Depression and anxiety as mediators of the relationship between sleep disturbance and somatic symptoms among adolescents on a psychiatric inpatient unit

Abstract

Background: This study investigated the relationship between sleep disturbance and somatic symptoms among adolescents residing on a psychiatric inpatient unit. Given the evidence that sleep disturbance may precede the onset of depression and anxiety and the clear associations between mood and somatic symptoms, depression and anxiety were considered as potential mediators of this relationship. Gender was tested as a potential moderator of the relationship between sleep disturbance and depression and anxiety, respectively. Method: A convenience sample of 83 adolescents completed a packet of self-report measures after admission to the unit. Measures assessed depression, sleep disturbance, anxiety, and somatic symptoms. Mediation and moderation analyses were conducted using SPSS PROCESS macro. Results: With anxiety included as a covariate, the overall indirect effect of sleep disturbance on somatic symptoms through depression was significant. No significant moderation effects were found, although females reported significantly higher levels of sleep disturbance, depression, anxiety, and somatic symptoms than males. Conclusions: Results indicated that depression mediated the relationship between sleep disturbance and somatic symptoms above and beyond the effects of anxiety. These findings suggest that interventions aimed at reducing the negative effects of sleep disturbance should also target mood in this population. Individual differences including gender should be considered when developing interventions.

Keywords

Adolescent inpatient sleep somatic symptoms depression anxiety gender

Introduction

Sleep disturbance is common across psychiatric disorders and frequently associated with somatic symptoms (Brand & Kirov, 2011; Zhang et al., 2012). In adolescents with psychiatric illness, evidence suggests a complex relationship whereby ongoing sleep disturbance worsens both psychiatric and somatic symptoms (Brand and Kirov, 2011). Relatively little is known about the relationship between sleep and somatic symptoms among adolescents hospitalized with severe psychiatric symptoms. Research with adults residing on an inpatient unit found that greater self-reported sleep disturbance was associated with greater somatic symptom severity (Strainge et al., 2019) and that improvements to sleep quality predicted significant reduction in somatic symptoms (Madan et al., 2016). Understanding the relationship between sleep and somatic symptoms among adolescents residing on an inpatient unit has important clinical implications for treatment efficacy given their frequent comorbidity with psychiatric conditions.

Possible mediators of the relationship between sleep disturbance and somatic symptoms in adolescence include depression and anxiety. Incidence of depression and anxiety is higher in adolescence than in adulthood and childhood, with evidence suggesting that sleep disturbance plays a key role in the development and severity of these disorders (Brand and Kirov, 2011). Epidemiological studies among adolescents have found that sleep disturbance is associated with concurrent depressive symptoms and predicts vulnerability for depression prospectively (Goldstone et al., 2020). This relationship may be particularly strong among females, who tend to be at greater risk for depression than males (Mojtabai et al., 2016).

Depression is also frequently associated with somatic symptoms (Bohman et al., 2010). Adolescents with depression referred for psychiatric treatment reported significantly greater somatic symptoms than individuals with other diagnoses (Masi et al., 2000). In a community-based sample of Swedish adolescents, duration and severity of depressive symptoms were associated with greater somatic symptoms (Bohman et al., 2010). Prospective studies found that somatic symptoms independent of depression in adolescence predicted incidence of depression and other mood disorders in adulthood (Bohman et al., 2012, 2018). However, other studies have not found support for the predictive nature of the relationship (Dhossche et al., 2001). Thus, the directionality of the relationship between depression and somatic symptoms remains unclear.

The relationships of sleep disturbance and somatic symptoms with anxiety among adolescents also merit exploration, particularly with elevated risk of anxiety during this developmental phase. Incidence of anxiety disorders in a community-based adolescent sample have ranged from .9% (Generalized anxiety disorder) to 16.3% (Specific phobia; Kessler et al., 2012). Similar to depression, sleep disturbance frequently co-occurs with anxiety and predicts more severe anxious symptoms (Brand and Kirov, 2011; Brown et al., 2018). Up to 88% of adolescents with an anxiety disorder may also experience sleep problems, most commonly insomnia (Alfano et al., 2007). There is also evidence to suggest sleep disturbance may be a precursor to anxiety within pediatric samples (Leahy & Gradisar, 2012), with subsequent research demonstrating a unidirectional relationship between shorter sleep duration and onset of anxiety (Roberts & Duong, 2017). However, other cross-sectional research suggests anxiety disorders may precede the onset of insomnia (Johnson et al., 2006). Overall, evidence for the directionality of the relationship between sleep and anxiety remains unclear (see Brown et al., 2018 for a review).

