Pzizz napping soundtrack produced an additional increment in well-being, both prior to and immediately after sessions… Recall that we found no differences between our “other-repeat” and “other-rotate” conditions. This result suggests that it cannot be simply the novelty of the Pzizz tracks that afforded those subjects a better outcome — there must be something extra involved in Pzizz that contributed to the more positive result.”


One possible limitation of this study is that no direct measure of sleep was taken. However, given the small number of participants, and the direct observation, it seems unlikely that any participant falsely reported sleeping. Another limitation is the small sample size.


This article was published by qualified researchers, from a research university and meets the methodological standards of a clinical experiment.


What we already knew

What this Paper Adds

Further Readings

  • Progressive and Hypnotic Relaxation Can Help You Fall Asleep Faster — Controlled Investigation of Progressive and Hypnotic Relaxation on Insomnia shows statistically significant impact in falling asleep faster
  • Hypnosis Can Increase Deep Sleep— Controlled and blinded experiments using EEG show increase in deep sleep in suggestible women after listening to specific hypnotic suggestions
  • Music Helps Clinical Insomniacs — Music improves sleep quality according to self-reports of people with chronic insomnia. Additionally, music decreased time in Stage 2 and increased REM sleep.
  • Music Improves Sleep — Meta-analysis shows that music’s effect on sleep quality is large enough to be practically and clinically useful, and comes without side-effects.
  • The Science behind Pzizz — A look at what goes on behind the scenes to create one of the most popular sleep apps in the world

Ready to Improve Your Sleep?

Try Pzizz. We design soothing audio that’s clinically proven to help you get better rest. Available on iOS and Android.