|Year : 2017 | Volume
| Issue : 1 | Page : 1-7
Sleep problems among adolescents: is there a relation with deliberate self-harm and aggression?
Department of Psychiatry, Faculty of Medicine, Mansoura University, Mansoura, Egypt
|Date of Submission||11-Jan-2016|
|Date of Acceptance||08-Mar-2016|
|Date of Web Publication||22-Feb-2017|
Master degree of Neurology and Psychiatry; May 2006, Mansoura University, MD degree of Psychiatry: Nov, 2011, Mansoura University, Lecturer of Psychiatry, Department of Psychiatry, Mansoura University, Mansoura
Source of Support: None, Conflict of Interest: None
Adequate sleep during adolescence is important for healthy development and proper daytime functioning. Sleep problems are commonly reported in adolescents, with an estimated prevalence between 17 and 45%. Besides, adolescence period is usually associated with various behavioral problems such as aggression and self-harm.
The aim of this study was to evaluate sleep habits and the presence of sleep problems in an Egyptian adolescent sample. Moreover, this study aimed to examine the presence of a relationship between sleep problems and the development of aggression and self-harm among those adolescents.
Patients and methods
A total of 117 adolescents in the preparatory stage participated in this study. Three self-report questionnaires were used, Child and Adolescent Sleep Checklist, the Deliberate Self-Harm Inventory, and the Aggression Scale, for students for assessment of sleep problems, deliberate self-harm (DSH), and aggression, respectively, among those adolescents.
A total of 117 adolescents, 51 (43.6%) male and 66 (56.4%) female, participated in this study; their mean age was 13.85±0.81 years. Bedtime problems and daytime problems are more common among adolescents, with higher scores (8.10±3.99 and 6.56±3.61, respectively). Of those, 36 (30.8%) adolescents had a score of 18 or more, and so they were considered to have sleep problems.
The participated adolescents had score ranging from 3 to 38 in the Aggression Scale, with a mean±SD of 12.36±8.32. A total of 24 (20.5%) adolescents had engaged in self-harm according to the Deliberate Self-Harm Inventory.
Moreover, a significant positive correlation (P<0.001) was found between sleep problems and both DSH and aggressive behaviors among those adolescents.
Bedtime problems and daytime problems were common among the participated adolescents. Moreover, DSH and aggressive behaviors were reported.
This study provides evidence that there is a strong relationship between sleep problems and both DSH and aggressive behaviors among those adolescents. Early detection, diagnosis, and treatment of sleep problems and promoting sleep hygiene will, undoubtedly, improve adolescents’ daily functioning and will have good impact on controlling these annoying behavioral problems.
Keywords: aggression, deliberate self-harm, sleep problems
|How to cite this article:|
Sabri Y. Sleep problems among adolescents: is there a relation with deliberate self-harm and aggression?. Egypt J Psychiatr 2017;38:1-7
|How to cite this URL:|
Sabri Y. Sleep problems among adolescents: is there a relation with deliberate self-harm and aggression?. Egypt J Psychiatr [serial online] 2017 [cited 2021 Aug 2];38:1-7. Available from: http://new.ejpsy.eg.net/text.asp?2017/38/1/1/200713
| Introduction|| |
Adolescence is one of the most critical and unstable periods during human life, as many biological, psychological, and social changes occur during this period (Hildenbrand et al., 2013). Adequate sleep in adolescence is important for healthy development and proper daytime functioning (Short et al., 2013).
Adolescents need between 9 and 10 h of sleep per night. As a comparison, children need between 10 and 11 h, whereas adults need 7–9 h (Moore et al., 2011).
Adolescents may suffer from not only lack of sleeping an adequate number of hours but also lack of good-quality sleep. In fact, the time of release of the sleep hormone, melatonin, is delayed in adolescents due to changes in their biological clock, leading to delayed sleep time (Kim et al., 2015). Nowadays, various activities (e.g. TV watching, electronic gaming, and internet involvement) are also affecting the adolescents’ sleep pattern (Ekinci et al., 2014).