Anxiety disorders are associated with somatic symptoms among adolescents, similar to associations observed with depression (Masi et al., 2000). Adolescents with anxiety disorders tend to have an elevated prevalence of somatic symptoms, and this comorbidity is often associated with more severe anxiety symptoms (Ginsburg et al., 2006). However, while a prospective study found cross-sectional associations between anxiety and somatic symptoms during adolescence, somatic symptoms in adolescence did not predict anxiety disorders in adulthood (Dhossche et al., 2001). Overall, findings regarding the directionality of the relationships of depression and anxiety with somatic symptoms are mixed and further research is necessary to elucidate relationships.

Gender differences exist in the prevalence of psychiatric disorders, symptom patterns, and illness course, and it is possible that gender differences may extend to relationships among sleep, somatic symptoms, depression, and anxiety. Previous literature suggests that the relationship between sleep disturbance and depression in adolescents may be moderated by gender. Specifically, multiple studies have found stronger associations between sleep quality and affective distress among female versus male adolescents (Conklin et al., 2018; van Zundert et al., 2015). While these findings strongly suggest the presence of a gender effect, other studies have not found similar effects. For instance, there was a nonsignificant effect of gender on the relationship between persistent sleep disturbance and depression levels post-treatment among adolescents with depression (Manglick et al., 2013). To our knowledge, this relationship has yet to be studied in a sample of adolescents residing on an inpatient unit.

There is a dearth of literature on the relationship between sleep disturbance and anxiety in adolescents, and only a few studies have examined the role of gender. Similar to the literature regarding sleep and depression, studies to date suggest that the relationship between sleep disturbance and anxiety is stronger for girls than boys. For example, in a study of sleep deprivation on depression and anxiety in a sample of healthy Australian adolescents, one night of total sleep deprivation led to increased levels of anxiety and depression among females only (Short & Louca, 2015). Conversely, other studies have failed to detect a significant effect of gender on the relationship between sleep problems and anxiety among a community sample of children and adolescents (Alfano et al., 2009). Further research is needed to elucidate this relationship in adolescents (Brand and Kirov, 2011).

The aim of the present study was to determine whether depression and anxiety mediate the relationship between sleep disturbance and somatic symptoms among adolescents residing on a psychiatric inpatient unit. Given the high rates of sleep disturbance among adolescents with mental illness, and the frequent exacerbation of sleep problems during inpatient hospitalization (Miller et al., 2019), a more in-depth understanding of the impact of poor sleep on adolescents’ mental and physical health outcomes during a psychiatric inpatient stay may have significant implications for treatment. We hypothesized that depression would mediate the relationship between sleep disturbance and somatic symptoms, controlling for anxiety, such that individuals with greater sleep disturbance would experience more severe somatic symptoms because of increased depression. Similarly, we hypothesized that anxiety would mediate the relationship between sleep disturbance and somatic symptoms, controlling for depression, such that individuals with greater sleep disturbance would experience more severe somatic symptoms because of increased anxiety.

Furthermore, we were interested in the potential moderating role of gender in the relationship between sleep disturbance and depression. We hypothesized that gender would moderate this relationship such that the relationship would be stronger for girls than boys.

Methods

Participants and procedures

Baseline data was collected from a convenience sample of 83 adolescents recruited from the adolescent inpatient unit of a private psychiatric hospital in the northeastern region of the United States as part of a larger longitudinal study. During recruitment, visiting parents and guardians were asked to provide consent. Study researchers introduced the study procedures to eligible adolescents, and adolescents were enrolled in the study if they also provided assent. Eligible adolescents were between ages 12 and 17, had a parent or guardian available during visitation hours to provide written consent, were deemed appropriate for the study by hospital staff, gave written assent of their participation, and were able to complete the self-report measures independently and in one sitting. Procedures were IRB-approved by the research institution and the psychiatric hospital.

