Research Article - Current Pediatric Research (2018) Volume 22, Issue 3

Anxiety disorders among adolescents attending secondary schools in Enugu South East Nigeria.

¹Department of Community Medicine, Enugu State University Teaching Hospital, Park lane, Enugu.

²Department of Paediatrics, College of Medicine, University of Nigeria, Ituku-Ozalla, Enugu.

³Department of Paediatrics, Federal Teaching Hospital Abakaliki, Ebonyi State.

⁴Department of Paediatrics, Enugu State University Teaching Hospital, Parklane Enugu.

⁵Department of Psychological Medicine, College of Medicine, University of Nigeria, Ituku-Ozalla, Enugu.

⁶Department of Community Medicine, College of Medicine, University of Nigeria, Ituku-Ozalla, Enugu.

Corresponding Author:

Vivian Ozoemena Onukwuli
Consultant Pediatrician, Lecturer, University of Nigeria
University of Nigeria Teaching Hospital (UNTH), Ituku-Ozalla, Enugu State, Nigeria
Tel: 2348034710392
Email: vivianonukwuli@yahoo.com

Accepted date: October 04th, 2018

Abstract

Background: Anxiety disorders in adolescents can lead to serious psychosomatic problems. Objectives: This study was aimed at determining pattern and factors associated with anxiety disorders among adolescents who attend secondary schools in south east Nigeria. Methods: A total of 1500 adolescents who fulfilled the inclusion criteria were enrolled by simple random sampling. The questionnaire used was adapted from The Revised Manifest Anxiety Scale (RCMAS). The RCMAS is a 37-item self-report inventory used to measure anxiety in children, for clinical purposes (diagnosis and treatment evaluation), educational settings, and for research purposes. Results: Three hundred and eighty-four students 384 (34.1%) had anxiety. On segregation into different components of anxiety 188 (16.7%) had physiological component, 674 (59.9%) had worry and 399 (35.5%) had concentration issues. There was statistical significant association between sex and general anxiety (χ2=30.121, p<0.001). There were statistical significant association between sex and physiological component of anxiety (χ2=10.838, p=0.001), class (χ2=5.546, p=0.009), father’s educational level (χ2=8.306, p=0.016) and mother’s occupation (χ2=12.348, p=0.015). There was statistical significant association between sex and worry component of anxiety (χ2=24.403, p<0.001). There was statistical significant association between sex and concentration component of anxiety (χ2=11.223, p=0.001). Conclusions: All the spectrum of anxiety disorders was present among adolescents in their institution with varying degrees of associated factors.

Keywords

Anxiety disorders, Adolescents, Secondary schools, Revised manifest anxiety scale.

Abbreviation

DSM: Diagnostic and Statistical Manual of Mental Disorders; ICD: International Classification of Diseases; NICE: National Institute for Health and Care Excellence; RCMAS: Revised Children’s Manifest Anxiety Scale

Implications and Contribution

Anxiety disorders among adolescents are serious and most neglected mental health problem. In Nigeria, knowledge of mental disorders is extremely low, making it difficult for people to access prompt medical attention.

This study reveals that all the spectrum of anxiety disorders were present among adolescents with associated factors.

Introduction

Anxiety disorders in adolescents occur when anxious feelings are persistently intense, go on for weeks or even longer and are so distressing that they interfere with young people's learning, socializing and ability to carry out day to day activities [1].

Anxiety disorders among adolescents are classified in the Diagnostic and Statistical Manual of Mental Disorders (DSM, currently version V, American Psychiatric Association) or the International Classification of Diseases (ICD, currently version 10, World Health Organization) [2]. According to the DSM-5, anxiety disorders comprise the following conditions: panic disorder, agoraphobia, social anxiety disorder (social phobia), specific phobia, Generalized Anxiety Disorder (GAD), separation anxiety disorder, and selective mutism [2].

Majority of this disorder share common clinical features such as extensive anxiety, physiological anxiety symptoms, and behavioral disturbances such as extreme avoidance of feared objects, and associated distress or impairment [2-4]. There are several variations in the epidemiology of anxiety disorders, however the lifetime prevalence of anxiety disorder in studies with children or adolescents is about 15% to 20%. In fact, it has been opined that the most frequent disorders among children and adolescents are separation anxiety disorder, with estimates of 2.8% and 8%, and specific and social phobias, with rates up to around 10% and 7%, respectively [3-5].