Sleep problems are commonly reported in adolescents, with an estimated prevalence between 17 and 45% (Cortese et al., 2013; Adolescent Sleep Working Group, Committee on Adolescence, and Council on School Health, 2014). In one study, a prevalence as high as 65% in Arabian adolescents was reported (Merdad et al., 2014); further assessment of this issue is urgently needed.
The Diagnostic and statistical manual of mental disorders, 4th ed., text revision (DSM-IV-TR) (American Psychiatric Association, 2000) classified sleep disorders into four categories: primary sleep disorders, sleep disorders due to a general medical condition, sleep disorders related to another mental disorder, and substance-induced sleep disorders.
Primary sleep disorders were subdivided as follows: (a) dyssomnias (primary insomnia, primary hypersomnia, narcolepsy, breathing-related sleep disorder, and circadian rhythm sleep disorders), which are characterized by abnormalities in the amount, quality, or timing of sleep; and (b) parasomnias (sleep walking, nightmare, sleep terrors, and parasomnia not otherwise specified), which are characterized by unusual or undesirable phenomena that occur during sleep or on the threshold of wakefulness.
However, the DSM-V (American Psychiatric Association, 2013) eliminated these delineations to further understanding that most sleep disorders are complex interactions of behavior and biology. The new classification includes 10 sleep disorders: insomnia disorder, hypersomnolence disorder, narcolepsy, breathing-related sleep disorders, circadian rhythm sleep disorders, non-Rapid Eye Movement (REM) sleep arousal disorders, nightmare disorder, REM sleep behavior disorder, restless legs syndrome, and substance or medication-induced sleep disorder.
Sleep disorders can seriously affect the adolescent whole life. Several health-related problems such as smoking, substance abuse, and some cardiovascular and metabolic diseases may also threaten the adolescent’s well-being (Ming et al., 2011). As reported in recent studies, adolescents with sleep problems may experience difficulty in getting up in time for school, irritability, confusion, lack of concentration (Saxvig et al., 2012), and may have a higher probability of symptoms or a diagnosis of depression, anxiety disorder, and other significant behavioral and learning problems (Alfano et al., 2013).
Developmentally, adolescents usually have an impulsive and capricious response to the stresses of growth and maturation (Glenn and Klonsky, 2011).
Research studies on adolescent development have taken efforts to understand the roots of several damaging behaviors such as suicide, eating disorders, substance abuse, sexual problems, delinquency, aggression, and, more recently, self-harm (Mehlum et al., 2014).
Aggression is a common problem among adolescents. The prevalence of exhibiting aggressive behavior by the age of 17 years is estimated to be 30–40% for boys and 16–32% for girls (Dane and Marin, 2014). Aggression is a forceful, goal-directed behavior, ranging from social and verbal aggression to physical aggression. Physical aggression (direct or manifest) includes behaviors that threaten or cause physical harm, such as threats of bodily harm (e.g. hitting or pushing), physical fighting, and violent crimes (Marsee et al., 2011). Social aggression (indirect or relational) involves aggression or harming others through manipulation of interpersonal relationships (e.g. spreading rumors, excluding a peer from a group, and trying or threatening to damage someone’s social standing within a group). Finally, instrumental aggression is a behavior to achieve their immediate goals (Volk et al., 2012).
Children and adolescents may exhibit aggressive behavior against school property, classmates, teachers, and peers, consequently; it is crucial to study the development of aggressive behavior with a view to develop effective prevention and treatment programs (Berkowitz, 2012).
Besides, there is a complicated and often misunderstood phenomenon that is growing among teenagers and adolescents, self-harm; it can be defined as any deliberate, nonsuicidal behavior that inflicts harm on one’s body with the goal of relieving emotional distress (Richardson et al., 2015).
