Introduction
|
A |
ttention deficit hyperactivity disorder (ADHD) is one of the most common childhood-onset psychiatric disorders1 that affects 2 – 14% of school-age children.1 – 14 Boys are more commonly affected by ADHD than girls and the male:female ratio is approximately 3:1 to 4:1.1, 15 Based on DSM-IV TR criteria, it has been estimated that one-third of children referred to psychiatric clinics are diagnosed as having ADHD. Conservative estimates evaluate the prevalence of ADHD to be 2% to 6% in the United States, with some studies reporting a prevalence of up to 17%. By the year 1987, a total of 6% of all public elementary school children in the United States were receiving stimulant medications.16 The prevalence of hyperkinetic disorder in United Kingdom is lower than United States and is approximately 2%.16
Although the onset of ADHD is usually prior to the age of seven years, there is a paucity of data on the prevalence of disorder in preschool children.17– 20 According to previous studies, the prevalence of this condition in preschool-age children is between 2% and 18.2%.20 – 23 Recent reports highlight behavioral, social, familial, and academic difficulties in preschool-age children with ADHD as compared to their counterparts without ADHD.24 Likewise, others have reported working memory deficits, mother-child disruption, and comorbid disruptive disorders in preschool-age children with ADHD.25 – 27
Evaluation of the prevalence of ADHD in preschool-age children can help clinicians to consider the diagnosis of ADHD and related psychiatric disorders in these children. Early intervention minimizes negative impact of the disorder and chronic failure and demoralization. On the other hand, delay in the diagnosis and treatment of ADHD in preschool children may result in developmental problems, comorbid psychopathology, disturbances in family functioning, and other psychiatric problems such as substance abuse.28 – 32
The purpose of this study was to determine the prevalence of ADHD in the general preschool population in Mashhad — the second largest city of the country located in North-East of Iran.
Patients and Methods
Thirty-four daycare kindergartens were selected at random from ten districts of Mashhad. One thousand and eighty-three (553 males and 530 females) children aged between five and six years were selected at random from 4,143 children of the selected kindergartens. Teachers and parents of these children were asked to complete a ten-item Conner’s Index questionnaire for each of these children. Score 15 was assumed as the cut-off point and those with scores >15 were considered positive.
Parents of children with positive screening tests were invited to participate in the next step during which parents and their children were interviewed directly in a semi-structured interview according to the Schedule for Affective Disorders and Schizophrenia for School-Age Children, Present and Lifetime Version (K-SADS-PL) ADHD section.33 The diagnosis for ADHD was also made by a direct interview based on DSM-IV diagnostic criteria. A psychiatrist or a highly-trained interviewer with extensive experience conducted all interviews. Data were analyzed by SPSS 11. To compare the prevalence of ADHD in boys and girls, χ2 test was used. Statistical significance criteria was set at P < 0.05.
Results
We found 133 children with ADHD, which translates to a prevalence rate of 12.3% (CI95%: 10.3 – 14.2%) in general population of preschool-age children. The prevalence was 18.1% (n = 96) in boys and 6.7% (n = 37) in girls (P < 0.0001) (Table 1).
Figure 1 shows the distribution of probands with ADHD in different districts of Mashhad.
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Table 1. Prevalence rate of ADHD by gender. |
|||||
|
|
ADHD |
Non-ADHD |
P value |
||
|
n |
% |
n |
% |
||
|
Male |
96 |
18.1 |
434 |
81.9 |
<0.001 |
|
Female |
37 |
6.2 |
516 |
93.3 |
|
|
|
|
Figure 1.Distribution of ADHD in probands of the children with ADHD in different districts of Mashhad. |
Discussion
This study examined the prevalence of ADHD in a community sample of 1,083 preschool-age children in Mashhad, North-East of Iran. Although a prevalence of 12.3% is consistent with some previous studies on community samples of preschool-age children in some countries, it is different with others.22, 24, 34
According to the studies, the prevalence of ADHD preschool children varies from 2% to 5% in the United States. 2, 20, 35 – 37
In India, it was found that the prevalence of ADHD increases with age; the prevalence at the age of three to four years was 5.2%.23 In Germany, researchers reported a prevalence of 9.6% at the age of five years.24 Shealy estimated a prevalence between 3% and 20%, depending on the age, the criteria and the instruments used for evaluation of ADHD.34 In Colombia, ADHD was found in 18.2% of preschool children.22
According to Kurtzke, epidemiological studies report in a higher prevalence, which should be considered as estimated or screening prevalence; many false positives may be included.38 That may explain parts of differences observed between the results obtained from different studies.