Measures

Depression

The Patient Health Questionnaire (PHQ-9) is a 9- item self-report measure of depression severity that correspond to the DSM criteria for a major depressive episode (Kroenke et al., 2001). Participants rate how often they are by bothered by each symptom over a two-week period on a scale from 0 “Not at all” to 3 “Nearly every day”. The PHQ-9 has demonstrated good reliability (α = .87) and construct validity (r = .80) in a psychiatric sample (Beard et al., 2016). It has been validated for use in adolescent samples (Allgajer et al., 2012; Richardson et al., 2010). Internal consistency in the present sample was excellent (α = .92).

Anxiety

The DSM-5 Level 2-Anxiety-Child Age 11–17 is a 13-item self-report measure of anxiety severity for adolescents constructed from the PROMIS pediatric anxiety symptom item bank (PROMIS Health Organization, 2012a). Participants rate how often they were bothered by 13 symptoms in the past week on a scale of 1 “Never” to 5 “Almost Always”. The PROMIS pediatric anxiety symptom item bank has good construct validity and reliability (reliability coefficient of .85) (Irwin et al., 2010). Internal consistency in the present sample was excellent (α = .94).

Somatic symptoms

The DSM-5 Level 2-Somatic Symptom-Child Age 11–17 is a 13-item self-report measure of somatic symptom severity adapted from the Patient Health Questionnaire Physical Symptoms (PHQ-15) (Kroenke et al., 2002) for use with children ages 11–17. Participants rate how often they were bothered by symptoms over the past week on a scale of 0 “Not bothered at all” to 2 “Bothered a lot”. The PHQ-15 has been used in various clinical samples and has been found to have good reliability and validity (Kroenke et al., 2002; van Ravesteijn et al., 2009). Additionally, the PHQ-15 has been used in adolescent samples (Freyler et al., 2013; Zhang et al., 2015). Internal consistency in the present sample was very good (α = .85).

Sleep disturbance

The DSM-5 Level 2-Sleep Disturbance- Child Age 11–17 is a version of the PROMIS- Sleep Disturbance- Short Form (PROMIS Health Organization, 2012b) intended for use with children and adolescents. Participants rate items describing their sleep during the past week on a 5-point Likert scale. The 8-item measure was constructed from the PROMIS Sleep Disturbance and Sleep-Related Impairment item banks (Buysse et al., 2010). It has demonstrated good reliability and construct validity in adult samples (Yu et al., 2012) and there is preliminary evidence for its validity in adolescent samples (Hanish et al., 2017). Internal consistency in the present sample was excellent (α = .94).

Statistical analyses

Analyses were conducted with IBM SPSS Statistics. When appropriate, prorated scores for depression, anxiety, somatic symptoms, and sleep disturbance were calculated. If a participant was missing too many items to calculate a prorated score for a variable, pairwise deletion was applied. Reliability analyses were used to check for internal consistency of key measures. Models tested indirect effects using 5,000 resamples with the PROCESS macro (Hayes & Rockwood, 2017).

Mediation models were conducted to examine the extent to which depression and anxiety independently account for the relationship between sleep disturbance and somatic symptoms. Two models were tested with sleep disturbance entered as the predictor variable; depression or anxiety, respectively, was entered as the mediator variable, and somatic symptoms was entered as the outcome variable. Models were tested with and without covariates (i.e., anxiety or depression). Patterns of results slightly differed with the inclusion of covariates, so models with and without covariates are reported.

To examine gender differences for primary study variables, independent samples t-tests were conducted. Moderated mediation models were conducted to examine the extent to which the indirect effect of sleep disturbance on somatic symptoms through depression or anxiety is conditioned by gender. Two models were tested with sleep disturbance entered as the predictor variable; depression or anxiety, respectively was entered as the mediator variable, and somatic symptoms was entered as the outcome variable. Gender was entered as a moderator of the association between sleep disturbance and depression/anxiety. Models were tested with and without covariates (i.e., anxiety or depression).

Results

Demographics and descriptive statistics

Overall, 83 adolescent completed study measures and were retained for analyses. Age ranged from 12-17 years with a mean age of 15.11 (SD = 1.36). Most of the sample identified as female and European American. See Table 1 for complete demographics.