Self-harm has a variety of terms such as self-injury, self-mutilation, and self-abuse. There are many different ways of harming oneself: cutting, scratching, picking scabs or interfering with wound healing, burning, punching self or objects, infecting oneself, inserting objects in body openings, and bruising or breaking bones (Kapur et al., 2013).
The prevalence of nonsuicidal self-injury (NSSI) among adolescents in community-based studies ranges between 16 and 38% (Wilkinson, 2013).
Although the main goal of self-injury is to relieve emotional distress, people still do not understand why individuals self-harm (Young et al., 2014).
In DSM-IV (Berkowitz, 2012), self-harm has been represented under criterion 5 of borderline personality disorder, considering the controversies about diagnosing personality disorders before adulthood and the fact that considering self-harm diagnostic for borderline personality disorder could lead to inappropriate management. NSSI is the deliberate, self-inflicted destruction of body tissue (e.g. cutting or burning) without suicidal intent and for purposes not socially sanctioned. NSSI is included in the DSM-V as a condition requiring further research before consideration as an official diagnosis. The proposed criteria require NSSI incidents on 5 or more days within the past year, with at least one of the following expectations: to seek relief from a negative feeling or cognitive state, to resolve an interpersonal difficulty, or to induce a positive state.
The aim of the present study was to evaluate sleep habits and the presence of sleep problems in an Egyptian adolescent sample. Moreover, this study aimed to examine the presence of a relationship between sleep problems and the development of aggression and self-harm among those adolescents.
| Patients and methods|| |
The study took place during the period from June 2015 to November 2015. Through the first 2 weeks of October, students of the preparatory stage in Delta International Language Schools (Mansoura, Egypt) were asked to join this study. The aim of the study was discussed with the head and the principals of the school who were told clearly that all information that will be obtained from the students will be confidential and will not be shared with their families or teachers; the age and sex of the adolescents were the only personal information needed.
Students were given the choice to participate or withdraw; a few students refused to participate due to lack of interest, personal reasons, or fear of being stigmatized. Students who agreed to participate completed the questionnaires during one teaching period (45 min). A teacher was present to organize the data collection and to ensure confidentiality; research staff could be reached by means of phone by school members when needed; the school was visited twice during the study.
A total of 145 sheets containing the three self-report questionnaires were available at the end of the 2 weeks. A total of 28 sheets were excluded because students drew designs or wrote comments instead of choosing an answer. Finally, 117 students were included in this study.
Child and Adolescent Sleep Checklist (CASC) (Oka et al., 2009) is designed to identify sleep habits and to make a screening of sleep problems among preschoolers, elementary school children, and high school students.
CASC has three versions: parental/caregiver version, which is for all age groups (ages 3–18) and is to be filled out by the caregivers; student version for elementary school (ages 6–12), which is to be filled out by students themselves under the instruction of the examiners − that is, teachers, caregivers, or medical professionals; and student version for high school students (ages 12–18), which is to be filled out by the students without instruction. To enable both cross-sectional and longitudinal studies, all these versions use the same set of questions. Currently available language options are English (international version) and Japanese.
CASC Sleep Disturbance Score is calculated based on the responses to the questions on the second page.
The responses were scored as follows:
- Always: Three points.
- Usually: Two points.
- Occasionally: One point.
- Never: 0 point.
- Do not know: 0 point (for parent version only).
CASC Sleep Disturbance Score=sum of the scores of 24 questions. The score ranges from 0 to 72. Children with CASC Sleep Disturbance Score of 18 or more are considered to have sleep problems.
CASC scores are subdivided into four categories:
- Bedtime problems: Q1–Q6 (six questions).
- Sleep breathing and unstable sleep: Q7–Q12 (six questions).
- Parasomnia and sleep movement: Q13–Q18 (six questions).
- Daytime problem: Q19–Q24 (six questions).
For preparing an Arabic version of CASC, translation, back translation, and validity were carried out through the cooperation of a postgraduate member in the English Language Department, Faculty of Arts, Mansoura University. The reliability was examined using the test–retest method (with 2-week interval) with Cronbach’s α coefficient (0.87) through the cooperation of the Department of Community, Faculty of Medicine, Mansoura University.