ADHD may be culture-dependent; what is considered abnormal in one culture may be acceptable in another. For instance, “to talk excessively;” intuitively, parents decide what “excessively” means according to their own culture.39, 40 So, the lower rates of ADHD may be attributed to under-recognition and delay of parents in seeking treatment for their preschool children or to the hesitance of some clinicians in diagnosing children in this age group.2
The prevalence of ADHD symptoms, and probably ADHD, was indeed high in our sample. There is no question that many more epidemiological studies on developmental disorders are required to advance our understanding of these disorders. Cross-national comparisons can be particularly useful for a comprehensive understanding of different developmental disorders.
Despite the lower rates of impairment in academic achievement, ADHD in preschool age is a severe disorder associated with impairment in multiple domains of functioning. Patients may have high rates of psychiatric comorbidity, morbidity, and impairment.2 Thus, there is no reason to assume that treatment of preschool-age children with ADHD should be any less aggressive than school-age children.26, 41, 42 Since little is known about the age specific response to treatment, clinicians should consider all options until further research results are available. Our results also propose the need for national schedules for screening, early diagnosis, and treatment of ADHD in preschool-age children before standing in elementary school.
Our results must be interpreted in the context of their methodological limitations. In this study, we had interview with only one parent — usually the mother — and relied on maternal reports, which might have led to a bias. Moreover, a temperamental constellation consisting of high activity level and short attention span, though in the normal range of expectation for a child’s age, should be considered. Differentiating these temperamental characteristics from cardinal symptoms of ADHD in preschool-age children is difficult mainly because of the overlapping features of a normally-immature nervous system. So, some of these children probably won’t later fulfill all of the criteria for ADHD. Despite these limitations, our results showed that the prevalence of ADHD in preschool-age children is as high as in the school age and clinicians should consider it to preventing the morbidity of the disorder earlier.
References
1 Swanson JM, Sergeant JA, Taylor E, Sonuga-Barke EJ, Jensen PS, Cantwell DP. Attention-deficit hyperactivity disorder and hyperkinetic disorder. Lancet. 1998; 351: 429 – 433.
2 Anderson JC, Williams S, McGee R, Silva PA. DSM-III disorders in preadolescent children. Prevalence in a large sample from the general population. Arch Gen Psychiatry. 1987; 44: 69 – 76.
3 Costello EJ, Angold A, Burns BJ, Stangl DK, Tweed DL, Erkanli A, et al. The Great Smoky Mountains Study of Youth. Goals, design, methods, and the prevalence of DSM-III-R disorders. Arch Gen Psychiatry. 1996; 53: 1129 – 1136.
4 Fergusson DM, Horwood LJ, Lynskey MT. Prevalence and comorbidity of DSM-III-R diagnoses in a birth cohort of 15 year olds. J Am Acad Child Adolesc Psychiatry. 1993; 32: 1127 – 1134.
5 Holborow PL, Berry P, Elkins J. Prevalence of hyper- kinesis: a comparison of three rating scales. J Learn Disabil. 1984; 17: 411 – 417.
6 Jensen PS, Watanabe HK, Richters JE, Cortes R, Roper M, Liu S. Prevalence of mental disorder in military children and adolescents: findings from a two-stage community survey. J Am Acad Child Adolesc Psychiatry. 1995; 34: 1514 – 1524.
7 McGee R, Feehan M, Williams S, Partridge F, Silva PA, Kelly J. DSM-III disorders in a large sample of adolescents. J Am Acad Child Adolesc Psychiatry. 1990; 29: 611 – 619.
