Sleep and Emotion in Adolescents: A Systematic Review of Studies Using Polysomnography, Actigraphy and Fitbit Data

Abstract

Background

Despite the extensive research on sleep and emotion, there is a notable lack of studies examining the impact of sleep on emotion during adolescence, particularly those that use biomedical devices to measure sleep parameters.

Summary

The primary purpose of this systematic review is to critically examine and synthesise the current research on the impact of sleep parameters (duration of sleep, sleep-onset latency, and sleep debt) measured using three biomedical devices (Polysomnography, Actigraphy, and Fitbit) on emotional experience, emotional reactivity, and emotion-regulation capacities in adolescents. Furthermore, the review sheds light on key insights and gaps within the recent literature. Using the PEO and PRISMA frameworks, five electronic databases (ScienceDirect, Web of Science, Scopus, PubMed, and EBSCO) are searched. Eleven studies meeting the inclusion criteria are assessed through the Medical Education Research Study Quality Instrument (MERSQI) and found to exhibit moderate to high quality. The present study observes that sleep disruption and deprivation are detrimental in three key aspects of emotions in adolescents: emotional experience, emotional reactivity, and emotion-regulation capacities.

Key Message

This systematic review draws attention to the key insights and significant gaps in recent literature on the impact of sleep on emotion in adolescents, a critical period and transitional phase of human development. The review opens up new avenues for exploration, particularly in the design of sleep interventions aimed at fostering emotional well-being in adolescents.

Introduction

Despite the extensive research on sleep and emotion, there is a notable lack of studies examining the impact of sleep on emotion during adolescence, particularly those that use biomedical devices to measure sleep parameters. Adolescence, a transitional phase between childhood and young adulthood, ranging from 10 to 24 years,^{1, 2} is a critical period of development marked by significant changes in physiological, neuropsychological, cognitive, emotional, and socio-cultural domains. ³ This phase is also characterised by changes in the circadian rhythm and sleep system, leading to a reduced duration of sleep.^4–6 Adolescents, comprising around 16% of the global population, ⁷ navigate these changes amid rapid technological and socio-cultural advancements worldwide. ⁸ Furthermore, adolescence is an essential phase of the human lifespan that has a cascading impact on the later developmental trajectory. ⁹ Sleep serves important cognitive and emotional functions, which are mediated by the prefrontal cortex. Restricted sleep in adolescents has been found to result in impairments in major domains of cognitive functioning, such as sustained attention, working memory function, and processing speed^{10, 11} as well as major domains of emotion, for example, emotional experience, emotional reactivity, and emotion regulation. ¹² Emotional functioning is of particular importance, as it influences and guides cognition in a manner that enables adaptive responses to the environment, facilitates the regulation of behaviour, and contributes to well-being. ¹³

Research findings suggest that sleep has restorative effects on various functions in wakeful states, particularly emotional functioning, of which emotion regulation ¹⁴ plays a significant role in the biopsychosocial development of adolescents. ¹⁵ Emotion regulation refers to the process of regulating the occurrence, duration, and intensity of internal states of feeling- and emotion-related physiological processes. ¹⁶ Thus, emotion regulation forms an important mechanism that allows adolescents’ adaptation to the significant changes in various domains. ¹⁷ While the specific strategies and techniques that adolescents use to regulate their emotions are shaped by their caregivers and peers, the ability to use these strategies is observed to be dependent on the quality of their sleep.^{18, 19} Therefore, sleep is one of the priority areas during this transitional phase, as it is instrumental in biopsychosocial development in subsequent stages of life.

Sleep is characterised in terms of both subjective experiences, which are measured using self-report measures (such as questionnaires, sleep diaries, and survey schedules), and objective physiological markers, which are measured using biomedical devices. ²⁰ This systematic review focuses on studies that use biomedical devices to measure sleep parameters in adolescents, considering the limitations of self-report measures in this population.^21–23 To make this systematic review more comprehensive, biomedical devices used as measures of sleep are classified into two broad categories: clinical and commercial (non-clinical) devices. The specific focus of this systematic review is on three of the most frequently used non-invasive biomedical devices for measuring sleep in adolescents, including polysomnography, actigraphy, and Fitbit.

