SEMINAKS I N NEUKOLOGY-VOLUME

11, NO. 1

MARCH 1991

Role of Attention Deficit Hyperactivity Disorder in Learning Disabilities

T h e referral of'children, usually boys, with the complaint of inattentive, disruptive behavior, most typically in school but often in other social settings, has become a major part of the practice of child neurology. It appears certain that this is not a new entity, but it is only in the last 40 years that it has been conceptualized as a medical problem that can be treated with medication. Neurologists have always been aware that events that produce brain injury can change behavior and often produce impulsivity, difficulty with concentration, and emotional lability. In 1966, a task force of the National Institute of Neurological Diseases and Blindness developed the concept of minimal cerebral dysfunction, and included both hyperkinetic behavior and learning disabilities as part of the spectrum.' T h e implication of this diagnostic term was that minor degrees of brain injury could produce clinical phenomena similar to those caused by major traumata. T h e term "minimal cerebral dysfunction" was useful in focusing attention on a troublesome group of patients, but demonstrated poor validity when it was critically examined. T h e construct was so global that it was of little clinical use and has largely been abandoned. In 1980, the third edition of the Diagnostic and Statistical Manual of Psychiatric Disorders (DSM-111) introduced the term "attention deficit disorder" (ADD).' T h e diagnostic criteria required that the symptoms begin prior to age 7 years. Boys are affected five to ten times as frequently as girls. Key clinical features were inattention and impulsivity; the diagnosis was made when a sufficient number of descriptors listed in DSM-111 fitted the patient. A third feature, motor

hyperactivity, could also be added to the diagnostic constellation (ADD-H), but this was not required. T h e recent revision of DSM-111 (DSM-111-K) has changed the name of the condition to attention deficit hyperactivity disorder (ADHD) and has modified the diagnostic criteria by removing the three behavioral groupings and listing 14 descript o r ~ T. ~ h e diagnosis is made when eight or more of these features are manifested by the patient. In clinical practice it is easier to use the original DSM111 criteria, and they form an excellent framework for obtaining information from the child's parents and teachers.

DIAGNOSIS AND DIAGNOSTIC PITFALLS There are two critical points to remember when a diagnosis of ADHD is considered. T h e first is that the child's attention span and level of impulsivity must be measured against what is age appropriate. Second, there are no biologic markers for the condition: the diagnosis must be made entirely on the basis of clinical criteria. A careful history is the starting point in the diagnostic process. This should be supplemented by information from the child's teacher, if the child is in school, o r other adults with whom the child interacts. If the troublesome behavior occurs in only one setting, the diagnosis of ADHD is unlikely, and it is important to determine what interactions trigger the problem. Checklists and rating scales provide a useful way of structuring descriptions of the child's behavior and semiquantitative data that can be useful for monitoring treatment effe~ts.~.%ehavior in the

Director, Boling Center for Developmental Disabilities, Shainberg Prokssor of Pediatrics, and Professor o f Neurology, Memphis, Tennessee Reprint requests: Dr. Golden, Boling Center for Developmental Ilisabilities, 7 1 1 Jefferson Avenue, Memphis, 'TN Copyright O 1991 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, N Y 10016 All rights reserved.

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Gerald S. Golden, 111.0.