It is pertinent to note that in the assessment of anxiety in children the core diagnostic criteria might present differently among them, requiring special assessment strategies. For instance, the differences in age of onset provide one important scenario for separating different types of anxiety disorders [4-7]. Furthermore, the earliest age of onset has been consistently found for separation anxiety disorder and some types of specific phobias with most cases emerging in childhood before the age of 12 years, this is followed by the onset of social phobia with incidences in late childhood and throughout adolescence, with very few cases emerging after the age of 25. Panic disorder, agoraphobia, and GAD, in contrast, have their core periods for first onset in later adolescence with further first incidences in early adulthood [4]. It is estimated that current prevalence of anxiety ranged between 0.9% and 28.3% and past year prevalence was between 2.4% to 29.8% [4-7]. Substantive factors such as gender, age, culture, conflict and economic status, and urbanization accounted for the greatest proportion of variability [4]. The global current prevalence of anxiety disorders ranged from 5.3% (3.5% - 8.1%) in African cultures to 10.4% (7.0 - 15.5%) in Euro/Anglo cultures [5-8].

Anxiety disorders in adolescents can be serious mental health problems since these young people are still developing. If left untreated, it can have longterm consequences for mental health and development. Generally, all anxiety disorders more frequently occur in females than males. Although sex differences may occur as early as childhood, they increase with age reaching ratios of 2:1 to 3:1 in adolescents [1,6].

Risk factors for anxiety disorders include genetic, personality, environmental or other factors like ongoing physical illness, most anxiety disorders respond well to treatment especially if the disorders are treated early [8].

In Nigeria, awareness and knowledge of mental disorders is extremely low, making it difficult for people to access adequate and prompt medical attention [9]. Furthermore, factors such as lack of health facilities, inadequately skilled mental health practitioners and low socioeconomic status increase the number of patients getting proper mental health care.

In order to diagnose and manage anxiety disorders in adolescents promptly and adequately, it is pertinent to know the dynamics of such an important problem in an environment. This paper therefore is a screening tool aimed at determining the pattern and spectrum and prevalence of anxiety disorders among adolescents attending secondary schools in two states in south east Nigeria.

At present, there is a dearth of knowledge on adolescent anxiety disorders in the study locality, thus justifying the need for this study.

Methods

Study design

This is an observational cross-sectional study that examines various types of anxiety disorders among adolescents aged 11-20 years that attend secondary school in Enugu and Ebonyi states, south East, Nigeria. It is important to note that the study was conducted in an exam free period. This is because exam in itself is anxiety provoking.

Study area

The study was carried out among adolescents in four secondary schools in Enugu and Ebonyi states of Nigeria.

Study population

One thousand five hundred adolescents who gave consent and who met the inclusion criteria were consecutively recruited between April and June, 2017 from four schools located in urban and semi urban areas of the states. The schools were selected by convenient sampling. One thousand five hundred questionnaires were administered but 1450 were eventually studied. This gave a response rate of 94%. About 500 questionnaires were filled by respondents from Ebonyi state while 1000 were filled by respondents from Enugu state.

Study procedure

The study was carried out among adolescents in JS 1 and JS 2, SS 1and SS 2 because those in JS 3 and SS 3 were either preparing or writing their certificate examinations at that period senior secondary 4 to 6. Informed consent was sought from the students after they were told that their participation was optional and that they could withdraw from the study at any time, if they so desire. Adolescents who gave consent and who are within the age range of 11- 20 years were included in this study while those without consent and those with suspected psychiatric disorders who were on antipsychotic drugs were excluded. (This was elicited by asking or interviewing the subjects to find out if they had been at any time diagnosed of any psychiatric illness or received antipsychotic drugs). Socioeconomic class was assigned to the students using a recommended method [8].

Questionnaire

The questionnaire was adapted from The Revised Children’s Manifest Anxiety Scale (RCMAS).

The RCMAS is a 37-item self-report inventory used to measure anxiety in children, for clinical purposes (diagnosis and treatment evaluation), educational settings, and for research purposes. The RCMAS consists of 28 Anxiety items and 9 Lie (social desirability) items. Each item is purported to embody a feeling or action that reflects an aspect of anxiety, hence the subtitle, “What I think and Feel”. It is a relatively brief instrument, which has been subjected to extensive study to ensure that it is psychometrically sound.