Polysomnography and actigraphy fall under the clinical category, whereas Fitbit falls under the commercial category. Polysomnography is one of the most widely used clinical devices, as it combines information received through monitoring activities of major areas, such as the brain, heart, muscles, and eye movements, to measure sleep parameters with accuracy. However, polysomnography, used in a controlled laboratory or clinical setting, is an expensive device compared to the other two.^{24, 25} Actigraphy, a portable clinical device, is used in controlled laboratory, clinical, and natural settings (i.e., home settings). Actigraphy is more cost-effective compared to polysomnography. ²⁶ Both these devices require professional supervision for monitoring and measuring sleep. Further, the interpretation of sleep parameters measured using these devices also requires technical and professional expertise. Fitbit is a cost-effective commercial device that can be easily integrated into users’ day-to-day lives. The output from Fitbit is easier to monitor and interpret for its users compared to the other two devices.^{27, 28} Considering the principles of sensitivity and specificity, polysomnography and actigraphy are regarded as high-end devices for clinical diagnosis, treatment, and research. Moreover, using biomedical devices to measure sleep is beneficial because they provide information on essential sleep parameters (total sleep time, sleep-onset latency, REM sleep, and number of awakenings) with objectivity, accuracy, and precision, compared to self-report measures. ²⁹

Considering this, the present systematic review aims to answer the question: How does sleep, as measured through biomedical devices, influence emotion in adolescents between the ages of 10 and 24 years? Thus, the primary purpose of this systematic review is to critically examine and synthesise the current research on the impact of sleep parameters (duration of sleep, sleep-onset latency, and sleep debt) measured using three biomedical devices (polysomnography, actigraphy, and Fitbit) on emotional experience, emotional reactivity, and emotion-regulation capacities in adolescents aged 10–24 years. Furthermore, the review sheds light on key insights and gaps within the recent literature.

Method

Study Design

The present systematic review used the PEO (Population, Exposure, and Outcome) framework. ³⁰ The population was defined as adolescents between the ages of 10 and 24 years,^1–4 with no clinical diagnosis of a mental disorder. In this review, exposure involved the characteristics of sleep associated with the quality of sleep measured using two types of biomedical devices (clinical and commercial). The primary outcome of interest encompassed three aspects of emotion: emotional experience, emotional reactivity, and emotion-regulation capacities.

Protocol and Eligibility Criteria

The records obtained using the three components of PEO were screened according to the guidelines prescribed in the Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA). ³¹ Records were included if they (a) involved any biomedical devices (clinical/commercial) to measure sleep parameters or (b) used biomedical devices (clinical/commercial) along with self-report measures (questionnaires, sleep diaries, or survey schedules) to assess quality of sleep among adolescents. Studies were excluded if they:

1. Included interventions for emotion regulation arising as a result of sleep deprivation.

2. Used only questionnaires, sleep diaries, or survey schedules to assess quality of sleep.

3. Involved adolescents diagnosed with a mental disorder.

4. Assessed the relationship between sleep and emotion in a specific situation, for example, COVID-19.

Data Sources and Search Strategies

Relevant empirical research articles were identified using a systematic search across five databases—ScienceDirect, Web of Science, Scopus, PubMed, and EBSCO—from January 2025 to June 2025. Book chapters were excluded from the search document type. The five databases were searched using Boolean search techniques, incorporating both logical operators (AND and OR) and modifiers [‘’, (())] along with wildcards (*). The primary search terms used in this systematic review were: ((‘sleep quality’ OR ‘sleep disturbance’ OR ‘sleep hygiene’ OR ‘sleep deprivation’) AND (‘emotion* regulation’ OR ‘automatic emotion* regulation’ OR ‘affect regulation’ OR ‘emotion* reactivity’) AND (‘adolescent*’ OR ‘teen*’ OR ‘youth’ OR ‘young adult*’ OR ‘secondary school student*’)).

Data Extraction and Selection

A 3-phase approach was followed to select the research articles focusing on sleep and emotions in adolescents. In Phase I, four authors (SAS, SBT, SR, and NS) served as reviewers to select the studies for inclusion in the present systematic review. Initially, the reviewers screened the titles of the studies. In Phase II, the abstracts were read, re-read, reviewed, and selected. In Phase III, the reviewers thoroughly read the full texts of the selected research articles multiple times to assess their eligibility for inclusion in the present systematic review. During the review process, when disagreements arose among the reviewers regarding the inclusion of an article, several rounds of discussion took place to reach a consensus on whether to include or exclude it. Moreover, as the emphasis was on the usage of biomedical devices in measuring sleep parameters in adolescents, the opinion of the third author (GA), being an expert in the field of medical sciences, was invariably obtained before bringing the studies under the purview of the present review.

