CC BY 4.0 · Journal of Child Science 2020; 10(01): e97-e103
DOI: 10.1055/s-0040-1716715
Original Article

A Cross-Sectional Study of 0.6 Million Children with Attention-Deficit/Hyperactivity Disorder in the United States

1  School of Production Engineering and Management, Technical University of Crete, Chania, Greece
› Author Affiliations
 

Abstract

Attention-deficit hyperactivity disorder (ADHD) is an increasingly recognized chronic neurodevelopmental disorder. This work aims at studying the prevalence and clinical characteristics of children with ADHD in the United States in the period between 2009 and 2018. Data from the National Health Interview Survey were analyzed by univariate and multivariate statistics to assess the role of socioeconomic factors in the development of ADHD. It has been studied 615,608 children, 51.2% male and 48.7% female. The prevalence of ADHD was 9.13%, with males predominating over females. The number of children with ADHD increased from 2009 to 2018 by 14.8%. As specified by multiple logistic regression analysis, males (odds ratio [OR] 2.38) who have neither mother nor father (OR 1.76) are twice as likely to have ADHD compared with their peers. In addition, family income (OR 1.40) and parent's education (OR 1.12) were significantly associated with ADHD. It has been highlighted the significance of deprivation of both family and financial comfort as primary indicators for ADHD in children. Moreover, children with ADHD were more likely to be males in the age group of 12 to 17.


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Introduction

Attention-deficit hyperactivity disorder (ADHD) is a chronic neurodevelopmental disorder in which children cannot handle their behavior due to difficulty in processing neural stimuli, followed by high activity levels.[1] Inattention, impulsivity, and hyperactivity are some of the symptoms that the child is faced with.[2] [3] [4] The prevalence of ADHD ranges from 1 to 20% among children and adolescents worldwide.[5] [6] [7] [8] [9] The knowledge of the prevalence of ADHD among children is of paramount importance for further response scheduling, resource allocation, training, and research.[10]

Low socioeconomic status (SES) has been linked not only to poor physical health but also to impaired mental health in childhood.[11] [12] [13] [14] [15] [16] [17] [18] [19] In particular, children from low socioeconomic backgrounds are 1.18 to 3.34 times more likely to have mental health problems than their peers.[19] The association between ADHD and SES appears to be complex because symptoms are associated with interactions between genes and the environment during development.[20] Other proposed factors that could be involved include maternal mental health,[21] substance abuse,[22] as well as the parent's involvement in the upbringing of their child.[23]

It is of utmost importance to acknowledge the seriousness of ADHD in children, and the knowledge of underlying factors that lead children to ADHD. For this purpose, this work studied ADHD in the United States during the period 2009 to 2018 with the aim to find statistically significant socioeconomic indicators for this type of disorder.


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Methods

The data used in this work originate from the National Health Interview Survey (NHIS) data set[24] and cover the period 2009 to 2018. The target population for NHIS is the civilian noninstitutionalized population of the United States. NHIS data are collected through personal household interviews. The main objective of NHIS is to monitor the health of the U.S. population through the collection and analysis of data on a broad range of health topics. Each year, a representative sample of households across the country is selected for NHIS using a multistage cluster sample design. Trained interviewers from the U.S. Census Bureau visit each selected household and administer the NHIS in person. To identify children with ADHD, each household was asked to answer the question: “Has a doctor or other health professional ever told you that [child's name] had ADHD or attention deficit disorder?” Statistical methods were chi-square test for categorical variables and one-way analysis of variance for continues variables to check the hypothesis that the prevalence of ADHD was not associated with socioeconomic characteristics (gender, age, race, origin, parent's education, family income, poverty status, health insurance coverage, current health status, family structure, place of residence, and region). Factors associated with ADHD were identified by multiple logistic regression analysis. Children with ADHD (case group) were compared with a matched cohort of children without this condition (control group). Factors associated with ADHD were represented using the odds ratio (OR) and 95% confidence intervals, and a p-value of < 0.05 was considered statistically significant. Particularly, the OR has been used to compare the relative odds of occurrence of the outcome of interest (children with ADHD), given exposure to the variable of interest (specific socioeconomic characteristics of children).[25] The study was performed using IBM SPSS 25 software package for Windows.