The Deliberate Self-Harm Inventory (DSHI) (Gratz, 2001) was designed to measure nonsuicidal deliberate self-harm (DSH); it is a self-report questionnaire that measures frequency, age of onset, duration, date of last occurrence, and severity of 17 types of self-harming behavior. The individual is required to report the relative frequency of each type of behavior on a five-point scale: never, seldom, sometimes, often, and always. The DSHI has adequate internal consistency (a=0.82), temporal reliability (r=0.92), and support for validity. For descriptive purposes, we used the following indexes: frequency − that is, the number of episodes per month (seldom: episodic self-harm; sometimes-to-always: repetitive self-harm); types of self-harming behaviors (e.g. self-cutting, self-burning, etc.); and diversification − that is, occurrence of multiple types of self-harming behaviors measured on a three-level scale (0–1 types: minimum diversification; 2–4: moderate diversification; and 5–11: high diversification).
The Aggression Scale for students
The Aggression Scale is a self-report questionnaire (Orpinas and Frankowski, 2001) for elementary and middle school students that measures the frequency of self-reported aggressive behaviors, which may result in physical or psychological injury to other students − for example, pushing, name-calling, hitting, and/or threatening. The range of internal consistency was 0.87–0.88. The scale consists of 11 questions representing a series of aggressive behaviors. Students are asked to mark with a circle the number of times they engaged in each behavior during the last 7 days (range: 0–6+ times). This scale is scored by adding all responses. Possible range is between 0 and 66 points. Each point represents one aggressive behavior the student reported engaging in during the week before the survey. If four or more items are missing, the score cannot be computed. If three or less items are missing, these values are replaced by the respondent’s average.
For preparing an Arabic version of the DSHI and the Aggression Scale for students, translation and back translation were carried out through the cooperation of a postgraduate member in the English Language Department, Faculty of Arts, Mansoura University.
Data were analyzed using statistical package for the social sciences (SPSS, version 15; SPSS Inc., Chicago, Illinois, USA). Qualitative data were presented as number and percentage. Comparison between groups was made using the χ2-test. Quantitative data were presented as mean±SD. Student’s t-test was used to compare two groups. Pearson’s correlation coefficient was used to test correlation between variables. A P value of less than 0.05 was considered to be statistically significant.
| Results|| |
A total of 117 adolescents, 51 (43.6%) male and 66 (56.4%) female, participated in this study; their mean age was 13.85±0.81 years ([Table 1]).
Bedtime problems and daytime problems were more common among adolescents, with a score of 8.10±3.99 and 6.56±3.61, respectively ([Table 2]). A total of 36 (30.8%) of those adolescents had a score of 18 or more, and thus they were considered to have sleep problems.
The participated adolescents had scores ranging from 3 to 38 in the Aggression Scale, with a mean±SD of 12.36±8.32 ([Table 3]).
|Table 3 Results of Aggression Scale and the Deliberate Self-Harm Inventory|
Click here to view
A total of 24 (20.5%) adolescents had engaged in self-harm behavior according to the DSHI.
[Table 4] highlights a nonsignificant increase in sleep problems among 21 (31.8%) female adolescents compared with 15 (29.4%) male adolescents. As regards frequency of DSH, there was a nonsignificant increase in repetitive DSH among female adolescents. However, the incidence of sticking pins into the skin was significantly high among male adolescents (P=0.004). Moreover, minimum diversification was significantly high among female adolescents (P=0.022). Finally, aggressive behavior was significantly high among male (16.35±9.38) compared with female adolescents (9.27±5.81) (P<0.001).
|Table 4 Sex differences in sleep problems (frequency, types, and diversification of deliberate self-harm and aggression)|
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There was a significant positive correlation (P<0.001) between sleep problems and DSH; the mean incidence of sleep problems among adolescents who reported DSH behavior was 28.63±3.92, and the incidence of sleep problems among non-DSH adolescents was 14.32±5.84 ([Table 5]).
