Attention deficit hyperactivity disorder (ADHD) is the most common childhood behavior disorder. It is characterized by developmentally elevated levels of inattention, impulsivity, and hyperactivity. These three symptoms are so imperative that they have been referred to as the “holy trinity” of ADHD. Over the years, the disorder has gone by a number of different names, including minimal brain dysfunction (MBD), hyperkinesis, hyperkinetic reaction of childhood, and attention deficit disorder (ADD). Regardless of the name, some variation of those three symptoms has been included as a part of the diagnosis. Concerns related to symptoms of ADHD represent 30% to 40% of all psychologically based referrals made to primary care medical practices.
In the past, it was widely assumed that children outgrew ADHD during their adolescent or early adult years. While some individuals do appear to no longer be affected by the disorder once they reach their early 20s, there is increasing evidence that 40% to 60% of children will continue to experience debilitating symptoms of ADHD well into adulthood.
Attention deficit hyperactivity disorder negatively affects not only the affected individual, but also those around him or her. Consequently the assessment and treatment of ADHD needs to be comprehensive and systemic. Research suggests that pharmacological and behavioral treatments are quite effective in reducing the severity of the symptoms and resulting negative effects. In addition, individuals receiving treatment are less likely to develop additional psychiatric disorders as they get older.
Prevalence of ADHD
While there is variability in the estimated prevalence of the disorder, most researchers agree that ADHD affects between 3% and 7% of the school-age population. The reported prevalence differences likely reflect variations in assessment methodologies, such as sampling procedures, assessment instruments, and diagnostic criteria. For example, the estimates of affected children tend to be inflated when sampling procedures do not assess for the degree of functional impairment. There is currently limited information regarding the prevalence of ADHD in adults, but based upon extrapolations from childhood estimates, some researchers have suggested that ADHD affects between 2% and 6% of the adult population.
Prevalence variation also appears to be related to gender. There is a large body of empirical evidence to suggest that males are much more likely to be diagnosed with ADHD than females. Estimated male-to-female ratios for the disorder range from 2:1 to 9:1 depending upon the setting (community sample vs. clinic referred sample). It also appears that the gender discrepancy is lower for individuals with the predominantly inattentive subtype of ADHD.
ADHD Diagnostic Criteria
The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM—IV—TR) specifies 18 symptoms that compose the disorder. Nine of the criteria are related to symptoms of inattention, and nine are related to symptoms of hyperactivity/ impulsivity. Symptoms of inattention include failure to pay attention, having difficulty with sustained attention, not listening, not following through on instructions, poor organization skills, avoiding tasks requiring sustained mental effort, often losing things, being easily distracted, and being forgetful. Symptoms of hyper-activity include fidgeting often, getting out of one’s seat at inappropriate times, behaving or feeling restless, not being able to play quietly, being compelled to be active, and talking excessively. Symptoms of impulsivity include blurting out answers, having difficulty awaiting one’s turn, and interrupting others.
Based upon this cluster of symptoms, three primary subtypes of ADHD can be diagnosed. If an individual exhibits six of the nine inattention symptoms for a period of at least 6 months, and if these exhibitions are both maladaptive and inconsistent with the individual’s developmental level, the diagnosis of attention deficit/hyperactivity disorder, predominately inattentive type can be made. If an individual exhibits six of the nine hyperactivity/impulsivity symptoms for at least 6 months and to a maladaptive degree given the individual’s developmental level, the diagnosis of attention deficit/hyperactivity disorder, predominately hyperactive-impulsive type can be made. If an individual exhibits significant elevations on six of the inattention symptoms and six of the hyperactive-impulsive symptoms, he or she could be diagnosed with attention deficit/hyperactivity disorder, combined type. In all of the subtypes of ADHD listed above, some symptoms causing impairment must have been present before the age of 7, some impairment from symptoms needs to be present in two or more settings, and there needs to be clear evidence of significant impairment in social, academic, or occupational functioning. In cases where it is unclear if these criteria have been met, a diagnosis of attention-deficit/hyperactivity disorder, not otherwise specified could be made.