The Revised Children’s Manifest Anxiety Scale was developed by Reynolds et al. [9]. It is based on the Children’s Manifest Anxiety Scale (CMAS). The Revised version of the CMAS deletes, adds and reorders items from the CMAS to meet psychometric standards. Reynolds et al. [9] also renamed the instrument, “What I Think and Feel”, although subsequent papers primarily refer to it as the Revised Children’s Manifest Anxiety Scale (RCMAS) [9].

Reliability

Several types of reliability can be demonstrated with the RCMAS, in terms of the internal consistency of the instrument, stability, and possibly equivalence, but not in terms of the inter-rater reliability. Reynolds and other researchers have focused on developing an instrument that was psychometrically sound and that could be used by a variety of practitioners (clinicians, teachers and researchers), without attention to potential variations with application or interpretation in its use.

Validity

There is substantive research confirming the validity of the RCMAS as a measure of chronic manifest anxiety in children, dating back to the original article reporting the development of the RCMAS. In addition, the RCMAS is frequently used in research to validate other instruments and to measure treatment effects.

A total of 28 anxiety items (25 from the CMAS and three new items), and nine Lie items were retained to form the current 37 items of the RCMAS. The results would suggest that the 28 anxiety items that were finally selected adequately represent all aspects of the anxiety construct, thereby indicating content validity.

The five factors confirmed are as follows [9].

Anxiety Scale Factors:

Item Numbers

The Physiological Factor- 1, 5,

9, 13, 17, 19, 21, 25, 29, 33

The Worry/Oversensitivity Factor- 2, 6,

7, 10, 14, 18, 22, 26, 30, 34, 37

The Concentration Anxiety Factor- 3, 11,

15, 23, 27, 31, 35

Scoring method and interpretations of results

Each item is given a score of one for a “yes” response, yielding a Total Anxiety score (Ag). Three empirically derived Anxiety Subscales scores (Physiological Anxiety, Worry/Oversensitivity, and Social Concerns/ Concentration) and Lie Scale scores can be calculated. The Lie scale is best thought of as a social desirability scale as it does not directly and conclusively detect “lying”.

Stallard, Velleman, Langsford and Baldwin recommend that an overall cut-off point of 19 out of 28 be used to identify children experiencing clinically significant levels of anxiety.

High scores on the sub-scales can represent different aspects of anxiety, which can be used to develop hypotheses about the origin and nature of a child’s anxiety.

1. High scores on the Physiological Factor (items 1, 5, 9, 13, 17, 19, 21, 25, 29, 33) can indicate physiological signs of anxiety (eg sweaty hands, stomach aches).

2. High scores on the Worry/Oversensitivity Factor (items 2, 6, 7, 10, 14, 18, 22, 26, 30, 34, 37) would suggest that the child internalises their experiences of anxiety and that he or she may feel overwhelmed and withdraw.

3. High scores on the Concentration Anxiety Factor (items 3, 11, 15, 23, 27, 31, 35) would suggest that the child is likely to feel that he or she is unable to meet the expectations of other important people, inadequate and unable to concentrate on tasks.

Data Analysis

All data were analyzed using the Statistical Package for Social Sciences program (SPSS version 20 Chicago.) Chi-square was used to test significant association between gender and general, physiological and worry components of anxiety and between social class and general, physiological and worry components of anxiety odd ratio was used to compare social class of parents of adolescents with anxiety and those parents of adolescents with no anxiety. A p-value less than 0.05 was accepted as significant for each statistical test

Ethical Consideration

Ethical clearance was procured from the Ethics Committee of the University Of Nigeria Teaching Hospital Enugu.

Results

Table 1 shows that majority of participants were <18 years 1068 (94.9%), female 644 (57.2%), in senior secondary school 719 (63.9%), their fathers had tertiary education 792 (70.4%), their mothers had tertiary education 820 (72.9%), their father were civil/public servants 448 (39.8%) and their mother were civil/public servants 654 (58.1%).

Table 1: Socio-demographic characteristics of participants

Table 2 shows that 384 (34.1%) had generalized anxiety. On segregation into different components of anxiety 188 (16.7%) had physiological component, 674 (59.9%) had worry and 399 (35.5%) had concentration issues.

Table 2: Associations of characteristics with general anxiety

Table 3 shows that there were statistical significant association between sex and general anxiety (χ²=30.12, p<0.001). There were no statistical significant association between general anxiety and other variables; age (χ²=2.53, p=0.112), class (χ²=2.64, p=0.104), father’s educational level (χ²=3.92, p=0.141), mother’s educational level (χ²=1.10, p=0.577), father’s occupation (χ²=3.43, p=0.489) and mother’s occupation (χ²=8.59, p=0.072).