Initially, 1,078 studies were identified from five electronic databases: ScienceDirect (n = 739), Web of Science (n = 181), Scopus (n = 141), PubMed (n = 14), and EBSCO (n = 3). After removing duplicate records (n = 88), the abstracts of 990 studies underwent a review process by the reviewers. During this review, 858 studies were removed. Thus, 132 studies were retained for evaluation of their full texts. After evaluation of the full texts of 132 studies, 25 studies were selected. These 25 studies underwent a second round of a thorough review process to ensure they met the eligibility criteria. Furthermore, 14 studies did not meet the predefined eligibility criteria. Of these, 11 studies were excluded because they involved participants outside the specified age range, as identified during the initial title and abstract screening. Additionally, three studies were excluded as they did not use a biomedical device as a measure of sleep. Thus, finally, 11 studies were included in the present systematic review. The process of data extraction and selection is presented schematically in Figure I, depicting the PRISMA flow diagram.

Figure 1. The PRISMA Flow Diagram. ³¹ .

Note: *The age range of the adolescent period is defined as varying from 10 to 24 years.

Results

After a thorough review, 11 studies were included for further analysis in this systematic review. Outlines of these 11 studies, including the author and year, country, primary objective, age range of participants in years, sample size, biomedical device used to measure sleep parameters, major findings, and quality assessment scores using MERSQI ³² are presented in Table 1.

Table 1. Description of Research Articles Included in the Systematic Review.

S. No.	Author and Year	Country	Primary Objective	Age Range in Years (Mean, SD)	Sample Size	Biomedical Device Used to Measure Sleep Parameters	Major Findings	MERSQI
1.	Herber et al. (2025)	Germany	To investigate the naturalistic effects of typical sleep over multiple nights on emotional processing, considering both objective and subjective measures	14–21 (17.93, 2.43)	n = 106	Fitbit	Emotion regulation was not associated with sleep parameters measured through biomedical devices	15
2.	Chen et al. (2025)	China	To examine the associations between macro- and micro-structures of sleep with resilience in healthy adolescents	12–18 (15.98, 2.16)	n = 42	Polysomnography	Greater resilience capacity was identified in adolescents with higher fast beta power (24–32 Hz) during REM sleep Greater resilience capacity was associated with longer spindle duration No association between resilience capacity or resilience outcome with slow wave sleep properties	14
3.	Reynolds et al. (2024)	United States	To investigate the impact of sleep extension on emotional and social functioning in adolescents	13–17 (15.8, 1.22)	n = 20	Actigraphy	Greater experience of positive emotions in the sleep extension group during goal-directed social interaction Greater appropriateness and variability in emotion following the sleep extension group	13
4.	Hamilton et al. (2023)	United States	To examine whether objectively- and subjectively-measured sleep characteristics predict next-day suicidal ideation occurrence and intensity through affective reactivity to interpersonal events in young people at high risk for suicide	13–23 (16.59, 2.74)	n = 59	Actigraphy	Next-day affective reactivity to negative interpersonal events was predicted by within-personal fluctuations in sleep duration Increased emotional reactivity to negative interpersonal events following reduced duration of sleep Blunted reactivity to positive interpersonal events following irregularities in sleep timing	12.5
5.	Palmer et al. (2020)	United States	To examine the association between sleep patterns and situation selection in healthy adolescents	13–17 (15.19, 1.23)	n = 54	Actigraphy	Less avoidance of negative situations among adolescents with greater variability in sleep-onset timing Greater avoidance of negative situations among adolescents with longer sleep-onset latency	13
6.	Zhang et al. (2019)	China	To investigate the influence of 24-h sleep deprivation on three commonly used emotion regulation strategies: distraction, reappraisal, and suppression	18.47–21.93 (20 ± 1.7)	n = 51	Actigraphy	Adolescents perceived stimuli as more negative following sleep restriction Distraction and reappraisal strategies of emotion regulation were impaired following sleep deprivation	13.5
7.	Chue et al. (2018)	United States	To examine the role of sleep in the daily affective stress recovery process in adolescents	15–19 (16.62, 0.81)	n = 89	Fitbit	Emotional recovery after high stress was poor following reduced duration of sleep Increased experience of positive affect and decreased experience of negative affect following a greater duration of sleep Decrease in the next-day positive affect was predicted by longer sleep-onset latency and greater sleep debt	12
8.	Reddy et al. (2017)	United States	To test the effects of sleep restriction versus idealised sleep on adolescents’ emotional experience, reactivity, and regulation	13–17 (14.83, 1.36)	n = 42	Actigraphy	Decreased experience of positive affect following sleep restriction Increased anxiety following sleep restriction No alterations in emotional reactivity following sleep restriction No alterations in using cognitive reappraisal strategies following sleep restriction	14.5
9.	Tashjian et al. (2017)	United States	To explore the association between sleep-related alterations in the brain and impulsivity in adolescents	14–18 (16.31, 1.12)	n = 59	Actigraphy	The default mode network function was not influenced by the duration of sleep The default mode network was functionally coupled with the left prefrontal cortex among adolescents with poorer quality of sleep Greater positive associations between quality of sleep and impulsivity were identified among adolescents with weaker Default mode network and prefrontal cortex connectivity	12.5
10.	Zhang et al. (2019)	China	To investigate the impacts of sleep deprivation on the brain network of emotional functioning during a resting state	20 = −1.7	n = 57	Actigraphy	Greater frontal alpha asymmetry in the sleep control group than in the sleep-deprived group Frontal theta/beta ratio was higher in the sleep-deprived group than in the control group	13.5
11.	McMakin et al. (2016)	United States	To examine the impact of restricted sleep on socio-affective functioning in adolescents	Study 1: 11.5–15 (13.33, 0.99) Study 2: 12–15 (14.46, 1.19)	n1 = 48 n2 = 16	Polysomnography	Increased experience of negative affect following sleep restriction Increased negative affective behaviour in conflict situations following sleep restriction	12.5*