Table 1.

Sample demographic characteristics.

Characteristic	n or mean	% or SD
Age (years)	15.11	1.36
Gender
Female	50	60.2
Male	25	30.1
Transgender male	5	6.0
Other	3	3.6
Race/Ethnicity
European American	59	71.1
Black/African American	6	7.2
Hispanic or Latino/a	3	3.6
Asian/Asian American	2	2.4
Native American	2	2.4
Unknown	6	7.2
More than one race/ethnicity	5	6.0
Sexual orientation
Lesbian, gay, or homosexual	6	7.2
Straight or heterosexual	35	42.2
Bisexual	28	33.7
Something else	10	12.0
Don’t know	4	4.8
Highest level of education
6^th Grade	1	1.2
7^th Grade	7	8.4
8^th Grade	16	19.3
9^th Grade	15	18.1
10^th Grade	15	18.1
11^th Grade	12	14.5
12^th Grade	2	2.4
Missing	15	18.1

Participants reported mild sleep disturbance scores (M = 26.75, SD = 8.82), moderate-severe depression levels (M = 15.08, SD = 8.01), moderate anxiety levels (M = 35.89, SD = 14.81), and moderate somatic symptom levels (M = 11.42, SD = 6.54) on average. Although there was some variability across participants regarding days elapsed between admission and recruitment into the study, days since admission was not significantly correlated with the main variables of interest (p > .05) and thus was not included as a covariate.

Correlations

Bivariate correlations were examined to assess simple associations among our primary variables. Somatic symptoms were positively related to sleep disturbance (r = .56, p < .001), depression (r = .70, p < .001), and anxiety (r = .64, p < .001). Sleep disturbance was positively associated with depression (r = .63, p < .001) and anxiety (r = .47, p < .001). Descriptive statistics, Cronbach’s alphas, and bivariate correlations are presented in Table 2.

Table 2.

Means, standard deviations, and bivariate correlations among key study variables.

Measure	1	2	3	4	5	6	7	M	SD	α
1. Somatic symptoms	–							11.42	6.54	.85
2. Sleep disturbance	.56***	–						26.75	8.82	.94
3. Depression	.70***	.63***	–					15.08	8.01	.92
4. Anxiety	.64***	.47***	.78***	–				35.89	14.81	.94
5. Gender^a	−.28*	−.33**	−.37**	−.35**	–
6. Race^b	.10	.08	.10	.11	−.13
7. Sexual orientation^c	−.08	−.21	−.21	−.19	.02	.11
8. Days since admission^d	.10	.00	−.18	−.13	.18	.05	−.10	8.96	40.55

N = 72–83. *p < .05, **p < .01, ***p < .001.

^aGender (1 = male, 0 = female).

^bRace (1 = European American, 0 = not European American).

^cSexual Orientation (1 = straight or heterosexual, 0 = not straight or heterosexual).

^dDays since admission = days elapsed between admission and recruitment into the study.

Mediation

Depression

Greater sleep disturbance was associated with greater depression (b = .58, SE = .08, t (78) = 7.31, p < .001) and greater somatic symptoms (b = .41, SE = .07, t (78) = 5.97, p < .001). When depression was entered in the model, the association between sleep disturbance and somatic symptoms became non-significant (b = .14, SE = .08, t (77) = 1.85, p = .07), whereas depression significantly related to somatic symptoms (b = .47, SE = .08, t (77) = 5.60, p < .001). The overall indirect effect of sleep disturbance on somatic symptoms through depression was .27 (SE = .06), with a 95% bias-corrected confidence interval (CI) of [.17, .39].

When anxiety was included as a covariate, greater sleep disturbance was associated with greater depression (b = .31, SE = .07, t (77) = 4.70, p < .001) and greater somatic symptoms (b = .23, SE = .07, t (77) = 3.44, p = .0009). When depression was entered in the model, the association between sleep disturbance and somatic symptoms became non-significant (b = .14, SE = .07, t (76) = 1.95, p = .05), whereas depression significantly related to somatic symptoms (b = .29, SE = .11, t (76) = 2.51, p = .01; See Figure 1). The overall indirect effect of sleep disturbance on somatic symptoms through depression was .09 (SE = .04), with a 95% bias-corrected CI of [.02, .18].