8 Pelham WE Jr, Gnagy EM, Greenslade KE, Milich R. Teacher ratings of DSM-III-R symptoms for the disruptive behavior disorders. J Am Acad Child Adolesc Psychiatry. 1992; 31: 210 – 218.
9 Shekim WO, Kashani J, Beck N, Cantwell DP, Martin J, Rosenberg J, et al. The prevalence of attention deficit disorders in a rural midwestern community sample of nine-year-old children. J Am Acad Child Adolesc Psychiatry. 1985; 24: 765 – 770.
10 Szatmari P, Offord DR, Boyle MH. Ontario Child Health Study: prevalence of attention deficit disorder with hyperactivity. J Child Psychol Psychiatry. 1989; 30: 219 – 230.
11 Wolraich ML, Hannah JN, Pinnock TY, Baumgaertel A, Brown J. Comparison of diagnostic criteria for attention-deficit hyperactivity disorder in a county-wide sample. J Am Acad Child Adolesc Psychiatry. 1996; 35: 319 – 324.
12 Pineda DA, Lopera F, Palacio JD, Ramirez D, Henao GC. Prevalence estimations of attention-deficit/ hyperactivity disorder: differential diagnoses and comorbidities in a Colombian sample. Int J Neurosci. 2003; 113: 49 – 71.
13 Benjasuwantep B, Ruangdaraganon N, Visudhiphan P. Prevalence and clinical characteristics of attention deficit hyperactivity disorder among primary school students in Bangkok. J Med Assoc Thai. 2002; 85 (suppl 4): S1232 – S1240.
14 Montiel-Nava C, Pena JA, Montiel-Barbero I. Epidemiological data about attention deficit hyperactivity disorder in a sample of Marabino children [in Spanish]. Rev Neurol. 2003; 37: 815 – 819.
15 Cantwell DP. Attention deficit disorder: a review of the past 10 years. J Am Acad Child Adolesc Psychiatry. 1996; 35: 978 – 987.
16 Shaywitz SE, Shaywitz BA. Increased medication use in attention-deficit hyperactivity disorder: regressive or appropriate? JAMA. 1988; 260: 2270 – 2272.
17
American Psychiatric
Association. Diagnostic and Statistical Manual of Mental Disorders. 4th
ed (DSM-IV). Washington, DC: American Psychiatric
Association; 1994.
18 Biederman J, Faraone SV, Knee D, Munir K. Retrospective assessment of DSM-III attention deficit disorder in nonreferred individuals. J Clin Psychiatry. 1990; 51: 102 – 106.
19
Lahey BB, Pelham
WE, Stein MA, Loney J, Trapani C, Nugent K, et al. Validity of DSM-IV
attention-deficit/hyperactivity disorder for younger children.
J Am Acad Child Adolesc Psychiatry. 1998; 37:
695 – 702.
20 Wilens TE, Biederman J, Brown S, Tanguay S, Monuteaux MC, Blake C, et al. Psychiatric comorbidity and functioning in clinically referred preschool children and school-age youths with ADHD. J Am Acad Child Adolesc Psychiatry. 2002; 41: 262 – 268.
21 DuPaul GJ, McGoey KE, Eckert TL, van Brakle J. Preschool children with attention-deficit/hyperactivity disorder: impairments in behavioral, social, and school functioning. J Am Acad Child Adolesc Psychiatry; 2001; 40: 508 – 515.
22 Pineda D, Ardila A, Rosselli M, Arias BE, Henao GC, Gomez LF, et al. Prevalence of attention-deficit/hyperactivity disorder symptoms in 4- to 17-year-old children in the general population. J Abnorm Child Psychol. 1999; 27: 455 – 462.
23 Bhatia MS, Nigam VR, Bohra N, Malik SC. Attention deficit disorder with hyperactivity among pediatric outpatients. J Child Psychol Psychiatry. 1991; 32: 297 – 306.
24 Baumgaertel A, Wolraich ML, Dietrich M. Comparison of diagnostic criteria for attention deficit disorders in a German elementary school sample. J Am Acad Child Adolesc Psychiatry. 1995; 34: 629 – 638.