VO1,UME 1 I , N U M B E K 1 ,\/IAKCII 1991

physician's office is not a good index of ADHD. quently have low self-esteem, poor social skills, and Most children are highly anxious in this setting, academic underachievement. and many are able to control their hyperactive beIn summary, the diagnosis of ADHD is not havior. easy and is not one that lends itself to easily valiThe physical examination is useful only in dated diagnostic criteria. A conservative approach helping to eliminate conditions that could interfere is recommended, especially if an attempt at mediwith the child's ability to attend to environmental cal treatment hinges on the diagnosis. stimuli and to concentrate on the task at hand. Deficits in vision and hearing are the most important. Any chronic medical condition can also interfere NEUROBIOLOGY with attention span. In addition, it is important to obtain an assessment of the patient's developAttempts to define a biologic basis for ADHD mental level, because attention span should be have been consistently unsuccessful.'" The neumeasured against the norms for mental age, not roanatomy of the brain, as demonstrated by neuchronologic age. roimaging studies, is normal. No neuropathologic There is an extensive literature on "soft neu- substrate has been demonstrated, although this is rologic signs," deficits in coordination and skilled an area that has not been studied intensively. Abmotor acts that are abnormal only as a function of normalities in neurophysiologic studies are similar the child's age and that do not imply underlying to those found in any condition associated with imfocal neurologic disease. These signs are nonspe- paired attention; they are not specific to ADHD.14 cific and have little or no usefulness in the diagT h e therapeutic response to psychostimulant nosis of ADHD.G,7Neurodiagnostic studies such as drugs implies the possibility of a defect in one of electroencephalography and neuroimaging proce- the monoaminergic systems of the brain. Analysis dures also have no value. Children with poor abil- of the studies published to date, however, indicates ity to sustain attention do have abnormalities in vi- no consistent findings.lVhe possibility of a gesual evoked responses, but this phenomenon has netic basis underlying ADHD is also unresoived. little use outside of the research laboratory. The family history often reveals the presence of There is an important differential diagnosis similar symptoms in the boy's father, but this may that must be considered."Qepression can inter- represent only a generalized increase in psychofere with attention in a child, just as it can in an pathology in families of children with ADHD. adult. The diagnosis of depression in children is a It has been suggested that exposure to certain difficult one, because the classic symptoms may not toxins prenatally or in early life can produce be present. It should be considered in any child ADHD. ADHD and learning disabilities have been who developed symptoms suggesting ADHD sud- reported in the fetal alcohol syndrome."' There is denly, or if the symptoms first appeared when the also evidence that low-level lead exposure can be child was older than 7 years. Depression should associated with learning problems and possibly also be considered if there is a family history of ADHD.17 If these correlations can be documented affective disorder. Symptoms of mania are rare consistently, it will provide a powerful tool to use in children but can be confused with those of to attempt to understand the nature o f t h e underADHD.IOHere again, the diagnostic clue is a fam- lying brain dysfunction. The inability to define a single underlying bioily history of affective disorder. Drug abuse may also present with symptoms of ADHD. This prob- logic basis for this symptom complex and the var-ilem should be considered in any child with a late ety of brain lesions that can cause similar behavior imply that ADHD is probably best thought of as onset of signs of the disorder. A major problem in differential diagnosis is being a symptom complex, not a specific disorthe overlap of ADHD and conduct disorder. T h e der.13 Such a hypothesis, if proven, would lead to essential features of conduct disorder are persis- further analysis to attempt to define discrete tent violation of the rights of others and violation subgroups. This would then have important implications for treatment and for attempts to define of age-appropriate rules and norms of behavior." Children with this condition demonstrate physical the prognosis for individual children. aggression, poor frustration tolerance, irritability, and temper outbursts. Academic achievement is frequently impaired. Rating scales completed by TREATMENT both parents and teachers show strong cross-correlations between features of conduct disorder and T h e treatment of a child with hyperactive bethose of ADHD." Children with ADHD also fre- havior or attention problems in school should be-