The final criterion to consider is that the symptoms could not be better accounted for by another mental disorder. This is a very important criterion to consider. Symptoms characterized by inattention, impulsivity, and hyperactivity can occur in numerous other mental disorders. The clinician needs to consider not only that the individual has some disorder other than ADHD, but that the individual has another disorder in addition to ADHD.
Making the Diagnosis
When making the diagnosis of ADHD, the clinician has a number of different tools to choose from. First are the DSM-IV ADHD rating scales. These scales take the DSM-IV criteria and have parents or teachers rate a child’s behavior on a Likert-type scale. These specific scales tend to be relatively brief and easy to administer and have adequate psychometric properties.
The second type of assessment instrument is the broad-band rating. These instruments assess for a broader array of behaviors than just those associated with ADHD. Examples of commercially available instruments that would fall into this category include the Child Behavior Checklist (CBCL) and the Behavior Assessment System for Children-2nd Edition (BASC-2). Both of these instruments assess for a broader range of symptoms, including depression, aggression, and somatic complaints. These instruments are well normed, have acceptable psycho-metric properties, and are available in parent, teacher, and self-report versions. Research suggests that youth self-report versions are rather poor at differentiating between children with ADHD and controls, suggesting that children may not be accurate informants of their behavior problems. In addition studies suggest that when there are discrepancies between parents’ and teachers’ perceptions on such instruments, teachers tend to be the more accurate informants. The reason for this is that teachers usually have a better understanding of child development and age-appropriate behavior than many parents do.
Structured and semistructured interviews are a third type of assessment tool that can be employed when making a diagnosis for ADHD. These instruments have advantages over rating scales in that the clinician can follow up on parent ratings and ensure that the parent understands the intent of the question. However, interviews are time intensive for both the examiner and the informant (usually the parent). The Diagnostic
Interview for Children and Adolescents-Revised (DICA-R) and the Diagnostic Interview Schedule for Children-Version IV (DISC-IV) are two of the more widely used diagnostic interviews that have adequate psychometric properties.
Impairment rating scales are a fourth category of assessment for ADHD. Some measures provide documentation for global or overall impaired psychosocial functioning (e.g., the Children’s Global Assessment of Functioning), whereas others provide a multidimensional rating of impairment (e.g., the Child and Adolescent Functional Assessment Scale). Some of the more widely used impairment rating scales show good temporal stability and interrater reliability. In addition they also have evidence for convergent and concurrent validity.
A fifth category of assessment is observational measures. There is a long tradition of conducting observations for children with behavior disorders. Observations can occur in analogue or naturalistic settings. Observation measures can be very complex and assess multiple behaviors across multiple settings or can be relatively simple and involve the assessment of only a couple of behaviors (e.g., verbal intrusions and out-of-seat activity in the classroom). Studies have shown that when the behaviors for observation are carefully chosen, observation measures that involve relatively few behaviors can be as effective as the more comprehensive systems.
Physiological or laboratory measures form a final category of assessment. While no such measures can diagnose ADHD, some are widely used to aid in making the diagnosis. One group of such measures is the continuous performance tests (CPTs). There are many different types of CPTs available; some of the more common commercially available ones include the Test of Variables of Attention (TOVA), Conner’s CPT, and the Individual Variables of Attention (IVA). All CPTs attempt to provide a computerized assessment of inattention, response inhibition (hyperactivity), and reaction time (impulsivity). While studies have shown that individuals with ADHD do perform more poorly on these tests than do controls, individuals in other clinical groups (e.g., learning disabilities, depressed) also perform more poorly than controls.
Some researchers have argued that when assessing for ADHD, less emphasis should be placed on identifying symptoms that confirm the diagnosis and more emphasis should be placed on evaluating the function of the behavior that is causing the problems. Through functional behavioral analysis, clinicians are better equipped not only to recognize the maladaptive behaviors but also to implement a strategy to treat them.