All procedures performed were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.


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Results

Participants of this study were 615,608, 51.2% males and 48.7% females. Moreover, 13.5% of the participants were 0 to 4 years old, 46.5% of them were 5 to 11 years old, and finally, 40.1% of them were 12 to 17 years old. The number of children and adolescents with ADHD was 56,252. As shown in [Table 1], ADHD was more frequent in males, in the age group of 12 to 17 years, and in Caucasians. Most children with ADHD had parents with high education—more than a high school diploma (69.2%)—and excellent or very good health status (72.1%). Moreover, most families whose children have ADHD were not poor (51.4%), with a family income of $35,000 or more (38.4%) and private health insurance coverage (47.5%). Finally, most children with ADHD had both mother and father as family structure (57.5%) and live in southern U.S. (43.1%), in large metropolitan areas with a population size of one million or more (47.3%).

Table 1

Chi-square and one-way ANOVA test

Characteristics of children with ADHD: United States 2009–2018

Children with ADHD

Percentages

p-Value

Gender

< 0.05

Male

39,308

69.9%

Female

16,944

30.1%

Age

< 0.05

3–4

1,228

2.2%

5–11

24,280

43.2%

12–17

30,746

54.7%

Race

< 0.05

White

42,627

81.4%

Black or African American

9,104

17.4%

Asian

627

1.2%

Origin

< 0.05

Hispanic or Latino

8,491

8.1%

Mexican or Mexican American

4,930

4.7%

Not Hispanic or Latino

47,762

45.4%

White. single race

35,315

33.6%

Black or African American. single race

8,598

8.2%

Parent's education

< 0.05

Less than a high school diploma

5,333

10.1%

High school diploma

10,972

20.7%

More than a high school diploma

36,603

69.2%

Family income

< 0.05

Less than $35,000

19,888

23.1%

$35,000 or more

33,065

38.4%

$35,000–$49,999

6,438

7.5%

$50,000–$74,999

8,078

9.4%

$75,000–$99,999

5,411

6.3%

$100,000 or more

13,137

15.3%

Poverty status

< 0.05

Poor

13,522

25.1%

Near poor

12,677

23.5%

Not poor

27,666

51.4%

Health insurance coverage

< 0.05

Private

26,593

47.5%

Medicaid

25,535

45.6%

Other coverage

1,671

3.0%

Uninsured

2,238

4.0%

Current health status

< 0.05

Excellent or very good

40,552

72.1%

Good

12,670

22.5%

Fair or poor

3,034

5.4%

Family structure

< 0.05

Mother and father

32,334

57.5%

Mother, no father

18,239

32.4%

Father, no mother

2,418

4.3%

Neither mother nor father

3,262

5.8%

Place of residence

< 0.05

MSA (metropolitan statistical area)

Large MSA (population size 1 million or more)

26,611

47.3%

Small MSA (less than 1 million)

19,578

34.8%

Not in MSA

10,064

17.9%

Region

< 0.05

Northeast

9,023

16.0%

Midwest

14,123

25.1%

South

24,242

43.1%

West

8,869

15.8%

Abbreviations: ADHD, attention-deficit hyperactivity disorder; ANOVA, analysis of variance.


Most children in the control group were females, in the age group of 5 to 11, and Caucasians. Most children of the control group had parents with high education—more than a high school diploma (69.5%)—and excellent or very good health status (84.5%). Moreover, most families from the control group were not poor (57.8%), with a family income of $35,000 or more (41.4%) and private health insurance coverage (55.9%). Finally, most children from the control group had both mother and father as family structure (69.5%) and they live south (36.4%), in a large metropolitan statistical area with a population size of one million or more (58.0%).