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growth rate may occur, especially at higher dose levels. Apparently there is complete catch-up of growth and weight during drug holidays.22 An increased heart rate and blood pressure following methylphenidate administration have been reported, but the functional significance of these findings is not clear.'" Some patients develop adverse behavioral reactions on this medication. This rarely takes the form of increased hyperactivity. More commonly, the patient develops dysphoria, depression, blunting of affect, and loss of motivation. This reaction is most common in young children, especially those less than 5 years of age. The most serious side effect of all of the psychostimulants is their ability to precipitate or exacerbate Tourette syndrome. Approximately 1.3% of patients given these drugs will develop a tic, although the movements generally disappear when the drug is d i s ~ o n t i n u e dIn .~~ other cases, the onset of Tourette syndrome occurs, and treatment for the new disorder has to be c o n ~ i d e r e dThis . ~ ~ phenomenon seems to be most likely if there is a family history of tics, implying that it occurs in individuals who carry the gene for Tourette syndrome. If psychostimulants are given to a patient who already displays tics, they worsen in approximately one third of cases.'" If the child with ADHD has tics or a family history of tics, it is most important to be certain that behavioral approaches to treatment of the behavior problem have been exhausted before medication is begun. The onset or worsening of tics after the introduction of the psychostimulant calls for a careful reanalysis of the severity of the ADHD and the tics, and a decision as to what is the child's most significant problem. Treatment can then be planned on the basis of this decision. Options include discontinuing the medication or continuing methylphenidate and accepting the tic disorder. Alternative drugs such as clonidine or tricyclic antidepressants may be tried. In some cases drug therapy for both ADHD and the tic disorder may be necessary. This represents a common problem in practice, because approximately one third of patients with Tourette syndrome have clinical features of ADHD.'7 Pemoline has the advantage of a long duration of action so that it need be administered only once daily. A disadvantage of this drug is that a therapeutic effect may not be seen for as long as 3 weeks after it is begun, making it difficult to determine rapidly if there is a therapeutic effect and to titrate the dose. The usual starting dose is 37.5 mg daily. This can be increased by 18.75 mg every 7 days until a maximum dose of 112.5 mg daily is

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gin with behavioral and environmental modification." T h e classroom setting should be one that minimizes distractions and maintains a regular routine. Two important techniques to use with the child are positive reinforcement for staying on task and completing assignments, and breaking up assignments into small enough chunks that the child can achieve successful completion. As the child is reinforced for completing shortened assignments, they can be gradually increased in length. The parents must also be part of the behavioral program so that there is consistency of expectations and methods used to help the child succeed. If the diagnosis of ADHD seems secure, and if behavioral approaches are not adequate, treatment with medication may then be considered. The most commonly used drug is methylphenidate, although pemoline and dextroamphetamine are also useful.'!' Methylphenidate has a rapid onset of action, but is not an easy drug to use because the duration of its therapeutic effect is approximately 4 hours. This means that doses must be taken with breakfast and lunch to get the child through the school day. Behavior at home later in the day may be a problem, and it may be difficult for the child to complete his homework when the drug effect has dissipated. Some children require a third dose, but this may cause insomnia at bedtime. A sustained release preparation is available, but its duration of action is unpredictable. The decision to begin medication should be based on the diagnosis and its severity, for the response to the drug cannot be used to validate the diagnosis. Normal boys as well as those with ADHD show similar changes when given a single dose of a psychostimulant."' The baselines and degree of change are different in the two groups, but each group demonstrates decreased motor activity, increased attentiveness, and increased performance on a short-term memory test. The optimal single dose of methylphenidate is 0.3 to 0.6 mglkg. There is some evidence that doses as high as 1 mglkg may actually interfere with cognitive performance, although there is increased control of behavior." Part of the drug treatment program should be a careful analysis of the target symptoms being treated; the teacher and parent should report regularly to allow monitoring of the effects of the drug. Some investigators have recommended a trial of a placebo before introducing the active drug, but this approach is not widespread in practice. Methylphenidate has been associated with remarkably few serious adverse side effects. Insomnia is not common unless a dose is given late in the day. Appetite suppression, weight loss, and slowed