Table 3: Associations of characteristics with physiological anxiety

It also shows that those aged ≥ 18 years were about 2 times (AOR=1.94, 95% CI 1.11–3.41) likely not to have anxiety than those <18 years. Females were about 2 times (AOR=2.14, 95% CI 1.64–2.78) likely not to have anxiety than males. Those in senior class were about 80% (AOR=0.78, 95% CI 0.59–1.01) likely not to have anxiety than those in junior class. Those whose father had secondary education were about 80% (AOR=0.78, 95% CI 0.44–1.38) likely not to have anxiety than those whose father had primary education and below. Those whose mother were low technical professionals were about 4 times (AOR=3.73, 95% CI 1.40–9.98) likely not to have anxiety than those whose mother were civil/public servants.

Table 4 shows that there were statistical significant association between sex and physiological component of anxiety (χ²=10.84, p=0.001), class (χ²=5.55, p=0.009), father’s educational level (χ²=8.31, p=0.016) and mother’s occupation (χ²=12.35, p=0.015). There were no statistical significant association between physiological component of anxiety and other variables; age (χ²=0.04, p=0.848), mother’s educational level (χ²=3.47, p=0.177), and father’s occupation (χ²=0.74, p=0.946).

Table 4: Associations of characteristics with worry (Anxiety)

It also shows that females were about 2 times (AOR=1.77, 95% CI 1.26–2.48) likely not to have anxiety than males. Those in senior class were about 60% (AOR=0.66, 95% CI 0.48–0.92) likely not to have anxiety than those in junior class. Those whose father had secondary education were about 60% (AOR=0.63, 95% CI 0.29–1.35) likely not to have anxiety than those whose father had primary education and below. Those whose mother had secondary education were about 50% (AOR=0.54, 95% CI 0.26–1.14) likely not to have anxiety than those whose mother had primary education and below. Those whose mother were low technical professionals were about 5 times (AOR=34.76, 95% CI 1.78–12.73) likely not to have anxiety than those whose mother were civil/public servants.

Table 5 shows that there were statistical significant association between sex and worry component of anxiety (χ²=24.403, p<0.001). There were no statistical significant association between worry component of anxiety and other variables; age (χ²=1.325, p=0.250), class (χ²=0.733, p=0.392), father’s educational level (χ²=1.242, p=0.537), mother’s educational level (χ²=0.741, p=0.690), father’s occupation (χ²=1.484, p=0.829) and mother’s occupation (χ²=1.471, p=0.832).

Table 5: Associations of characteristics with concentration (Anxiety)

It also shows that females were about 2 times (AOR=1.84, 95% CI 1.44–2.33) likely not to have anxiety than males.

Table 6 shows that there were statistical significant association between sex and concentration component of anxiety (χ²=11.22, p=0.001). There were no statistical significant association between concentration component of anxiety and other variables; age (χ²=0.63, p=0.429), class (χ²=0.02, p=0.896), father’s educational level (χ²=5.57, p=0.062), mother’s educational level (χ²=3.23, p=0.199), father’s occupation (χ²=5.04, p=0.283) and mother’s occupation (χ²=0.22, p=0.639).

Table 6: Associations of characteristics with concentration (Anxiety)

It also shows that females were about 2 times (AOR=1.5, 95% CI 1.16–1.93) likely not to have anxiety than males. Those whose father had secondary education were about 50% (AOR=0.53, 95% CI 0.30–0.95) likely not to have anxiety than those whose father had primary education and below. Those whose mother had secondary education were about 1.2 (AOR=1.21, 95% CI 0.68–2.16) likely not to have anxiety than those whose mother had primary education and below.

Discussion

We noted in this study that the prevalence of anxiety among adolescents is 34.1 percent. Jalali et al. [10] in their study noted the prevalence to be 10.8%. They obtained this prevalence mainly among those who are between 10- 18 years. Several studies have reported the prevalence of anxiety in adolescents in different part of the world; in fact it ranges between 2.6% to 41.2% among pre-adolescent children to 6.8% and 85% among adolescents [11-14]. Current reviews revealed the prevalence rates of 0.54% to 12.8% for generalized anxiety disorder, this also confirms vividly the prevalence rates of 0.16% to 11.1% obtained in other areas [15-17]. Differences in race, geographical construct and methodology could explain these variations in prevalence.