When compared to children of similar age and gender, children with ADHD experience functional and adaptive impairment academically, behaviorally, and socially. The core symptoms of inattention, impulsivity, and hyperactivity can manifest in various ways. Attention is frequently defined by a set of observable behavioral characteristics. For example, children with ADHD may find it difficult to remain focused on an assignment with ongoing distractions. Each passing moment may present a challenge for them to focus on a particular stimulus. Furthermore, once distracted, these children are often slower to return to task. Factors such as background noises, their own thoughts, and activity of any kind present potential distractions, which may preclude the child from staying on task. Adults working with these children frequently report that the children appear to be daydreaming, lethargic, or prone to not listening to instructions.
Impulsivity represents the inhibitory deficits an individual exhibits. These problems are associated with the tendency to interrupt others, to call out answers before the speaker can finish a question, and to have trouble waiting one’s turn. Frequently, children with ADHD report acting without considering the consequences for their behavior. Problems with low frustration tolerance and temper outbursts may be related to impulsivity. Some researchers, such as Russell Barkley, consider impaired inhibition to be the paramount symptom associated with ADHD.
Hyperactivity is the third component of the ADHD triad. When compared to normal controls, children with ADHD are significantly more active. Often this activity appears aimless, as if the child is compelled to be doing something. This tendency may also result in the child engaging in more high-risk behaviors, such as running into the street without looking or jumping from a fast-moving object. These risk-taking behaviors appear to persist in adulthood. Adults with ADHD have been found to be more prone than controls to substance abuse, traffic accidents, and legal problems.
Frequently, a child with ADHD will first exhibit problematic behavior at school. Teacher-student relationships are often marked by strain and significant discord. Children with ADHD frequently engage in disruptive behavior, refuse to follow directions, and fail to complete assignments. Observers often misinterpret such a child’s dislike for tasks that require sustained attention as an indication that the child is lazy or immature. Additionally, when compared to peers, children with ADHD tend to lose necessary materials and have more organizational difficulties. Consequently parents and teacher may view them as being oppositional and defiant. These behaviors often result in increased disciplinary referrals, lower academic achievement, and more school failure.
Parents of children with ADHD frequently experience problems relative to parenting practices, parent-child interactions, and parenting stress. They frequently exhibit higher levels of stress than parents of controls. In addition, there is a greater chance of disagreement between parents relative to child-rearing practices. Mothers of children with ADHD are more likely to be depressed, and fathers are more likely to have substance abuse problems, than parents of controls.
Parent-child interactions are frequently marked by conflict. Research suggests that these parents are more likely to engage in punitive parenting practices. Perhaps in response to these conflicted interactions, children with ADHD become even more overactive, defiant, uncooperative, and impulsive. This further exacerbates the parent-child conflicts. There is some research to suggest that the use of harsh physical discipline is associated with the development of oppositional defiant disorder or a conduct disorder in children with ADHD. Older adolescents and young adults who received harsh physical punishment as children appear to be more impaired than their ADHD peers whose parents did not use such practices.
In addition to negative family interactions, peer relationships also tend to suffer. Children with ADHD interact less with playmates during conversation, tend to be more bossy, exhibit a diminished receptivity to social cues, and appear less likely to engage in close friendships. The aforementioned problems are exacerbated when there is a comorbid oppositional defiant or conduct disorder.
Low self-esteem has been observed more frequently in children with ADHD than in controls. In an effort to preserve their self-esteem, children with ADHD may overestimate their performance in the domains with greatest deficits. So, a child with ADHD who is struggling in school may exaggerate his or her academic achievement for the purpose of self-protection.
When a child has ADHD, he or she is more likely than not to have a comorbid disorder. Recent research suggests that up to 87% of children with ADHD have at least one comorbid condition and up to 67% have at least two. Approximately half of children with ADHD will go on to develop another behavior disorder such as oppositional defiant disorder or conduct disorder. Other common comorbid conditions include the following: learning disability (40% to 60%), depressive disorder (17% to 30%), anxiety disorder (20% to 43%) and substance abuse disorder (18% to 36%). There is some evidence to suggest children with ADHD may be more likely to develop juvenile-onset bipolar affective disorder. While half of the individuals with Tourette’s syndrome have ADHD, children with ADHD do not appear to be more likely to develop Tourette’s.