Figure 1.

Model Illustrating Depression as a Mediator of the Association Between Sleep Disturbance and Somatic Symptoms. Bolded numbers indicate coefficients from model with anxiety as a covariate. *p < .05, **p < .01, ***p < .001.

Anxiety

Greater sleep disturbance was associated with greater anxiety (b = .81, SE = .16, t (79) = 4.89, p < .001) and greater somatic symptoms (b = .41, SE = .07, t (79) = 5.97, p < .001). When anxiety was entered in the model, the association between sleep disturbance and somatic symptoms remained significant (b = .24, SE = .07, t (78) = 3.54, p = .0007), and anxiety significantly related to somatic symptoms (b = .21, SE = .04, t (78) = 5.14, p < .001). The overall indirect effect of sleep disturbance on somatic symptoms through anxiety was .17 (SE = .05), with a 95% bias-corrected CI of [.09, .27].

When depression was included as a covariate, greater sleep disturbance was not significantly associated with anxiety (b = −.03, SE = .15, t (77) = −.20, p = .84) or somatic symptoms (b = .14, SE = .08, t (77) = 1.85, p = .07). When anxiety was entered in the model, the association between sleep disturbance and somatic symptoms remained non-significant (b = .14, SE = .07, t (76) = 1.95, p = .05), whereas anxiety significantly related to greater somatic symptoms (b = .13, SE = .05, t (76) = 2.30, p = .02). The overall indirect effect of sleep disturbance on somatic symptoms through anxiety was not significant, −.004 (SE = .02), with a 95% bias-corrected CI of [-.05, .32].

Gender differences

Females reported higher levels of somatic symptoms (M = 12.85, SD = 5.71) compared to males (M = 9.02, SD = 7.56), t (71) = 2.42, p = .018), higher levels of sleep disturbance (M = 28.60, SD = 8.66) compared to males (M = 22.40, SD = 8.54), t (72) = 2.93, p = .005, higher levels of depression (M = 17.18, SD = 7.01) compared to males (M = 10.82, SD = 8.51), t (71) = 3.39, p = .001, and higher levels of anxiety (M = 39.84, SD = 14.09) compared to males (M = 28.92, SD = 13.56), t (72) = 3.19, p = .002.

Due to the limited sample size of the group, transgender and gender non-binary adolescents were not included in independent samples t-tests. Descriptive mean and standard deviation statistics for key study variables by gender are provided in Table 3.

Table 3.

Means and standard deviations for key study variables by gender.

	Mean (SD)
	Somatic symptoms	Sleep disturbance	Depression	Anxiety
Males	9.02 (7.56)	22.40 (8.54)	10.82 (8.51)	28.92 (13.56)
Females	12.85 (5.71)	28.60 (8.66)	17.18 (7.01)	39.84 (14.09)
Transgender and gender non-binary	10.38 (6.17)	29.00 (6.09)	15.02 (8.11)	33.50 (16.00)

Moderated mediation: Examining gender as a moderator

Overall, for the moderated mediation model including depression, there was no evidence of a significant interaction of sleep disturbance with gender (b = .14, SE = .18, t (68) = .78, p = .44). There was also a non-significant interaction of sleep disturbance with gender for the moderated mediation model including anxiety (b = .06, SE = .36, t (69) = .16, p = .87). The inclusion of depression or anxiety as a covariate did not affect results.

Discussion

The present study examined the relationship between sleep disturbance and somatic symptoms among adolescents residing on an inpatient unit. Consistent with our hypothesis, we found that depression significantly mediated the relationship between sleep disturbance and somatic symptoms after controlling for anxiety. Contrary to our prediction, the relationship between sleep disturbance and depression was not significantly moderated by gender. However, as expected, girls in the sample reported higher levels of both sleep disturbance and depression than boys. Unlike depression, anxiety did not significantly mediate the relationship between sleep disturbance and somatic symptoms after controlling for depression, disproving our original hypothesis. Additionally, although females reported higher levels of both anxiety and sleep disturbance than males, there was no moderating effect of gender on the relationship between sleep disturbance and anxiety.