[Table 2] represents the multiple logistic regression analysis with the ORs with the aim of finding predictors for ADHD. As can be seen in [Table 2], all prognostic factors were statistically significant (p < 0.05). Based on multiple logistic regressions, children who were more likely to have ADHD were black or African Americans (OR 5.4), males (OR 2.38), and in the age group of 12 to 17 (OR 1.0), with parents having “high school diploma” as education status (OR 1.12). Moreover, children whose parents had a family income less than $35,000 (OR 1.4) and Medicaid health insurance coverage (OR 2.2) were twofold more likely to have ADHD. In addition, poor children (OR 1.62), with “fair or poor” current health status (OR 1.00), who live south (OR 1.86), “not in a metropolitan statistical area” (OR 1.00), were more likely to have ADHD. Finally, children who had neither mother nor father were also more likely to have ADHD (OR 1.76).

Table 2

Statistically significant predictors of ADHD in children using multivariate logistic regression

Socioeconomic characteristics of children: United States 2009–2018

Patients

Controls

Odds ratio (95%CI)

p-Value

Gender

< 0.05

Male

39,308

276,048

2.38 (2.33–2.42)

Female

16,944

283,308

1.0 (ref)

Age

< 0.05

3–4

1,228

82,016

0.10 (0.10–0.11)

5–11

24,280

262,956

0.65 (0.64–0.66)

12–17

30,746

216,951

1.0 (ref)

Race

< 0.05

White

42,627

416,541

4.98 (4.6–5.4)

Black or African American

9,104

82,076

5.4 (4.98–5.86)

Asian

627

30,557

1.0 (ref)

Origin

< 0.05

Hispanic or Latino

8,491

138,513

0.54 (0.52–0.56)

Mexican or Mexican American

4,930

94,190

0.46 (0.44–0.48)

Not Hispanic or Latino

47,762

423,414

1.0 (0.97–1.0)

White single race

35,315

293,397

1.01 (1.04–1.09)

Black or African American, single race

8,598

76,337

1.0 (ref)

Parent's education

< 0.05

Less than a high school diploma

5,333

65,515

0.83 (0.81–0.86)

High school diploma

10,972

100,341

1.12(1.10–1.15)

More than a high school diploma

36,603

377,321

1.0 (ref)

Family income

< 0.05

Less than $35,000

19,888

152,705

1.4 (1.4–1.5)

$35,000 or more

33,065

365,674

1.02 (1.00–1.04)

$35,000–$49,999

6,438

63,897

1.14 (1.10–1.17)

$50,000–$74,999

8,078

87,394

1.04 (1.01–1.07)

$75,000–$99,999

5,411

65,711

0.93 (0.90–0.96)

$100,000 or more

13,137

148,677

1.0 (ref)

Poverty status

< 0.05

Poor

13,522

103,020

1.45 (1.42–1.48)

Near poor

12,677

120,095

1.16 (1.14–1.19)

Not poor

27,666

305,974

1.0 (ref)

Health insurance coverage

< 0.05

Private

26,593

313,087

1.4 (1.3–1.4)

Medicaid

25,535

194,357

2.2 (2.1–2.3)

Other coverage

1,671

14,770

1.89 (1.77–2.0)

Uninsured

2,238

37,480

1.0 (ref)

Current health status

< 0.05

Excellent or very good

40,552

474,701

0.26 (0.25–0.27)

Good

12,670

77,857

0.49 (0.47–0.52)

Fair or poor

3,034

9,266

1.0 (ref)

Family structure

< 0.05

Neither mother nor father

3,262

17,000

1.76 (1.66–1.86)

Mother, no father

18,239

132,207

0.76 (0.72–0.79)

Father, no mother

2,418

22,208

1.26 (1.21–1.32)