Note: *Both the studies (Study 1 & Study 2) received equal MERSQI score, that is, 12.5.

Of these 11 studies, seven were carried out in the United States, three in China, and one in Germany. Four studies used only clinical devices (polysomnography and actigraphy)^33–36; five studies used clinical devices along with questionnaires or sleep diaries,^37–41 one study used only a commercial device (Fitbit), ⁴² and one used a commercial device along with a sleep diary to measure sleep. ⁴³ All studies were published within a 10-year span from 2016 to 2025.

Quality Assessments of Included Studies

Although various methods exist for assessing the quality of research articles, this systematic review employed the Medical Education Research Study Quality Instrument (MERSQI) ³² to evaluate the quality of the included studies. All 11 studies underwent rigorous evaluation by two reviewers (SAS and NS) on the six prescribed criteria of MERSQI. The MERSQI scores are presented in the last column of Table 1. Based on the scores obtained on the MERSQI, a line graph was plotted as depicted in Figure 2.

Figure 2. Quality of Included Research Articles (n = 11) Assessed Through MERSQI.

From Figure 2, it is evident that the study by Herber et al. obtained a score of 15 out of a maximum of 18 on MERSQI. ³²

The 11 studies discussed in this systematic review are categorised under four major themes, focusing on the effect of sleep on four essential aspects of emotion: emotional experience, emotional reactivity, emotion regulation, and neural correlates of emotion regulation.

Effect of Sleep on Emotional Experience

The effect of restricted sleep on socio-affective functioning in adolescents was examined through two studies. ³⁴ In the first study, adolescents were assigned to either the sleep restriction (four hours) or sleep extension (10 hours) conditions. In the second study, timings in the sleep restriction conditions were examined in two consecutive nights. Additionally, adolescents were required to engage in a peer interaction task. Sleep parameters were measured using actigraphy, and affective functioning was assessed using visual analogue scales (self-report measure) and an auditory valence identification task. The experience of negative affect in adolescents was found to be greater following sleep restriction in both studies.

In a study ³⁸ based on a randomised two-group pre-post-test design, the impact of sleep restriction (four hours) and idealised sleep (9.5 hours) on emotional experience, among other parameters, was investigated in 42 adolescents. Sleep parameters were measured using actigraphy. Emotional experience was measured using the PANAS-C, ⁴⁴ and emotional valence and intensity were measured using the Self-Assessment Manikin. ⁴⁵ Adolescents in the sleep-restricted group experienced lower levels of positive affect compared to those in the sleep-idealised group.