Previous literature has demonstrated an association between sleep disturbance and somatic symptoms among adolescents with psychiatric conditions (Brand and Kirov, 2011). Our findings extend past research by examining this relationship among a unique sample of adolescents residing on an inpatient unit. While both depression and anxiety contribute to the association between sleep disturbance and somatic symptoms, only depression explains this relationship above and beyond the effects of anxiety. This suggests that depression may play a greater role in the relationship between sleep disturbance and somatic symptoms than anxiety. As such, interventions intended to mitigate the negative mental and physical health consequences of sleep disturbance may benefit from targeting mood. Efforts to improve mood may be particularly impactful for individuals whose mood is significantly more affected by their sleep.

Gender did not emerge as a significant moderator of the relationship between sleep disturbance and depression or anxiety, respectively, consistent with prior research in adolescents with depression (Manglick et al., 2013). We did find that female adolescents residing on an inpatient unit experience greater sleep disturbance, depression, and anxiety than their male counterparts. This finding is consistent with previous studies conducted with outpatient and community samples (Conklin et al., 2018; Short and Louca, 2015). Our study is the first, to our knowledge, to demonstrate significant gender differences in sleep disturbance, depression, and anxiety in a unique sample of adolescents residing on an inpatient unit, which is often challenging to access.

The present findings should be interpreted cautiously considering several limitations. Challenges associated with accessing an inpatient population and our data collection window being curtailed due to the COVID-19 pandemic led to a relatively small sample of adolescents. Although our sample was generally representative of our geographical area of recruitment, findings may be specific to the experience of most US-based White, female adolescents residing on an inpatient unit and may not generalize to diverse groups. Lastly, we used cross-sectional data to test the associations between variables, limiting our ability to draw conclusions about causality (Fairchild & McDaniel, 2017). Our findings suggest that the mediating effect of depression on the relationship between sleep disturbance and somatic symptoms among adolescents residing on an inpatient unit is correlational in nature. Longitudinal study designs are needed to draw conclusions about directionality. Future research would also benefit from a larger, more diverse sample of adolescents that could be followed over time, to allow for a more thorough investigation of individual differences on the relationships between sleep disturbance, depression, anxiety, and somatic symptoms to tailor interventions accordingly.

Implications and contributions

Our study is the first to demonstrate a mediating role of depression in the relationship between sleep disturbance and somatic symptoms in a sample of adolescents residing on an inpatient unit. Our findings suggest the importance of targeting sleep to reduce the burden of mental and physical health symptoms and tailoring interventions to the individual.

Footnotes

Acknowledgments

Thank you to Robin Beauregard for her assistance with onsite data collection for this study. Prior work with this dataset was presented at poster sessions for the American Psychological Association, Journal of Clinical Adolescent and Child Psychology, and the Society of Behavioral Medicine.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Ethical approval

The study protocol was approved by the University of Connecticut (H14-346) and Hartford Healthcare (D-HHC-2019–0100) IRBs. Parents/guardians of adolescents provided written consent and adolescents provided written assent prior to participating in the study.

ORCID iD

Laura E Laumann

Author biographies

Laura E Laumann, MS, is a clinical psychology doctoral candidate at the University of Connecticut completing her predoctoral internship at the Warren Alpert Medical School of Brown University.

Jerin Lee, MS, is a clinical psychology doctoral candidate at the University of Connecticut completing her predoctoral internship at the West Haven VA Medical Center.

Jaime Elizabeth Blackmon, PhD, was formerly a graduate student at the University of Connecticut. She is currently a postdoctoral fellow at VA Maryland Health Care System (VAMHCS) and has accepted a position as a staff psychologist on an SMI residential unit.

Meaghan L Delcourt, MS, is a graduate student in clinical psychology at the University of Connecticut.

Matthew C Sullivan, PhD, is a staff psychologist at Massachusetts General Hospital and member of the faculty at Harvard Medical School, where he works in the Behavioral Medicine Program within the Department of Psychiatry. Dr. Sullivan completed his doctoral training in clinical psychology at the University of Connecticut.

Stacy E Cruess, PhD, is a Clinical Psychologist for Hartford Healthcare Medical Group.

Dean G Cruess, PhD, is a Professor in the Department of Psychological Sciences at the University of Connecticut.

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