Etiology of ADHD
There are numerous hypotheses relative to the etiology of ADHD. However, few are supported with empirical research. One of the theories that has some support surmises a strong biological component. The evidence for a genetic influence in ADHD has been gathered from family studies, twin studies, and molecular genetics studies. From the research relative to families, there are data that suggest that parents with an ADHD diagnosis are more likely than non-ADHD parents to have children with the same disorder. In fact, some researchers assert that there is a 57% chance that parents with ADHD will have children with the same diagnosis.
Researchers have also looked at the prevalence of the disorder in parents of children who have been diagnosed with ADHD. These studies found that 15% to 20% of the mothers and 20% to 30% of the fathers of an affected child also have ADHD. There is also a 1 in 3 chance that a child with ADHD will have a sibling who also has the disorder. Identical twins also appear to have increased risk for ADHD. However, with these studies it is difficult to tease out environmental contributions to the expression of the disorder. Gonzales-Limas suggested that 70% to 95% of the trait variability among individuals with ADHD can be accounted for with genetic heritability. Researchers involved in molecular genetics research believe that several genes are related to risk for ADHD. These genes include DAT1, DRD4, and DHB.
Some studies have found that birth complications may increase the likelihood that a child will develop ADHD. In addition, several studies suggest a link between premature birth or low birth weight and ADHD. In fact, it has been estimated that low birth weight is associated with 14% of all ADHD diagnoses. Maternal behaviors such as smoking and using drugs or alcohol during pregnancy have also been linked to low birth weight and increased risk for ADHD.
Several environmental variables have been consistently implicated in the expression of ADHD. Correlations between exposure to environmental toxins, such as lead, and hyperactive behaviors have been reported in numerous studies. Other environmental variables may include malnutrition, disease, and trauma. Several large, well-controlled studies that systematically evaluated the diets of children for the effects of additives such as processed sugar, wheat germ, and food dyes on the development and expression of ADHD have failed to find significant differences between groups of children who were exposed to the additives and those who were not.
Stimulant medications are one of the most widely used and oldest treatments for ADHD. In fact, stimulants have been used to treat ADHD since the mid-1930s. The therapeutic mechanism of action relative to stimulant medications is not precisely understood. Data generated from a large body of research suggest that stimulants increase neural activity in some parts of the brain; in others areas stimulants actually inhibit neural activity. Stimulant medications have been shown to be effective at increasing an individual’s ability to focus attention and to inhibit impulsivity. It has been estimated that up to 82% of children over the age of 5 with ADHD have a positive response to stimulant medication. However, a growing body of research suggests that persons who do not respond to standard stimulant medication may respond positively to low doses of amphetamines.
The use of stimulant medications does come with negative side effects, including loss of appetite and difficulty sleeping. In addition, the benefits from stimulants may be relatively short-term. Some have estimated that stimulants lose their effectiveness within 5 years. Given the potential contraindications and limited longevity of psychotropic interventions, prescriptions must be issued judiciously. Physicians can usually adjust the doses of the medications to alleviate most side effects, and children frequently take “drug holidays” during the summer months to decrease the likelihood that a child will develop a tolerance to the medication. While stimulant medications have been shown to be effective in treating ADHD, multiple studies have shown that optimal treatment effects result when individuals receive pharmacological intervention paired with behavioral interventions.