Another study investigated the impact of sleep on daily affective stress recovery processes in a sample of 89 adolescents. ⁴³ The parameters of sleep measured using a Fitbit were: sleep-onset latency, total sleep time, and sleep debt. Furthermore, daily stress levels and subjective sleep quality were assessed using a questionnaire. Following a stressful day, greater sleep debt and sleep-onset latency were associated with a lower experience of positive affect in the morning, while higher total sleep time predicted higher positive affect in the morning following a stressful day. Sleep-onset latency predicted higher negative affect in the morning, especially following a day of high stress. Additionally, early sleep onset following a previous day of stress was found to result in reduced spillover of negative affect of the previous day, and negative affect in the morning increased with increased sleep debt in adolescents.

In another study, a between-subjects design was employed to investigate the impact of sleep extension on emotional and social functioning in a sample of 20 adolescents. ³⁹ Sleep parameters were measured using actigraphy. The valence of the emotions was identified using experimental tasks. Adolescents in the sleep extension group reported experiencing greater positive emotions during goal-directed social interactions compared to those in the typical sleep group. Furthermore, adolescents in the sleep extension group demonstrated greater emotional appropriateness and greater emotional variability compared to adolescents in the typical sleep group.

Effect of Sleep on Emotional Reactivity

A study assessed emotional reactivity in terms of the intensity or arousal of experience in adolescents in response to the presentation of negative stimuli (images). ³⁸ The sample of adolescents was divided into a restricted sleep group (total sleep time of four hours after a two-hour delay from their usual sleep time) and an idealised sleep group (going to bed at their usual time and getting a total sleep time of 9.5 hours). Emotional reactivity—the intensity or arousal of emotions—was assessed using a behavioural task. Emotional reactivity did not show a statistically significant difference in the sleep-restricted and idealised groups of adolescents.

Another study employed a single-group post-test-only design to investigate the relationship between sleep and situation selection in a sample of 54 healthy adolescents. ³⁵ Sleep data were collected using actigraphy. Situation selection, understood as an antecedent-focused strategy of emotion regulation, were measured using the Use of Situation Selection questionnaire, ⁴⁶ diary writing based on two items, an open-ended response related to situation selection, and a situation selection task. Emotion dysregulation was assessed using the Difficulties with Emotion Regulation Scale. ⁴⁷ Greater fluctuations in sleep-onset time among adolescents were associated with less avoidance of negative situations. Sleep-onset time, higher mid-sleep point, and longer sleep-onset latency were other parameters of sleep associated with reduced avoidance of negative situations among adolescents.

A longitudinal study was conducted to examine whether emotional reactivity to interpersonal events occurring as a result of sleep disruption may be associated with ideations for suicide in a group of 59 adolescents and young adults at risk for suicide. ³⁷ Sleep parameters were measured using actigraphy. Emotional reactivity to interpersonal events was assessed using existing Ecological Momentary Assessment (EMA) items, in which adolescents reported their experiences of positive or negative interpersonal events. For each endorsed event, adolescents also gave their emotional response using visual analogue scales. Results indicated that within-person fluctuations in sleep duration, particularly shorter durations than usual, predicted higher levels of emotional reactivity the following day. In contrast, sleep timing was not found to be associated with emotional reactivity. Additionally, greater sleep onset was associated with lower emotional reactivity to positive interpersonal events. This association was not observed for the sleep duration parameter. The findings indicated that modification of sleep parameters might assist with affect regulation and, therefore, inform interventions aimed at reducing the occurrence and intensity of suicide ideation in adolescents at risk.

Effect of Sleep on Emotion Regulation

In a study, emotional recovery was assessed through daily diaries, where adolescents reported on their sleep, emotions, and stressful events. ⁴³ The results indicated that emotional recovery after high stress was poor among adolescents with reduced sleep duration. Another study found that emotion-regulation capacities (i.e., the ability to generate statements related to reappraisal and downregulation of negative emotions) were not different between sleep-restricted and sleep-idealised adolescent groups. ³⁸

A cross-sectional study identified the naturalistic effects of typical sleep on emotional processing in 54 adolescents. ⁴² Sleep data were collected using a Fitbit device to calculate four parameters: sleep-onset latency, total sleep time, wake after sleep onset, and sleep efficiency. Sleep parameters were subjectively assessed through the Pittsburgh Sleep Quality Index. ⁴⁸ Emotion regulation was assessed objectively using the heart rate variability index via Varioport II and subjectively using the Difficulties in Emotion Regulation Scale. ⁴⁷ No associations were found between sleep parameters and emotion dysregulation; however, subjective sleep parameters were associated with emotion dysregulation.

