Last modified at 1/4/2013 4:01 PM by Lareza Lazuardi

Introduction to ADHD

ADHD is a neurobiological disorder

Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurobiological disorder that interferes with an individual's capacity to do the following, in developmentally appropriate ways:

  • regulate activity level (hyperactivity)
  • inhibit behaviour (impulsivity)
  • attend to the task at hand (inattention)1

The term "Attention-Deficit/Hyperactivity Disorder" is usually abbreviated and referred to as "ADHD." The observable symptoms of ADHD include an inability to sustain attention and concentration, developmentally inappropriate levels of activity, distractibility, and impulsivity. Symptoms of ADHD may appear over the course of many months, often with the symptoms of impulsiveness and hyperactivity preceding those of inattention, which may not emerge for a year or more.

ADHD is generally first noticeable during the preschool years and is likely to persist into adolescence and adulthood. This chronic condition affects many areas of a child's functioning, most notably self-control of behaviour, school achievement, and the development of social skills and positive relationships.

Individuals with ADHD vary widely in their particular skills and difficulties. Also, ADHD rarely occurs by itself. That is, individuals with ADHD frequently have other types of co-existing mental health problems (such as oppositional defiant behaviour, aggression, or high levels of anxiety) and/or specific learning disabilities such as reading disability and language impairments.2 3 These co-existing problems (which are described in subsequent sections) may further increase the risk for poor educational and social outcomes. Individuals with ADHD can be very successful in life, but...

without identification and proper treatment, the neurobiological disorder known as "ADHD" may have serious consequences, including school failure, depression, problems with relationships, substance abuse, delinquency, risk for accidental injuries, and job failure.4 Thus, early identification, diagnosis, and treatment of ADHD are extremely important.

The most widely used medical system for diagnosing ADHD is known as the Diagnostic and Statistical Manual for Mental Disorders, Fourth Edition, or DSM-IV.5 The DSM-IV identifies two main clusters of ADHD symptoms: Inattention and Hyperactivity/Impulsivity. Some children display mainly symptoms of inattention and are not overly active or impulsive. They would meet the current diagnostic criteria for Predominantly Inattentive Subtype. Previously, this pattern of behavioural symptoms was referred to "ADD" (Attention Deficit Disorder, without Hyperactivity).

A few children show mainly hyperactive/impulsive behaviour. They would meet the diagnostic criteria for Predominantly Hyperactive/Impulsive Subtype.

Most school-aged children with ADHD show both types of behavioural symptoms and so meet the diagnostic criteria for Combined Subtype of ADHD.


Figure 1-1: Symptoms and Subtypes of ADHD

 

Prevalence of ADHD in children

ADHD is a very common problem. It has been found to affect between 5% and 12% of the school-aged population worldwide.6 7 ADHD is about three times more common in boys than in girls.

For educators, this prevalence rate translates into potentially one to two children in every classroom (depending on class size), in countries such as Canada, the United States, Japan, China, India, and Australia, as well as in European, South African, and South American countries.

ADHD also affects about one in 25 adults (that is, 4%), making it one of the most common mental health problems in adulthood as well as in childhood.8 From a school perspective, this means that it is highly likely that several professionals in any school system experience the burden of ADHD themselves —; evidence that ADHD does not preclude a successful outcome in adulthood.

However, it is also important to understand that although specialists refer to ADHD as a disorder, suggesting that a person may either have ADHD or not have ADHD, the symptoms occur on a continuum of risk (like blood pressure).

This means that there may be several students in a class who exhibit some problematic behavioural symptoms (for example, moderately inattentive), but do not meet the diagnostic criteria for ADHD. Nonetheless, these students may also experience adverse outcomes. In particular, it has been noted that children who exhibit moderate to severe levels of inattention, yet who may not receive a diagnosis of ADHD, are at risk for poor reading achievement, poor grades, and grade retention.4 9-11

It is for this reason that the teaching strategies in TeachADHD are designed to be "best practices" for all students, including those with subclinical levels of ADHD symptoms as well as those with a diagnosis of ADHD.

Taking a closer look at symptoms of ADHD

Symptoms of ADHD are always present to some degree, but they usually vary moment by moment, hour by hour, day by day, and from one situation to another. The symptoms of ADHD are often more noticeable in the following contexts: when there is little or no external support and control provided by an adult; when work is more complex, involving multiple steps and continuous effort; and when the work or activity must be completed rapidly or in a designated time frame. The emergence of more severe ADHD-like behaviour may signal a mismatch between the student's capacity for controlled attention, the demands of the task, and environmental support.