We noted in this present study varying prevalence in types of anxiety spectrum. For instance, the prevalence of physiological, worries and loss of concentration in adolescents were noted to be 16.7, 59.9 and 35.5% respectively.

Physiologic anxiety which is seen clinically in adolescents as sweaty hands, stomach aches, fear, jitteriness showed a wide prevalence of between 6 and 44 % in adolescents [15].

Moreover, the prevalence of worries or Anxiety Hypersensitivity (AS) was noted to be 59.9% in this study which is the highest type of anxiety seen in adolescents. It is noted that as a risk factor for psychopathology [16]. These findings provide strong evidence suggesting that AS is a risk factor for development of anxiety symptoms and depression among youth in early adolescence.

Schnidt et al. [17] and Zvolensky et al. [18] have opined that there is a clarion call for the use of behavioral skill to significantly reduce AS and this will offer a possibility for the implementation of a primary prevention intervention that can avert anxiety and panic reactions among high-risk youth.

These worries and over sensitivity in adolescents throws much light that an adolescent with this disorder internalizes their experiences of anxiety and that he or she may feel overwhelmed and withdrawn [19].

It is seen in this study that there exists a female predominance in all types of anxiety. In all studies seen, anxiety disorders were almost twice as common among females as compared to males [20,21]. Although sex differences may occur as early as childhood, they increase with age reaching ratios of 2:1 to 3:1 in adolescence [22].

Reasons ranging from biological, genetic, psychosocial, hormonal to family factors have been pointed out as possible cause for this gender difference.

There is a linear increase in prevalence of anxiety from the junior class to the senior class of facing new learning environment and harder and more complex curriculum as their progress to higher class may account for this increase.

We examined three strata of anxiety among adolescents; this is indeed the most commonly used measures of anxiety in children elicited by the Revised Children’s Manifest Anxiety Scale. The subtypes are worry and oversensitivity, physiological anxiety, and social concerns and concentration problems.

We noted a strong link of physiological anxiety among adolescents with high levels of paternal level of education and maternal occupation. There exists no link between other types of anxiety with socioeconomic class. Katie and colleagues, in the USA, noted that parental education is associated with mental disorders only among non- Hispanic White adolescents but pointed that none of the socioeconomic indices is associated with mental disorders in Black adolescents. Many studies have also noted a stronger association between poverty and mental disorders among adolescents [23-29].

Adverse life events, poorer coping styles and weaker social support are examples of factors that are associated with disadvantaged socio economic class and account for some of the socioeconomic variation in depression [25- 29].

Limitation

A cohort where the students are followed up for a long time would have been worth-while.

Conclusion

All the spectrum of anxiety disorders was present among adolescents in their institution with varying degrees of associated factors.

Declarations

Ethical approval and consent to participate

Ethical clearance was specifically approved and granted by the Ethics Committee of University of Nigeria Teaching Hospital.

Availability of data and materials

The data will not be shared in order to protect the participants' anonymity

Authors’ contribution

All authors contributed to the conception and writing of the manuscript. AEC analyzed the manuscript.

Acknowledgements

We acknowledge the teachers in the schools who helped immensely in data collection. Their cooperation was unparalleled. There is no grant or any one that funded this work