Behaviorally based treatment plans are commonly used in clinics, schools, and day treatment centers to treat children with ADHD. Numerous behavioral interventions exist; however only parent-training programs and classroom-based treatments have been supported by evidence-based research. Many behavioral interventions are based upon an antecedent, behavior, and consequence (A-B-C) paradigm. According to this theory, all behaviors (B) are preceded by environmental variables (A), and the positive or negative reactions children receive from that behavior (C) will determine whether a given behavior will increase, decrease, or remain unchanged. Behavior management programs that identify target behaviors and provide for the contingent application of positive or negative consequences is the most common manifestation of behavioral interventions. For adults with ADHD, self-management procedures that involve self-monitoring, stimulus control, and self-reward are often used.
Parent-training programs are a common, well-researched, and efficacious treatment for ADHD. Some examples include Cunningham’s Community Parent Education (COPE), Eyberg’s Parent-Child Interaction Therapy (PCIT), and Barkley’s Parent Training Program. These parent-training programs have all been subject to research and are widely used. The methods and rationales associated with parent training programs are usually very similar: they endeavor to teach parents how to shape their child’s behavior with appropriate behavioral management techniques.
The majority of parent-training programs include psychoeducational sessions. In these sessions, parents are provided with information about ADHD (e.g., prognosis, course, and etiology). These sessions may be supplemented with handouts, books, or videotapes. Providing parents with information about ADHD improves their perceptions of their children and may improve treatment outcomes.
In addition to the general overview of ADHD, parents are also taught the basic principles of behavioral modification. Attending skills are also a critically important component of these programs. Attending skills refer to a process in which the parent listens, provides positive attention, and ignores mild undesirable behaviors exhibited by the child. Frequently these attending skills are practiced in a low-stress, play-based setting. Attending skills represent the cornerstone of behavioral modification; however, by themselves these skills will not effectively shape the target behaviors. Therefore, parent training focuses on several other aspects of parenting. Often parents are required to completely change the manner by which they interact with their children. This is because many parents appear to overfocus on undesirable behaviors and neglect to acknowledge when desirable behaviors occur. Parent training teaches parents to listen more effectively, shift the focus of attention from undesirable to desirable behavior, consider developmental variables, and issue frequent positive reinforcement.
The success or lack thereof associated with any parenting intervention is predicated upon the quality of the parent-child relationship. Parents are often encouraged to examine the quality of the relationship they have with their children and to identify conditions that negatively impact their relationship. Parents begin to explore the relationship between their children’s behavior problems and their own reactions when the children misbehave. For example, a parent may unintentionally reinforce an undesirable behavior; this often occurs when parents attend primarily to undesirable behavior and overutilize punishment. During this critically important phase, ineffective parenting practices are identified and replaced with more efficacious methods.
Skilled use of reinforcement is quintessential to successful behavioral change. There are several prerequisites to the implementation of a reinforcement system. First, the parent must identify, define, and communicate behaviors in clear, specific, and measurable terms. Furthermore, whenever possible, the goals should be articulated with positive language and focus on the behavior that the child will exhibit, rather than what the child will cease to exhibit. A special type of reinforcement is praise. Parents learn that if they want to modify their child’s behavior through praise, they should use specific-labeled praise. This means the parent makes sure that the child knows exactly why he or she is being praised. So instead of saying “You’re a big boy,” the parent learns to say, “You got up and got dressed all by yourself. Thank you for helping. You are such a big boy.”
The second technique, punishment, must be implemented judiciously, and parents should always remember that reinforcement results in more enduring behavior change. In parent training (and behavior modification programs), a specific form of punishment called response cost is also used to shape behavior. Response cost refers to the removal of some privilege when the child exhibits an unwanted behavior. So, a child may lose his or her video game privileges for the evening if he or she chooses to neglect the dishes. Again, it is critically important that parents implement punishment strategies with caution. Unfortunately if parents want to stop a behavior quickly, the use of punishment is the fastest way to do so, but that change tends to be short-lived. Long-term behavior change occurs best with reinforcement.