Effect of Sleep on Neural Correlates of Emotion Regulation

A cross-sectional study investigated the association between impulsivity, sleep, and neural connectivity in 59 adolescents. ³⁶ The assessed sleep parameters included sleep duration, sleep efficiency, the number of awakenings, and the duration of each awakening. These parameters were measured using actigraphy and fMRI. Sleep efficiency, number of awakenings, and duration of awakenings were combined using principal component analysis to create a single score for sleep quality. Impulsivity was assessed using the UPPS-P Impulsivity Scale. ⁴⁹ Results indicated that sleep quality, but not duration, influenced default mode network (DMN) function. The DMN function was found to be positively coupled with the left prefrontal cortex in individuals with poorer sleep quality. Associations between default mode network-prefrontal cortex (DMN-PFC) regions and sleep quality were found to be significantly related to trait levels of impulsive behaviour. Additionally, DMN connectivity was not affected by the duration of sleep among adolescents. Sleep quality and impulsivity of adolescents were positively associated with their weaker DNM functioning and prefrontal cortex connectivity.

Another study employed a between-subjects design to investigate the extent to which total sleep deprivation (24 hours) affected resting-state emotion processing, as measured by frontal alpha asymmetry and theta/beta ratio, in a group of 54 adolescents. ⁴⁰ Sleep was measured using actigraphy, and emotion regulation was objectively assessed using the electroencephalogram (EEG). Results showed greater frontal alpha symmetry in the sleep control group (adolescents following their normal sleep schedule) compared to the sleep-deprived group. Furthermore, the ratio of power of theta to beta waves in the frontal lobe (frontal theta/beta ratio [TBR]) was higher in adolescents who were sleep deprived than in their well-rested counterparts.

The associations between the micro- and macro-structures of sleep and resilience were understood in a study conducted among 42 adolescents. ³³ Sleep parameters were measured using polysomnography and electroencephalography. Macro-structures assessed included sleep-onset latency, total sleep time, sleep efficiency, wake time after sleep onset (WASO), the duration and percentages of NREM (N1, N2, N3), and REM. Micro-structures assessed included power spectral density in NREM and REM sleep as well as sleep spindle properties. Emotion regulation was assessed through the capacity for resilience and measured using the Resilience Scale for Chinese Adolescents. ⁵⁰ While the association between the macro-structure of sleep and resilience capacity was not significant, in the micro-structures, higher REM fast beta power was found to be positively correlated with resilience capacity. Additionally, a longer spindle duration during NREM sleep was significantly associated with a greater capacity for resilience.

In another study, the effect of sleep on emotion was assessed through pupillary responses to affective stimuli using an auditory valence identification task in adolescents. ³⁴ Pupillary response to negative auditory stimuli in relation to neutral stimuli was found to be greater for the sleep-restricted group. Furthermore, no difference was found between the sleep restriction (four hours) and sleep extension (10 hours) groups in terms of pupillary response to positive emotions in relation to neutral stimuli.

Discussion

The objective of the present systematic review is to identify the effect of sleep parameters (measured using biomedical devices) on emotional experience, emotional reactivity, and emotion-regulation capacities in adolescents aged 10–24 years. Sleep in adolescents is examined in this systematic review through three perspectives: sleep disruption, sleep restriction, and sleep disturbances.

Eleven studies were identified that use clinical and commercial devices (polysomnography, actigraphy, and Fitbit) to measure sleep parameters, while emotion is assessed using both self-report measures and performance tasks. Three relevant parameters of sleep, assessed using biomedical devices (both clinical and commercial) in these studies, include the duration of sleep, sleep-onset latency, and sleep debt.