There was a significant positive correlation (P<0.001) between sleep problems and aggression among adolescents ([Table 6]).
| Discussion|| |
The aim of the present study was to evaluate sleep habits and the presence of sleep problems in an Egyptian adolescent sample. Moreover, this study aimed to examine the presence of a relationship between sleep problems and the development of aggression and self-harm among those adolescents. A total of 36 (30.8%) adolescents in this sample were found to have sleep problems. Recent research studies estimated the prevalence of sleep problems among adolescents to be between 17 and 45% (Saxvig et al., 2012; Cortese et al., 2013; Adolescent Sleep Working Group, Committee on Adolescence, and Council on School Health, 2014). A prevalence as high as 65% was reported (Merdad et al., 2014) in another recent Arabian study (Satti et al., 2015), in which about 25% of the examined sample reported sleep problems. Further assessment of this issue is urgently needed.
Bedtime and daytime problems were found to be more common among adolescents. This is consistent with the findings of recent research studies (Gradisar et al., 2011; Leger et al., 2012; Short et al., 2013), which suggest that total sleep time in adolescents tends to decrease and the timing of sleep tends to be delayed; this pattern seems to be common among high school students, leading to increased daytime sleepiness and to a significant impact on daytime functioning and academic achievement.
In addition, in this study, a nonsignificant increase in sleep problems among female adolescents was present; this difference may be due to the physiological changes of puberty. Significant sex difference was reported in some studies (Huang et al., 2010; Merdad et al., 2014).
As regards DSH, 24 (20.5%) adolescents had engaged in self-harm behavior; a higher prevalence was recorded in other countries (Hawton et al., 2012; Wilkinson, 2013; Franklin et al., 2014). Perhaps, the relatively low prevalence in this study is due to sociocultural and religious effects.
However, in this sample, adolescents also manifested episodic and minimum-to-moderate diversified self-harm behavior.
Greater frequency and diversification of self-harm were associated with female sex; this is in agreement that reported in prior similar study (Ferrara et al., 2012). Perhaps, girls are more likely to hide unwanted feelings of anger or anxiety.
Besides, this study revealed variable aggressive behavior among adolescents, noticing that male adolescents were more affected compared with female adolescents. This may be due to the effect of the sex hormones and cultural norms of male behavior, and these data were consistent with some recent studies (Dane and Marin, 2014; Sadeghi et al., 2014).
Finally, there is a strong positive correlation between sleep problems and both DSH and aggressive behaviors among those adolescents. These results are supported by recent studies, which reported that sleep problems are correlated positively with aggression (Kamphuis et al., 2012; Pirinen et al., 2014) and self-harm (Hysing et al., 2015) after accounting for other risk factors.
Several hypotheses (Kamphuis et al., 2012) tried to explain the relationship between poor sleep and undesirable behaviors such as aggression and self-harm; sleep problems may result in poor prefrontal cortical functioning, which seems to increase serotonin turnover, hypothalamic–pituitary–adrenal axis dysfunction, and finally individual vulnerability.
| Conclusion|| |
Bedtime problems and daytime problems were common among the participated adolescents. Moreover, DSH and aggressive behaviors were reported. This study provides evidence that there is a strong relationship between sleep problems and both DSH and aggressive behaviors among those adolescents. Early detection, diagnosis, and treatment of sleep problems and promoting sleep hygiene will, undoubtedly, improve adolescents’ daily functioning and will have good impact on controlling these annoying behavioral problems.
The following are recommended:
First, to provide simple guidelines with regard to adequate sleep hygiene to parents and school members. Keeping them informed with up-to-date research studies is the best possible way for introducing healthy sleep habits among adolescents.
Second, to conduct further research with regard to DSH as regards prevalence, psychopathology, and management.