References

1. Craske MG. Origins of phobias and anxiety disorders: why more women than men? Amsterdam: Elsevier; 2003.
2. Starcevic V, Castle DJ. Anxiety Disorders: in Stress: Concepts, Cognition, Emotion, and Behavior, 2016.
3. Kessler RC, Berglund P, Demler O, et al. Lifetime prevalence and age-of onset distributions of DSM-IV disorders in the National Comorbidity Survey Replication. Arch Gen Psychiatry 2005; 62: 593-602.
4. Bhandari KP, Adhikari C. Prevalence and factors associated with anxiety disorder among secondary school adolescents of Dang district, Nepal. Journal of Gandaki Medical College 2015; 8: 60-63.
5. Becker ES, Rinck M, Türke V, et al. Epidemiology of specific phobia subtypes: findings from the Dresden mental health study. Eur Psychiatry 2007; 22: 69-74.
6. Baxter AJ, Scott KM, Vos T, et al. Global prevalence of anxiety disorders: A systematic review and meta-regression. Psychol Med 2012; 43: 897-910.
7. Beesdo K, Knappe S, Psych D, et al. Anxiety and anxiety disorders in children and adolescents: Developmental issues and implications for DSM-V. Psychiatr Clin North Am 2009; 32: 483-524.
8. https://www.nigerianbulletin.com/threads/8-common-mental-disorders-affecting-nigerians.114256/
9. Reynolds CR, Richmond BO. What I think and feel: a revised measure of children's manifest anxiety. J Abnorm Child Psychol 1978; 6: 271-280.
10. Jalali M, Pourahmadi E. Prevalence of anxiety disorders among 10-14 years old children in Gorgan. European Psychiatry 2012: 27; 1.
11. Cartwright-Hatton S, McNicol K, Doubleday E. Anxiety in a neglected population: prevalence of anxiety disorders in pre-adolescent children. Clinical psychology review 2006; 26: 817-833.
12. Amirfakhraei A, Alinaghizadeh A. Epidemiology of mental disorders among adolescents in the city of Bandar Abbas, Iran, in 2012. Life Sci J 2012; 9: 976-980.
13. Ranjbar F, Nabdel Y, Fakhari A, et al. prevalence of psychiatric disorders among children and adolescents in north west of Tabriz. Medical Journal of Tabriz University of Medical Science & Health Service 2003; 25: 56-60.
14. Cartwright-Hatton S, McNicol K, Doubleday E. Anxiety in a neglected population: Prevalence of anxiety disorders in pre-adolescent children. Clin Psychol Rev 2006; 26:817-833.
15. 15.Horwath E, Lish JD, Johnson J, et al. Agoraphobia without panic: clinical reappraisal of an epidemiologic finding. Psychiatr Clin North Am 2009 Sep; 32: 483–524.
16. Beesdo K, Knappe S, Daniel SP. Anxiety and anxiety disorders in children and adolescents: Developmental issues and implications for DSM-V. Am J Psychiatry 1993; 150:1496-501.
17. Chaplin T, Gillham J, Seligman M. Gender, anxiety, and depressive symptoms. J Early Adolesc 2009; 29: 307-327.
18. Schmidt NB, Eggleston AM, Woolaway-Bickel K, et al. Anxiety Sensitivity Amelioration Training (ASAT): A longitudinal primary prevention program targeting cognitive vulnerability. Journal of Anxiety Disorders 2007; 21: 302-319.
19. Zvolensky MJ, Schmidt NB, Bernstein A, et al. Risk-factor research and prevention programs for anxiety disorders: a translational research framework. Behaviour Research and Therapy 2006; 44: 1219-1239.
20. Somers JM, Goldner EM, Waraich P, et al. Prevalence and incidence studies of anxiety disorders: a systematic review of the literature. Canadian Journal of psychiatry Review 2006; 51: 100–113.
21. Beesdo K, Knappe S, Pine DS. Anxiety and anxiety disorders in children and adolescents: Developmental issues and implications for DSM-V. Psychiatr Clin North Am 2009; 32: 483-524.
22. Pine DS, Cohen P, Gurley D, et al. The risk for early-adulthood anxiety and depressive disorders in adolescents with anxiety and depressive disorders. Arch Gen Psychiatry 1998; 55: 56-64.
23. Wittchen HU, Nelson CB, Lachner G. Prevalence of mental disorders and psychosocial impairments in adolescents and young adults. Psychol Med 1998; 28: 109-126.
24. Katie AM, Jane EC, William L, et al. Socioeconomic status and adolescent mental disorders. Am J Public Health 2012; 102: 1742-1750.
25. Costello EJ, Farmer EM, Angold A, et al. Psychiatric disorders among American Indian and white youth in Appalachia: the Great Smoky Mountains Study. Am J Public Health 1997; 87: 827-832
26. Costello EJ, Keeler GP, Angold A. Poverty, race/ethnicity and psychiatric disorder: A study of rural children. Am J Public Health 2001; 91: 1494-1498
27. Deater-Deckard K, Dodge KA, Bates JE, et al. Multiple risk factors in the development of externalizing behavior problems: group and individual differences. Dev Psychopathol 1998; 10: 469-493.
28. Turner RJ, Lloyd DA. The stress process and the social distribution of depression. J Health Soc Behav 1999; 40: 374-404.
29. Turner RJ, Wheaton B, Lloyd DA. The epidemiology of social stress. Am Sociol Rev 1995; 60: 104–125.