First, the duration of sleep among adolescents, particularly shorter durations, is associated with a greater overall experience of negative emotions. The experience of negative affect is especially heightened in stressful interpersonal situations following sleep restriction. It has been observed that a reduced duration of sleep among adolescents who typically sleep well is associated with a greater experience of negative affect and heightened affective reactivity compared to those who receive an adequate amount of sleep prescribed for this population.^{37, 40} A reduced duration of sleep also impedes the ability to use emotion-regulation strategies in adolescents.^{34, 41} The trend of these findings is supported by recent studies.^{51, 52} Moreover, extending the duration of sleep by even 60 minutes results in a greater experience of positive emotions, as well as a broader range of emotional experiences in adolescents. ³⁹ According to the broaden-and-build theory, experiencing positive emotions is especially important for adolescents during this critical period of development because it facilitates the broadening of the range of their thoughts and action response tendencies, and also builds long-lasting positive personal resources.^53–55

Second, sleep-onset latency refers to the duration from when a person attempts to sleep (lights out) to when they actually fall asleep. ⁵⁶ A longer sleep-onset latency is associated with lower trait avoidance of negative situations. ³⁵ It also predicts lower experience of positive affect and greater experience of negative affect in the morning following a stressful day. ⁴³ Furthermore, it is observed that sleep-onset latency is associated with lower affective reactivity; that is, longer sleep-onset latency leads to reduced affective responsiveness to positive interpersonal events the following day in adolescents.^{37, 57} Thus, this parameter of sleep plays a significant role in socio-affective functioning in adolescents.

Third, sleep debt or the cumulative loss of sleep over time is associated with decreased next-day positive affect and increased next-day negative affect in adolescents.^{43, 58} An increase in negative emotions, specifically anger, is noted in adolescents with sleep debt. ⁵⁹ Moreover, studies have shown that sleep deprivation affects the perception of stimuli, such that even neutral stimuli may be interpreted negatively. ⁶⁰

In terms of the physiology of sleep, it is important to consider four aspects: (a) specific brain regions, (b) networks of functional connectivity, (c) brain wave markers, and (d) neurotransmitters. Specific brain regions, such as the hypothalamus, play a crucial role in the onset and maintenance of sleep by regulating the circadian sleep–wake cycle, as well as the regulation and manifestation of a range of emotions.^61–63 The hypothalamus, along with the limbic system, allows processing of a variety of emotions. ⁶¹ The amygdala, insula, and cingulate gyrus, essential parts of the limbic system, play a crucial role in detecting emotional stimuli of varying intensities. Studies suggest that the functioning of these areas in adolescents with sleep deprivation is impaired, resulting in inaccuracies in the detection and evaluation of emotion-laden stimuli.^{64, 65} The default mode network (DMN)—a network of brain regions (medial prefrontal cortex, medial and lateral parietal cortex, and temporal lobe) ⁶⁶ that allows functional connectivity between them—is associated with self-referential thinking and introspection, which is usually suppressed when one engages in tasks requiring sustained attention. ⁶⁷ The DMN is found to be positively coupled with the left prefrontal cortex in adolescents with poor sleep quality (measured as a function of sleep efficiency and number and duration of awakenings during sleep), leading to greater impulsive behaviour. Apart from these regions of the brain, it is also important to consider brain wave (beta, alpha, theta, and delta) activity during sleep and its relationship to emotional functioning. The TBR is a specific brainwave marker that indicates an individual’s cognitive control over their emotional information processing and regulation capacities. ⁶⁸ A greater TBR, most often seen among individuals with sleep deprivation, is indicative of poorer emotion processing and regulation.^{41, 68} Furthermore, higher-frequency beta power during REM sleep, previously associated with hyperarousal, is found to be linked to greater resilience capacity in adolescents.^{69, 70} REM sleep is characterised by increased levels of acetylcholine, which facilitates the consolidation of emotional memory. ⁷¹ Sleep deprivation has also been found to cause alterations in dopamine receptor function. ⁷² The overall findings thus indicate that sleep plays a crucial role in terms of emotional experience, emotional reactivity, and emotion regulation.

This review has identified significant gaps in the current body of knowledge regarding the effect of sleep on emotion in adolescents. Very few studies have made clear distinctions between affect, emotions, and mood-related changes in adolescents as a function of sleep. The majority of studies use self-report measures (questionnaire/sleep diary/survey schedules) to assess sleep in adolescents. Moreover, most studies focus on understanding the effect of sleep parameters on negative or positive emotional experiences, rather than the mechanisms underlying emotional regulation, particularly implicit mechanisms. Furthermore, the number of studies examining sleep parameters using biomedical devices in adolescents is few. Clinical devices, such as polysomnography, involve the use of associated equipment (video cameras and microphones) that may interrupt natural sleep patterns and lead to heightened concerns about participants’ privacy, particularly when such equipment is used during sleep in a sensitive research environment, especially for adolescents.^{27, 73} Age-related concerns may also limit the experimental manipulation of sleep duration due to ethical considerations. The use of commercial devices (e.g., Fitbit), although easy to use and cost-effective, has been found to lack reliability and validity in terms of the data they provide. ⁷⁴ Considering the limitations of using polysomnography and Fitbit, the literature indicates that the majority of studies prefer actigraphy as a measure of sleep parameters.