Third, to consider adequate sleep hygiene a milestone in the treatment of behavioral problems such as DSH and aggression.
The sample size was relatively small due to time constraints and limited resources, and so further assessment with larger samples is needed.
Moreover, all data collected were derived from self-reported questionnaires, which might have affected the results. In addition, self-evaluation tools may be affected by cognitive biases, including recall bias and erroneous self-perception.
The author thanks Dr Galal Elfar, the Head of Delta International Language Schools (Mansoura, Egypt), Mohamed Hamdey and Mohamed Elreefaeey, the school principals, for their generous contributions in collecting data in this study.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Alfano CA, Reynolds K, Scott N, Dahl RE, Mellman TA (2013). Polysomnographic sleep patterns of non-depressed, non-medicated children with generalized anxiety disorder. J Affect Disord 147(1-3):379–384.
Adolescent Sleep Working Group, Committee on Adolescence, and Council on School Health (2014). School start times for adolescents. Pediatrics 134(3):642–649.
American Psychiatric Association(2000). Diagnostic and statistical manual of mental disorders. 4th ed. Washington, DC: American Psychiatric Press.
American Psychiatric Association (2013). Diagnostic and statistical manual of mental disorders. 5th ed. Washington, DC: American Psychiatric Press.
Berkowitz L (2012). A different view of anger: the cognitive-neoassociation conception of the relation of anger to aggression. Aggress Behav 38(4):322–333.
Cortese S, Brown TE, Corkum P, Gruber R, O’Brien LM, Stein M et al.
(2013). Assessment and management of sleep problems in youths with attention-deficit/hyperactivity disorder. J Am Acad Child Adolesc Psychiatry 52:784–796.
Dane AV, Marin ZA (2014). Overt and relational forms of reactive aggression in adolescents: relations with temperamental reactivity and self-regulation. Pers Individ Dif 60:60–66.
Ekinci O, Celik T, Savaş N, Toros F (2014). Association between internet use and sleep problems in adolescents. Arch Neuropsychiatry 51:122–128.
Ferrara M, Terrinoni A, Williams R (2012). Non-suicidal self-injury (NSSI) in adolescent inpatients: assessing personality features and attitude toward death. Child Adolesc Psychiatry Ment Health 6:12.
Franklin JC, Puzia ME, Lee KM, Prinstein MJ (2014). Low implicit and explicit aversion toward self-cutting stimuli longitudinally predict nonsuicidal self-injury. J Abnorm Psychol 123(2):463–469.
Glenn CR, Klonsky ED (2011). Prospective prediction of nonsuicidal self-injury: a 1-year longitudinal study in young adults. Behav Ther 42(4):751–762.
Gradisar M, Gardner G, Dohnt H (2011). Recent worldwide sleep patterns and problems during adolescence: a review and meta-analysis of age, region, and sleep. Sleep Med 12(2):110–118.
Gratz KL (2001). Measurement of deliberate self-harm: preliminary data on the Deliberate Self-Harm Inventory. J Psychopathol Behav Assess 23:253–263.
Hawton K, Saunders KE, O’Connor RC (2012). Self-harm and suicide in adolescents. Lancet 379(9834):2373–2382.
Hildenbrand AK, Daly BP, Nicholls E, Brooks-Holliday S, Kloss JD. (2013). Increased risk for school violence-related behaviors among adolescents with insufficient sleep. J Sch Health 83(6):408–414.
Huang YS, Wang CH, Guilleminault C (2010). An epidemiologic study of sleep problems among adolescents in North Taiwan. Sleep Med 11(10):1035–1042.
Hysing M, Sivertsen B, Stormark KM, O’Connor RC (2015). Sleep problems and self-harm in adolescence. Br J Psychiatry 207(4):306–312.
Kamphuis J, Meerlo P, Koolhaas JM, Lancel M (2012). Poor sleep as a potential causal factor in aggression and violence. Sleep Med 13(4):327–334.