Tables 1-1 and 1-2 provide typical descriptions of the various symptoms of inattentive and hyperactive/impulsive behaviour. The left-hand column describes the symptom of ADHD and the right-hand column provides examples of how that symptom may manifest in the classroom.15


Table 1-1: Manifestation of ADHD Symptoms in the Classroom15

Inattentive symptoms specified by DSM-IV Child stands out from peers in behaviours like the following
Distracted very easily Constantly looking around, head on a swivel, watching what others are doing
Pulled away from task at hand by other events or noises going on in-class, in the hallway, outside the window
Difficulty concentrating on tasks for a reasonable length of time Starts on an assignment but then loses focus
May look day-dreamy or lost in thought and needs prompt to get back to work
Stares into space, at others, or at materials, but unfocused and does not get self back on task
Difficulty paying close attention to detail (often makes careless mistakes) Rarely includes required details, such as name and date
Rarely checks, edits, or proofreads own work before handing it in
Problems following instructions and completing activities May leave things half done, rush through work and not have followed instructions, or need constant supervision to continue and complete work
Difficulty keeping track of their personal belongings and materials Constantly looking for materials (such as pencils, books, or personal belongings)
Doesn't get started on work because he or she can't find needed materials: "Where's my..."
Struggles to remember routines and organize tasks, activities and things required for school (for example, writing assignments in homework book) Forgets to jot assignments down in agenda book and forgets to hand in homework
Has materials but they are disorganized
Has difficulty completing independent projects with multiple steps
Difficulty getting started on activities, particularly those that are challenging Engages in active avoidance (for example, does something else, wanders around)
May need active supervision or prompting to get started
Difficulty organizing work and leisure activities Coat-hooks, cubby-holes, locker, desk, and backpack in constant disarray; materials spilling out everywhere
Papers misfiled or simply pushed into bag or other container
Toys, sports equipment, and other leisure materials mixed with clothes and school work
Does not seem to be listening when spoken to directly Has difficulty keeping focused on the conversation
May be able to repeat none or only some of the instructions just given in direct face-to-face conversation


Table 1-2: Manifestation of ADHD Symptoms in the Classroom15

Hyperactive-impulsive symptoms specified by DSM-IV Child stands out from peers in behaviours like the following
Often fidgets, squirms, and turns around in the seat constantly during a lesson May frequently drum fingers or tap a pencil on desk, repeatedly shift body positions on chair, and swing legs back and forth
Seems like they are constantly on the go in the classroom Rocks chair, constantly stands up or leans over desk, sits on one leg then the other, twirls on the seat or carpet
Continually touches, grabs, or plays with objects in close reach
Makes a lot of noise even during play or leisure activities Loud singing or talking during play or quiet time activities
Loud conversations
Fails to modulate volume of voice in class or use an "indoor voice"
Bangs things on the desk
Talks incessantly when not supposed to talk (but doesn't say enough when called upon to respond to a question) Very chatty and talks to others when supposed to be getting ready or working
May also ramble on about something that is not focus of discussion
Blurts out answers before hearing the whole question Starts talking or responding before the teacher finishes his or her question or comment
May shout out comment or question before instructions are finished
Interrupts other's conversations or activities Talks over or cuts off the person who is talking
Interrupts peers' games or activities
Grabs toys or objects from others without permission
Becomes easily frustrated waiting in line or when asked to take turns Does not wait to be called upon during question/answer or discussion activities but rather calls out their answer or comment
Wants to be first in line
Gets upset, restless, or disruptive when waiting in line
Leaves seat in classroom or other situation in which student is expected to stay in seat Frequently stands instead of sitting at desk
Wanders around the classroom
Gets up during seat work to talk or go sharpen pencil
Moves from place to place on carpet during circle time (for younger students)
Runs about in the classroom or is climbing excessively when it is not appropriate Slides or runs down hallways
Runs from one activity to another when supposed to walk
Climbs over desks

Behavioural symptoms of ADHD vary in their manifestation

Each child with ADHD will exhibit a unique behavioural profile which in turn will be affected by a number of factors. It is important to remember that:

  • Different symptoms may appear in different settings, depending on the demands the situation may impose on the child's need for self-control.
  • Moreover, ADHD symptoms vary from moment to moment:
    • Symptoms increase when there is little or no external structure or control, little demand for active engagement, or high cognitive demand.
    • Symptoms decrease and performance improves when frequent and immediate rewards are given and when the activity itself is intrinsically motivating to the individual (for instance, self-selected activities such as videogames), as well as when there is high external structure and control.
  • Symptoms of inattention are much less noticeable than are symptoms of hyperactivity/impulsivity in the classroom, and so are more readily overlooked.
  • Symptoms of ADHD are less noticeable and less disruptive in girls (see next section).
  • Overt symptoms of hyperactivity/impulsivity decline with increasing age:
    • Adolescents and younger and older adults may experience impairing levels of inner restlessness even though the overt symptoms are less noticeable.

Different profiles of ADHD

Profiles vary by subtype of ADHD

There are three subtypes of ADHD, classified on the basis of the relative predominance of inattention and hyperactive/impulsive symptoms: Predominantly Inattentive subtype, Predominantly Hyperactive subtype, and the Combined subtype (in which children exhibit both inattentive and hyperactive-impulsive symptoms). The two most prevalent subtypes are the Combined and the Predominantly Inattentive subtypes.5

Research has shown that academic and school problems tend to be associated with the Combined and Inattentive subtypes, which share the behavioural dimension of inattention. Thus, students with ADHD Predominantly Inattentive or Combined subtypes are more likely to fail a grade and/or receive significantly lower grades than their non-ADHD peers. Specifically, Inattention symptoms are considered a "developmental risk factor" due to their link with academic underachievement in literacy and numeracy skills and poor school adjustment. In adolescence and adulthood, many individuals who met criteria for Combined subtype in childhood no longer manifest as many hyperactive-impulsive symptoms, with a resulting shift in diagnosis to Predominantly Inattentive subtype.

By contrast, students with the Predominantly Hyperactive/Impulsive subtype are less likely to exhibit problems with academic achievement. However, they are much more likely than the Inattentive subtype to exhibit oppositional, defiant, and aggressive behaviour. Often children receive this diagnosis when they are younger. These disruptive behaviour problems are also shown by students with the Combined Type, which is not surprising since these two subtypes exhibit similar hyperactive-impulsive symptomatology.

ADHD looks different in girls

More boys are diagnosed with ADHD than girls. This gender difference may be in part because the symptoms displayed by girls with ADHD are less noticeable in the classroom than those of boys.16 For example, research indicates that:

  • Girls with ADHD are less likely than boys with ADHD to exhibit observable behaviours in the classroom, including:
    • interference behaviours: clowning around, interrupting others, talking during work
    • gross motor behaviours: standing up, running, skipping
    • physically aggressive behaviours
  • However, girls with ADHD are more likely than boys with ADHD to exhibit:
    • verbal aggression (such as teasing, name-calling, and taunting) towards peers
  • Boys and girls with ADHD do not differ from each other in:
    • off-task behaviours
    • minor motor movements (such as rocking movements)
    • cognitive function and academic achievement

Despite these differences in the manifestation of the overt behavioural symptoms, girls with ADHD are as impaired as boys with ADHD in a number of domains, including academic and social skills. However, girls with ADHD are more likely than boys with ADHD to be overlooked and under-diagnosed.

ADHD and comorbidity

Table 1-3: Rates of Comorbid Conditions among Children with ADHD 2-3 17 18

Other concurrent mental health conditions Concurrent learning disabilities
Anxiety/mood disorders 38% Oral language disorders: receptive/expressive 8% to 30%
Severe tics/Tourette's disorder 11% Reading disorder (phonologically-based disorders) 15% to 40%
Oppositional defiant disorder 40% Mathematics disorder 10% to 25%
Conduct disorder 14% Written language expression Unclear (clinical study suggests about 65%)19

Comorbid conditions may alter the typical manifestation of ADHD in the classroom

In this section we focus on the comorbidity of ADHD with other mental health conditions (comorbidity with learning disabilities is discussed in Chapter 4).18 20-21 The profiles described below indicate how the comorbid condition might alter the classroom presentation of ADHD. But keep in mind that students with both ADHD and the various comorbid conditions also show difficulty concentrating, are easily distracted, have difficulty remembering and organizing their materials, fidget, and may act before thinking. Moreover, they may show even more problems with school work and social interaction than do students with only ADHD.