25 Mariani MA, Barkley RA. Neuropsychological and academic functioning in preschool boys with attention deficit hyperactivity disorders. Dev Neuropsychol. 1997; 13: 111 – 129.
26 Barkley RA. The effects of methylphenidate on the interactions of preschool ADHD children with their mothers. J Am Acad Child Adolesc Psychiatry. 1988; 27: 336 – 341.
27 Keenan K, Wakschlag LS. More than the terrible twos: the nature and severity of behavior problems in clinic-referred preschool children. J Abnorm Child Psychol. 2000; 28: 33 – 46.
28 Brook JS, Tseng LJ, Cohen P. Toddler adjustment: impact of parents’ drug use, personality, and parent-child relations. J Genet Psychol. 1996; 157: 281 – 295.
29 Campbell SB. Behavior problems in preschool children: a review of recent research. J Child Psychol Psychiatry. 1995; 36: 113 – 149.
30 Tarter RE, Laird SB, Kabene M, Bukstein O, Kaminer Y. Drug abuse severity in adolescents is associated with magnitude of deviation in temperament traits. Br J Addict. 1990; 85: 1501 – 1504.
31 Post RM. Transduction of psychosocial stress into the neurobiology of recurrent affective disorder. Am J Psychiatry. 1992; 149: 999 – 1010.
32 Barkley RA, Karlsson J, Pollard S, Murphy JV. Developmental changes in the mother-child interactions of hyperactive boys: effects of two dose levels of Ritalin. J Child Psychol Psychiatry.1985; 26: 705 – 715.
33 Kaufman J, Birmaher B, Brent D, Rao U, Flynn C, Moreci P, et al. Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version (K-SADS-PL): initial reliability and validity data. J Am Acad Child Adolesc Psychiatry. 1997; 36: 980 – 988.
34 Shealy AH. Attention-deficit hyperactivity disorder--etiology, diagnosis, and management. J Child Adolesc Psychiatr Nurs. 1994; 7: 24 – 36.
35 Bauermeister JJ, Canino G, Bird H. Epidemiology of disruptive behavior disorders. In: Greenhill L, ed. Child and Adolescent Psychiatric Clinics of North America. Philadelphia: Saunders; 1994: 177 – 194.
36 Hooks MY, Mayes LC, Volkmar FR. Psychiatric disorders among preschool children. J Am Acad Child Adolesc Psychiatry. 1988; 27: 623 – 627.
37 Lavigne JV, Gibbons RD, Christoffel KK, Arend R, Rosenbaum D, Binns H. Prevalence rates and correlates of psychiatric disorders among preschool children. J Am Acad Child Adolesc Psychiatry. 1996; 35: 204 – 214.
38 Kurtzke JF. Neuroepidemiology. In: Joint RJ, ed. Clinical Neurology. Vol. 4. Philadelphia: Lippincott; 1992: 1 – 29.
39 Reid R. Assessment of ADHD with culturally different groups: the use of behavioral rating scales. School Psychol Rev. 1995; 24: 537 – 560.
40 Reid R, DuPaul GJ, Power TJ, Anastopoulos AD, Rogers-Adkinson D, Noll MB, et al. Assessing culturally different students for attention deficit hyperactivity disorder using behavior rating scales. J Abnorm Child Psychol. 1998; 26: 187 – 198.
41 Greenhill LL. The use of psychotropic medication in preschoolers: indications, safety, and efficacy. Can J Psychiatry. 1998; 43: 576 – 581.
42
Sonuga-Barke EJ,
Daley D, Thompson M, Laver-Bradbury C, Weeks A. Parent-based therapies for
preschool attention-deficit/hyperactivity disorder: a
randomized, controlled trial with a community sample.
J Am Acad Child Adolesc Psychiatry. 2001; 40:
402 – 408.
43 Sadock BJ, Sadock I. Kaplan and Sadock's Synopsis of Psychiatry: Behavioral Sciences. 9th ed. Philadelphia: Lippincott Williams and Wilkins; 2003: 1223 – 1231.