Kapur N, Cooper J, O’Connor RC, Hawton K (2013). Non-suicidal self-injury v. attempted suicide: new diagnosis or false dichotomy? Br J Psychiatry 202(5):326–328.
Kim JH, Park EC, Lee SG, Yoo KB (2015). Associations between time in bed and suicidal thoughts, plans and attempts in Korean adolescents. BMJ Open 5(9):e008766.
Leger D, Beck F, Richard JB, Godeau E (2012). Total sleep time severely drops during adolescence. PLoS One 7(10):e45204.
Lloyd-Richardson EE, Lewis SP, Whitlock JL, Rodham K, Schatten HT (2015). Research with adolescents who engage in non-suicidal self-injury: ethical considerations and challenges. Child Adolesc Psychiatry Ment Health 9:37.
Marsee MA, Barry CT, Childs KK, Frick PJ, Kimonis ER, Muñoz LC et al.
(2011). Assessing the forms and functions of aggression using self-report: factor structure and invariance of the Peer Conflict Scale in youths. Psychol Assess 23(3):792–804.
Mehlum L, Tørmoen AJ, Ramberg M, Haga E, Diep LM, Laberg S et al.
(2014). Dialectical behavior therapy for adolescents with repeated suicidal and self-harming behavior: a randomized trial. J Am Acad Child Adolesc Psychiatry 53(10):1082–1091.
Merdad RA, Merdad LA, Nassif RA, El-Derwi D, Wali SO (2014). Sleep habits in adolescents of Saudi Arabia; distinct patterns and extreme sleep schedules. Sleep Med 15(11):1370–1378.
Ming X, Koransky R, Kang V, Buchman S, Sarris CE, Wagner GC (2011). Sleep insufficiency, sleep health problems and performance in high school students. Clin Med Insights Circ Respir Pulm Med 5:71–79.
Moore M, Kirchner HL, Drotar D, Johnson N, Rosen C, Redline S (2011). Correlates of adolescent sleep time and variability in sleep time: the role of individual and health related characteristics. Sleep Med 12(3):239–245.
Oka Y, Horiuchi F, Tanigawa T, Kawabe K, Okada F, Ueno S (2009). Development of a new sleep screening questionnaire: Child and Adolescent Sleep Checklist (CASC). Jpn J Sleep Med 3(2):404–408.
Orpinas P, Frankowski R (2001). The aggression scale: a self report measure of aggressive behavior for young adolescents. J Early Adolesc 21(1):51–68.
Pirinen T, Kolho KL, Ashorn M, Aronen ET (2014). Sleep and emotional and behavioral symptoms in adolescents with inflammatory bowel disease. Sleep Disord 2014:379450.
Sadeghi S, Farajzadegan Z, Kelishadi R, Heidari K (2014). Aggression and violence among Iranian adolescents and youth: a 10-year systematic review. Int J Prev Med 5:83–96.
Satti G, Alsaaid H, Nabil N, Saeed A, Al Hamdan N, El-bakri N (2015). The prevalence of sleep problems and its impact on sleep quality and academic performance. Merit Res J Educ Rev 3(2):126–131.
Saxvig IW, Pallesen S, Wilhelmsen-Langeland A, Molde H, Bjorvatn B (2012). Prevalence and correlates of delayed sleep phase in high school students. Sleep Med 13(2):193–199.
Short MA, Gradisar M, Gill J, Camfferman D (2013). Identifying adolescent sleep problems. PLoS One 8(9):e75301.
Volk AA, Camilleri JA, Dane AV, Marini ZA (2012). Is adolescent bullying an evolutionary adaptation? Aggress Behav 38(3):222–238.
Wilkinson P. (2013). Non-suicidal self-injury. Eur Child Adolesc Psychiatry 22:75.
Young R, Sproeber N, Groschwitz RC, Preiss M, Plener PL (2014). Why alternative teenagers self-harm: exploring the link between non-suicidal self-injury, attempted suicide and adolescent identity. BMC Psychiatry 14:137.
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]