ADHD with comorbid anxiety or depression:22 Most children experience fears, worries, or sadness in childhood and adolescence that are transitory or specific to a stage of development; these are considered to reflect normal development. But when children's fears, worries, or sadness persist and are accompanied by impairments in social function, they may meet the diagnostic criteria for an anxiety disorder. Anxiety makes children feel hopeless. Students who have anxiety in the elementary school years are at risk for depression as teenagers during high school.

Students with ADHD and comorbid anxiety disorders are "worriers." In striking contrast to nonanxious children with ADHD, those with comorbid ADHD and anxiety disorders may worry about:

  • their competency and performance in academics, athletics, and social situations
  • their behaviour
  • their parents or other close family members
  • what other people, including teachers and peers, might think about what they say or do
  • future events, such as appointments with doctors or dentists, tests at school, school trips, and new activities, including new classroom activities

These students may not talk openly about their worries, but rather their anxiety is shown in different ways, including:

  • looking tense when sitting in desk
  • becoming flushed, getting sweaty palms and dry mouth (resulting in frequent lip licking or a "clicking sound" while speaking), talking with a quavering voice, speaking rapidly with many stops and restarts in a quiet voice or whisper, or even "going blank" when called upon to answer a question or in testing situations
  • nervous mannerisms (for example, nail biting, leg jiggling, breath holding, or gulping)
  • reluctance to leave parents and come to school, or to leave teacher and go out to the playground
  • constantly seeking reassurance from the teacher about their performance ("Is this what I'm supposed to do?" "Is this the right answer?" "Am I doing OK?" "Did other kids do better than me?")
  • refusing to comply with a teacher's requests and becoming oppositional in an attempt to avoid a new or challenging situation (a coping strategy, albeit a maladaptive and ineffective one)

Students with ADHD and comorbid depression "carry the world on their shoulders." These students may experience hopelessness, but rarely talk spontaneously about what is troubling them. In the classroom these children may reveal their sadness in the following ways:

  • hunched, stooped posture, head down with little eye contact, when walking around or sitting at desk
  • looking pale, listless, sad, tearful
  • rarely or never laughing like other children when something funny happens in class
  • not appearing to have fun or experience joy at school or on the playground
  • low self-esteem
  • poor school performance
  • a lot of unexplained absenteeism
  • may think about and may even make comments to teachers, parents, or peers about killing themselves

ADHD with Oppositional Defiant Disorder (ODD) or Conduct Disorder (CD): Most children, including those with ADHD, at times refuse to do what adults want them to do, may answer back, may tell "fibs" (little lies), get angry and stamp their feet, yell, or even hit the person with whom they disagree or are angry. These behaviours are considered to be part of normal development and the child or adolescent learns that this way of behaving is not socially acceptable. But when these difficult-to-manage behaviours occur frequently and persist, the student may also meet diagnostic criteria for ODD or CD.

Students with ADHD and comorbid ODD are "big reactors." In the classroom, their tendency to be negativistic and defiant may be shown in the following ways:

  • slamming books down on the desk or throwing things, stamping, yelling at others, having temper tantrums
  • talking back to the teacher and refusing to back down, refusing to comply ("You can't tell me what to do")
  • deliberately and persistently annoying others by poking, pulling, or grabbing
  • never accepting responsibility for own misbehaviour and blaming others
  • whining and complaining to the teacher about the teacher or about others ("It's not fair," "You never give me a chance," "He always does it to me")
  • holding grudges or trying to get back at others by being spiteful or vindictive

Students with ADHD and comorbid Conduct Disorder (CD) may be either "ticking bombs" or "cool law breakers." At school, conduct disorder may be evident in the following ways:

  • violent and uncontrollable physically aggressive behaviour ("rage attacks") directed towards people or school property
  • subtle but persistent verbal aggression, such as taunting, name-calling, or verbal threats (particularly by girls)
  • persistent pattern of truancy from school or leaving school property without permission
  • serious and blatant lying
  • carrying weapons such as knives
  • carrying matches and frequently playing with fire (perhaps even engaging in arson)
  • "joy-riding" by stealing and using bicycles, motorcycles, or cars
  • repeated contacts with police

Behaviour associated with Conduct Disorder is serious and requires the immediate support and help of professionals with expertise in this area.