A notable observation is that discrepancies are found in the results obtained using both subjective and objective measures of sleep parameters. In some cases, associations between sleep parameters and emotion domains are identified when biomedical devices are used to measure sleep parameters, but not through self-report measures. Conversely, in other cases, associations are observed when using self-report measures but not through biomedical devices.

Furthermore, while using the MERSQI ³² to assess the quality of the included papers, it was noted that the majority of studies did not explicitly state the validity and reliability of the measures used. Additionally, many studies have also not reported on the sampling institution domain of the MERSQI (i.e., the origin of study participants), which affected the obtained MERSQI ³² scores.

Limitations and Future Directions

Although this systematic review offers valuable insights into the impact of sleep on emotions during adolescence and identifies conceptual and methodological gaps in current research, it has a few limitations. First, the present systematic review includes studies written in the English language only, sourced from five electronic databases: ScienceDirect, Web of Science, Scopus, PubMed, and EBSCO. Exclusion of grey literature (e.g., conference proceedings and government reports) as well as book chapters may have limited the comprehensiveness of the present systematic review. Second, although the MERSQI, a tool developed to evaluate the methodological quality of quantitative studies in medical education research, is used to assess the quality of studies in this research, its application in psychology research may be limited. However, in this systematic review, quality assessments of validity in the MERSQI are evaluated only for the outcome variable, that is, emotion.

Despite these limitations, this systematic review identifies important future directions for research. While it is evident that sleep disturbances adversely impact various aspects of emotional functioning, further research is necessary to understand the underlying mechanisms of this relationship. Ensuring effective sleep management among adolescents amidst a rapidly changing world may serve as a preventive strategy against potential issues in their biopsychosocial functioning resulting from poor emotional regulation. Therefore, it is crucial to explore intervention strategies that integrate healthy sleep habits into the daily routines of adolescents, as this is an essential element in managing their emotions.

Conclusion

Understanding the impact of sleep on emotions in adolescents is crucial because it is a modifiable aspect of daily life that supports a healthy developmental trajectory. Thus, the present study observes that sleep disruption and deprivation are detrimental in three key aspects of emotions in adolescents: emotional experience, emotional reactivity, and emotion-regulation capacities. The findings suggest that sleep extension by even 60 minutes is a potential strategy that protects against adverse effects on the emotional experience, emotional reactivity, and emotion-regulation capacities. The salient strengths of this systematic review include its focus on biomedical devices in examining the effects of sleep on emotion by providing more reliable, accurate, and ecologically valid parameters of sleep during adolescence, a critical period of human development. Moreover, the review opens new avenues for exploration, particularly in the design of sleep interventions aimed at fostering emotional well-being in adolescents.

Abbreviation

DMN: Default mode network

DMN-PFC: Default mode network-pre-frontal cortex

EEG: Electroencephalography

EMA: Ecological momentary assessment

MERSQI: Medical education research study quality instrument

PEO: Population, exposure, outcome

PRISMA: Preferred reporting items for systematic reviews and meta-analysis

NREM: Non-rapid eye movement

REM: Rapid eye movement

TBR: Theta/beta ratio

Authors’ Contribution

SAS conceptualised the review, conducted the search, screened the studies, evaluated the studies for inclusion/exclusion, and drafted the manuscript. SBT screened the studies, evaluated the studies for inclusion/exclusion, contributed to the manuscript, and edited it. GA conducted quality appraisal, contributed to the manuscript, critically reviewed, and edited the manuscript. SR supervised the review, conceptualised and designed the review, screened the studies, evaluated the studies for inclusion or exclusion, drafted, and edited the manuscript. BVP contributed to the manuscript and provided a critical review. NS screened the studies, evaluated the studies for inclusion/exclusion, conducted the quality appraisal, contributed to the manuscript, edited, and proofread it. Every author confirmed the final version of the manuscript before submission.

Statement of Ethics

Not applicable.

Informed Consent

Not applicable.