Another effective behavioral intervention, time-out, is conceptually similar to response cost. While response cost results in the removal of a privilege, time-out results in the removal of positive reinforcement. Like response cost, time-outs should be utilized sparingly. Some researchers suggest that time-outs be limited to as few as two predetermined noncompliance behaviors. Similarly, the location and amount of time spent in timeout for a given offense should be predetermined. Children should be required to correct the behavior that actuated the time-out; in addition, the child should be rewarded for positive behavior. While a common rule of thumb for the length of time to keep a child in time-out is 1 minute for each year of age, research suggests that time-out achieves maximal impact for children in 3 to 5 minutes, regardless of their age.
The token economy represents another popular technique, which utilizes both reinforcement and response cost. As with the other techniques, the focus of the token economy should be on positive behavior.
A complete explanation of the token economy would exceed the scope of this entry, so only basic principles will be addressed.
Token economies are often used when the child requires frequent reinforcement. A list of target behaviors—following the guidelines relative to positive reinforcement—is generated. These behaviors should be clear, concrete, and measurable. Next, parents, teachers, or helping professionals issue tokens (usually plastic chips) or points (recorded in a notebook or calendar) when the child exhibits desirable behavior. The tokens or points are taken away when the child engages in undesirable behaviors. After a predetermined period of time, the child is allowed to exchange tokens or points for a privilege (e.g., extra time playing video games) or some other reinforcing product (e.g., comic book, candy bar).
- American Academy of Child and Adolescent Psychiatry. (1997). Practice parameters for the assessment and treatment of children, adolescents, and adults with attention-deficit hyperactivity disorder. Journal of the American Academy of Child and Adolescent Psychiatry, 36(suppl), 82-121.
- American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders (4th ed., Text rev.). Washington, DC: Author.
- Anastopoulos, A. D., Barkley, R. A., & Shelton, T. L. (1997). Family based treatment: Psychosocial intervention for children and adolescents with attention deficit hyperactivity disorder. In E. D. Hibbs & P. S. Jensen (Eds.), Psychosocial treatment research of child and adolescent disorders (pp. 267-284). Washington, DC: American Psychological Association.
- Barkley, R. A. (2004). Adolescents with ADHD: An overview of empirically based treatments. Journal of Psychiatric Practice, 10, 39-56.
- Barkley, R. A. (2006). Attention deficit hyperactivity disorder: A handbook for diagnosis and treatment (3rd ed.). New York: Guilford Press.
- Brinkmeyer, M. Y., & Eyberg, S. M. (2003). Parent-child interaction therapy for oppositional children. In A. E. Kazdin & J. R. Weisz (Eds.), Evidence-based psychotherapies for children and adolescents (pp. 204-223). New York: Guilford Press.
- DuPaul, G. J., & Stoner, G. (2003). ADHD in the schools: Assessment and intervention strategies. New York: Guilford Press.
- Frick, P. J., Lahey, B. B., Applegate, B., Kerdyck, L., Ollendick, T., Hynd, G. W., et al. (1994). DSM-IV field trials for the disruptive behavior disorders. Symptom utility estimates. Journal of the American Academy of Child & Adolescent Psychiatry 33, 529-539.
- Johnston, C., & Mash, E. J. (2001). Families of children with attention-deficit/hyperactivity disorder: Review and recommendations for future research. Clinical Child and Family Psychology Review, 4, 183-207.
- Johnston, C., & Murray, C. (2003). Incremental validity in the psychological assessment of children and adolescents. Psychological Assessment, 15, 496-507.
- Pelham, W. E., Fabiano, G. A & Massetti, G. M. (2005). Evidence-based assessment of attention deficit hyperactivity disorder in children and adolescents. Journal of Clinical Child and Adolescent Psychology, 34, 449-476.
- Pelham, W. E., Wheeler, T., & Chronis, A. (1998). Empirically supported psychosocial treatments for attention deficit hyperactivity disorder. Journal of Clinical Child Psychology, 27, 190-205.
- Weiss, G., & Hechtman, L. T. (1993). Hyperactive children grown up (2nd ed.). New York: Guilford Press.
- Wender, P. H. (1995). Attention-deficit hyperactivity disorder in adults. New York: Oxford University Press.