ADHD look-alikes

Not everything that looks like ADHD is ADHD!

For example, children who are very worried about events at home (such as parental separation or divorce, or stressful events such as moving or the death of a close relative or pet) or about things in general (such as world events, performance in school, or what others might think) may also have difficulty concentrating, listening to and following instructions, and sitting still, and may be easily distracted and make careless errors. These students may have anxiety disorders or depression alone, and not ADHD.

Children with specific learning disabilities and/or language impairments may also show some behavioural symptoms of ADHD. Excessive tiredness, chronic hunger, medication for other health problems (for example, asthma), brain injury following an accident, Fetal Alcohol Spectrum Disorder, and severe developmental delay (mental retardation) might also result in behavioural problems that look like ADHD. This is why it is important that a physician is consulted about a diagnosis of ADHD in order to rule out other medical explanations of the ADHD symptoms.

Diagnosis of ADHD

All children are sometimes restless, sometimes act without thinking, sometimes can't concentrate, and sometimes may daydream the time away. However, when the child's hyperactivity, distractibility, impulsivity, or poor concentration begins to affect performance in school, social relationships with other children, or behaviour at home, ADHD may be suspected. But because the symptoms vary so much across settings and other problems may mimic ADHD, this neurobiological condition is not easy to diagnose. For example, a child who "can't sit still" or is otherwise disruptive is very noticeable in school, but the quiet and inattentive daydreamer may be overlooked. The impulsive child who acts before thinking may be considered just a "discipline problem," while the child who is passive or sluggish may be viewed as merely unmotivated. Yet all of these problems may signify ADHD.

In Canada and the United States, a clinical diagnosis of ADHD can be made by several types of professionals, including a clinical psychologist, psychiatrist, paediatrician, neurologist, or family physician. In other countries the diagnosis of ADHD may be made only by certain types of medical doctors (for example, paediatricians or child psychiatrists). However, the medical professions have developed clinical practice guidelines for the assessment and diagnosis of ADHD and related disorders.12-14 To make a diagnosis, information about the child's difficulties is gathered from several sources:

  • early developmental history
  • interviews with parents and child about current and past symptoms
  • behaviour rating scales and/or diagnostic interviews completed by parents, child, and teachers
  • review of school performance, achievement, and language skills

To determine whether a child has ADHD, the diagnostician considers whether the child's behavioural difficulties are excessive, long-term, and pervasive. That is, do they occur more often than in other children of the same age and gender? Are they a continuous problem, or just a response to a temporary situation? Do the behaviours occur in several settings, or only in one specific place like the playground or during individual seat-work in the classroom?

In Canada, the U.S.A., and many other countries, the child's pattern of behaviour is compared against a set of criteria and characteristics of the disorder as listed in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV):5

  • evidence of at least six of nine symptoms of inattention and/or at least six of nine symptoms of hyperactivity/impulsivity
  • symptoms are developmentally inappropriate for the child's age
  • symptoms are impairing to the child's functioning in at least two areas of the child's life, such as at home, in the classroom, in the community, or in social settings
  • symptoms must appear early in life, before age seven, and continue for at least six months

The teacher's role in the referral, assessment, and treatment of children with ADHD

Teachers are often the first to notice that students are experiencing difficulty in meeting the learning expectations of the classroom (for example, problems finishing assignments, organizing work, and staying on-task and/or exhibiting high levels of activity and restlessness). However, the classroom teacher may not necessarily be consulted by the medical professionals who make a formal diagnosis of ADHD and plan a treatment strategy for one of their students. This is unfortunate, as teachers often initiate the query of ADHD and have vital input to provide at various stages of diagnosis and treatment.

Suspecting behavioural difficulties

The teacher may be the first to suspect that a child is experiencing behavioural difficulties at school. The teacher can begin a process of observation and data collection to gain more insight into the nature, frequency, and severity of the behavioural problems that the child is experiencing.

Observing student strengths and difficulties

When a teacher first notices a student struggling in the classroom, it is important for him or her to collect information about the student's strengths, needs, and areas of difficulty (for example, academic skill deficits, types of behaviours that are occurring). This information can then be used for two purposes:

  1. The teacher can begin to try different strategies to help the student become more successful in the classroom.
  2. The teacher can inform the parents of his or her concerns about the student's difficulties and share what strategies he or she is currently using to address them.