Mother and father

32,334

390,514

1.0 (ref)

Place of residence

< 0.05

MSA (metropolitan statistical area)

Large MSA (population size 1 million or more)

26,611

311,997

0.6 (0.58–0.61)

Small MSA (less than 1 million)

19,578

155,337

0.9 (0.86–0.91)

Not in MSA

10,064

70,927

1.0 (ref)

Region

< 0.05

Northeast

9,023

91,913

1.54 (1.5–1.6)

Midwest

14,123

125,650

1.77 (1.72–1.82)

South

24,242

204,506

1.86 (1.82–1.91)

West

8,869

139,856

1.0 (ref)

Abbreviations: ADHD, attention-deficit hyperactivity disorder; CI, confidence interval.


[Fig. 1] represents the trend in ADHD in children during the years 2009 to 2018 in the United States. The number of children with ADHD increased from 2009 to 2018 by 14.8%. Moreover, the prevalence of ADHD in this decade was 9.13%. [Fig. 2] represents the prognostic factors with the ORs for ADHD. As can be seen, ethnicity ranks first, followed by gender, health insurance coverage, region, and family structure.

Zoom Image
Fig. 1 Trend in attention-deficit hyperactivity disorder (ADHD) during the years 2009 to 2018 in the United States.
Zoom Image
Fig. 2 Prognostic factors with the odds ratios for attention-deficit hyperactivity disorder (ADHD).

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Discussion

The number of children diagnosed with ADHD in the United States during the years 2009 to 2018 increased at an alarming rate of 14.8%. Children who had neither mother nor father were twice as likely to have ADHD. This can be explained by the fact that the lack of parents reflects problems in the psychopathology of the child. These results are in agreement with prior studies, in which ADHD was linked to the lack of parent's involvement in the upbringing of their child.[26]

Additionally, family income and poverty status play a key role in the occurrence of this type of disorder. Children living in a poor financial situation and low SES were more likely to have ADHD. The results of this study are in agreement with prior studies, in which it has been reported that although ADHD is highly heritable, symptoms are associated with interactions between genes and the environment during development such as low SES and chaos (household disorganization).[27] It has also been found that socioeconomic disadvantage was associated with emotional and conduct problems in children but neither home environment nor parenting attenuated this association, indicating the decisive role of SES in the child's psychopathology.[28]

The importance of this study lies in the interaction between multiple socioeconomic variables and ADHD, which reflects the complexity and multidimensional nature of deprivation, as well as the various roles of these dimensions during the course of life, which in turn reflects the longest gestation period for ADHD. Deprivation has been linked to stress, which in turn influences human behavior and health. More specifically, stressors in early life are responsible for the production of cortisol, a hormone that peaks in response to stressful experiences, and has not only immunological effects but also social and behavioral consequences.[29] [30]

One limitation of the present study is that data were collected through personal household interviews. Nondisclosure of a characteristic of the child by participants is possible due to memory and/or social bias. Another limitation of the study is that multiple logistic regression analysis does not establish causality between variables.


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Conclusion

The results of this work explain the significance of deprivation (of family and financial comfort) as the main prognostic factor for ADHD. Moreover, children with ADHD are more likely to be black or African American, males in the age group of 12 to 17.


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Conflict of Interest

None declared.


Address for correspondence

Irene Rethemiotaki, MSc
School of Production Engineering and Management, Technical University of Crete, Kounoupidiana
GR-73100 Chania
Greece   

Publication History

Received: 31 May 2020

Accepted: 07 August 2020

Publication Date:
14 September 2020 (online)

© .

Georg Thieme Verlag KG
Stuttgart · New York


  
Zoom Image
Fig. 1 Trend in attention-deficit hyperactivity disorder (ADHD) during the years 2009 to 2018 in the United States.
Zoom Image
Fig. 2 Prognostic factors with the odds ratios for attention-deficit hyperactivity disorder (ADHD).