Given that there are a number of reasons why a child may be experiencing attention and/or hyperactivity symptoms in the classroom, the teacher cannot conclude that the behavioural difficulties are necessarily due to ADHD (see ADHD look-alikes). For example, it is possible that the child has recently experienced a stressful event that is resulting in poor concentration at school. Likewise, it is possible that the symptoms only occur in one subject and are therefore more related to a specific learning disability than to ADHD. However, the teacher can provide an objective description about the child's strengths and needs, including the frequency and severity of the child's behavioural and/or academic difficulties. This information can in turn form the basis of discussion and collaborative problem-solving with the child's parents. It is possible that the child's difficulties may improve after this collaborative problem-solving session. Alternatively, if the student continues to struggle, teachers may suggest that the student be referred to the school team for a more in-depth examination of the child's strengths and needs. This team may also make further recommendations or strategies to help the child in the classroom. School boards may have established referral policies and procedures.23

The diagnostic process

If the student continues to struggle in the classroom, the school team may then prompt a referral to school-based services for a more formal assessment. Parents may also seek help from community-based services (for example, a registered psychologist or a physician) to gain a better understanding of the nature of their child's difficulties.

As mentioned, a clinical diagnosis of ADHD requires that the symptoms are persistent and occur across at least two situations. Therefore, the teacher may be asked to provide clinicians with observational data about the student's behaviour at school, either through behavioural rating scales or through structured telephone interviews.

Treatment and management of students with ADHD

Students with ADHD may receive medical treatment for the disorder. However, it may not help the student in all areas. For instance, research shows that while medication is effective in reducing the behavioural symptoms of many children with ADHD, it does not improve the skills and knowledge that the child may require to achieve academically and socially.17 Thus, by providing information to parents and/or clinicians, teachers can play an important role in monitoring the effectiveness of the medication at school. It is important that parents and teachers work collaboratively to build a strong home-school connection (see Chapter 8) and to coordinate support provided through various systems (including the medical and school systems).

Another key component in effectively managing a student with ADHD is for all involved parties (student, parents, and teachers) to increase their understanding of the condition. Research studies indicate that students benefit when key individuals understand the disorder and are able to provide them with support and encouragement. Figure 1-2 illustrates various steps that could be followed by school boards, starting from the point of concern as raised by a student's teacher, through the referral and assessment process, to intervention and monitoring of treatment outcomes.23

If needed, teachers can also enhance their knowledge and skills through materials such as the TeachADHD DVD, manual, or web site or those listed in the Resources section. For example, information about stimulant medication is provided in brief here.

Figure 1-2: Example of Assessment, Intervention, and Monitoring of Students with Difficulties23

 



1 U.S. Department of Education, Office of Special Education and Rehabilitative Services, Office of Special Education Programs (2003). Identifying and Treating Attention Deficit Hyperactivity Disorder: A Resource for School and Home. Washington, D.C., 20202. Retrieved November 16, 2005, from http://www.ed.gov/teachers/needs/speced/adhd/adhd-resource-pt1.doc

2 Jensen, P.S., Hinshaw, S.P., Kraemer, H.C., et al. (2001). ADHD comorbidity findings from the MTA study: comparing comorbid subgroups. Journal of the American Academy of Child and Adolescent Psychiatry, 40, 147-158.

3 Carroll, J.M., Maughan, B., Goodman, R., & Meltzer, H. (2005). Literacy difficulties and psychiatric disorders: evidence for comorbidity. Journal of Child Psychology and Psychiatry, 46, 524-532.

4 Harpin, V.A. (2005). The effect of ADHD on the life of an individual, their family, and community from preschool to adult life. Archives of Disease in Childhood, 90(1 Suppl), i2-i7.

5 American Psychiatric Association (2000). Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, Text Revision (DSM-IV-TR). Washington, D.C.: American Psychiatric Association.

6 Faraone, S.V., Sergeant, J., Gillberg, C., & Biederman, J. (2003). The worldwide prevalence of ADHD: is it an American condition? World Psychiatry, 2, 104-113.

7 Polanczyk, G.V., Rohde, L.A., de Lima, M.A., et al. (2005). The worldwide ADHD prevalence: a systematic review and meta-regression analysis. Scientific Proceedings of the Joint Annual Meeting of the American Academy of Child & Adolescent Psychiatry and the Canadian Academy of Child & Adolescent Psychiatry (Toronto, Oct 18-23).

8 Kessler, R.C., Chiu, W.T., Demler, O., et al. (2005). Prevalence, severity, and comorbidity of 12-month DSM-IV disorders in the National Comorbidity Survey Replication. Archives of General Psychiatry, 62, 617-627.

9 Curry, J., & Stabile, M. (2004). Child Mental Health and Human Capital Accumulation: The Case of ADHD. National Bureau of Economic Research; Working Paper 10435. Retrieved November 16, 2005, from http://www.nber.org/papers/w10435

10 Rabiner, D., & Coie, J.D. (2000). Early attention problems and children's reading achievement: a longitudinal investigation. The Conduct Problems Prevention Research Group. Journal of the American Academy of Child and Adolescent Psychiatry, 39, 859-867.

11 Warner-Rogers, J., Taylor, A., Taylor, E., & Sandberg, S. (2000). Inattentive behavior in childhood: epidemiology and implications for development. Journal of Learning Disabilities, 33, 520-536.

12 Dulcan, M. (1997). Practice parameters for the assessment and treatment of children, adolescents, and adults with attention-deficit/hyperactivity disorder. American Academy of Child and Adolescent Psychiatry. Journal of the American Academy of Child and Adolescent Psychiatry; 36(10 Suppl), 85S-121S.

13 American Academy of Pediatrics. Subcommittee on Attention-Deficit/Hyperactivity Disorder and Committee on Quality Improvement (2001). Clinical practice guideline: treatment of the school-aged child with attention-deficit/hyperactivity disorder. Pediatrics, 108, 1033-1044.

14 Taylor, E., Sergeant, J., Doepfner, M., et al. (1998). Clinical guidelines for hyperkinetic disorder. European Society for Child and Adolescent Psychiatry. European Child and Adolescent Psychiatry, 7, 184-200.

15 Tannock, R., Hum, M., Masellis, M., et al. (2000). Teacher Telephone Interview Basic Training Manual © 2000. Toronto: Unpublished Manuscript, The Hospital for Sick Children, Department of Psychiatry, Toronto, Canada M5G 1X8.

16 Abikoff, H.B., Jensen, P.S., Arnold, L.L., et al. (2002). Observed classroom behavior of children with ADHD: relationship to gender and comorbidity. Journal of Abnormal Child Psychology, 30, 349-359.

17 The MTA Cooperative Group (1999). A 14-month randomized clinical trial of treatment strategies for attention-deficit/hyperactivity disorder. The MTA Cooperative Group. Multimodal Treatment Study of Children with ADHD. Archives of General Psychiatry, 56, 1073-1086.

18 Brown, T.E. (Ed.). (2000). Attention-Deficit Disorders and Comorbidities in Children, Adolescents, and Adults. Washington D.C.: American Psychiatric Press.

19 Mayes, S.D., Calhoun, S.L., & Crowell, E.W. (2000). Learning disabilities and ADHD: overlapping spectrum disorders. Journal of Learning Disabilities, 33, 417-424.

20 Volk, H.E., Neuman, R.J., & Todd, R.D. (2005). A systematic evaluation of ADHD and comorbid psychopathology in a population-based twin sample. Journal of the American Academy of Child and Adolescent Psychiatry, 44, 768-775.

21 Levy, F., Hay, D.A., Bennett, K.S., & McStephen, M. (2005). Gender differences in ADHD subtype comorbidity. Journal of the American Academy of Child and Adolescent Psychiatry, 44, 368-376.

22 Tannock, R. (2000). Attention Deficit Disorders with Anxiety Disorders. In: T.E. Brown (Ed.), Attention-Deficit Disorders and Comorbidities in Children, Adolescents, and Adults. (pp. 125-170). Washington, D.C.: American Psychiatric Press.

23 British Columbia Ministry of Education. Addressing learning and behavioural differences in the classroom: Some general considerations. Teaching Students with Attention-Deficit/Hyperactivity Disorder. Retrieved November 16, 2005, from http://www.bced.gov.bc.ca/specialed/adhd/address.htm