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reached. The side effects of pemoline are similar as well as intraventricular conduction defects.:" to those of methylphenidate. These parameters should be monitored if high Dextroamphetamine has been prescribed less dose levels are used. Clonidine has been used for commonly in the past 20 years as it developed a treatment of ADHD also. This drug has been recreputation as a drug that was frequently abused. ommended especially for the child with ADHD The usual dose is 5 to 40 mg daily. Dextroamphet- and a tic d i ~ o r d e r . There "~ is some controversy as amine, like methylphenidate, has a short duration to how often the drug is useful for either condiof action, but a sustained release form is available tion. and appears to be useful. Side effects are shared Special diets that restrict sugar intake, remove with methylphenidate and pemoline. food additives and coloring agents, or provide supThe question of the advisability and timing of plements of high doses of vitamins or minerals (ordrug holidays raises some controversial issues. thomolecular therapy) have been reported to proWhen treatment is started, it probably should be duce improvement in the symptoms of ADHD. continued on a daily basis, including weekends. None of these treatment approaches has been There may be a transient rebound effect with in- shown to be useful in well-designed double-blind creased hyperactivity when the drug is discontin- tests, and they cannot be recommended as part of ued, and it would be inappropriate to subject the the therapeutic arrnamentari~m.'~Wespite the lack child to this at the end of each week. If the child's of a scientific basis for these dietary manipulations, problem is mainly inattention and not motor hy- up to 8% of pediatricians use the additive-free diet peractivity, however, treatment only on school days and 12% recommend restriction of sugar.'" Only may be suitable. Long breaks in the school year, 1% prescribe megavitamins. such as summer vacation, are the appropriate times to try to discontinue the medication. Every attempt should be made to keep the child free of medication for at least 2 to 3 weeks to be certain ADHD AND LEARNING DISABILITIES that the return of troublesome behavior does not merely represent a rebound. If the drug holiday is Children with behavior that shows the diagsuccessful, the child should enter the next school nostic features of ADHD also commonly display year without medication to determine if the need academic underachievement or failure. In many is no longer present. cases, the poor school performance is the result of ~ s ~ c h o s 6 m u l adrugs nt have been clearly dem- a learning disability. It has been estimated that beonstrated to improve the acceptability of behavior tween 50 and 80% of children with ADHD have in the classroom and at home.28Measures of atten- learning disabilities."Reading disorders are the tion improve and impulsivity is decreased. Discon- most common. The percentage of children with tinuation of the drug causes a return to pretreat- learning disabilities who also have ADHD has not ment levels of inattention and impulsivity, but been determined. T h e relationships, if any, bebehavioral scores by parents and teachers remain tween ADHD and learning disabilities are complex higher than at baseline. Vigilance will also improve, and controversial. but only in those children who had abnormal preThere are four separate possibilities to explain drug scores. Rating scales and narrative reports these relationships: consistently document these effects. It is not as 1. Both are high incidence disorders and their easy to demonstrate positive changes in cognitive co-occurrence is only by chance. function or school performance, however, and the 2. Underlying brain dysfunction is responsiavailable evidence suggests that the long-term outble for both the ADHD and the learning discome for academic achievement is not ~hanged.~!'.~" ability. A number of other classes of drugs have been 3. ADHD interferes with the child's ability to used to treat ADHD. Tricyclic antidepressants attend and learn. seem to be increasing in popularity, and some re4. Academic failure, resulting from the learnports indicate efficacy similar to that of the more ing disability, causes secondary behavior probcommonly used psychostimulants. Improvement lems that are manifested as ADHD. in symptoms of ADHD has been demonstrated in Sufficient data are not available to allow the approximately 70% of patients treated with desi- first possibility to be addressed. This would require pramine."' At doses above 3.5 mglkglday, there knowing the exact incidence of the two conditions were some cardiovascular effects, which did not separately and how frequently they occur together. seem to be clinically significant. These included in- Without more highly replicable and agreed on dicreases in diastolic blood pressure and heart rate, agnostic criteria, this task is impossible.

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lem and may get less individualized attention than was originally available.

PROGNOSIS As previously noted, the use of psychostimulants in children with ADHD is consistently associated with short-term improvements in behavior, attention, control of impulsivity, and vigilance. Long-term studies of behavior, however, do not suggest as optimistic a picture. Conduct disorders, antisocial personality disorder, and substance abuse are more frequent in adolescents who previously were diagnosed as having ADHD than in a control group. One predictor of this negative outcome was the presence of aggressive and unsocialized behavior in the younger child. "Pure" hyperactivity, unassociated with a conduct disorder, did not have an adverse prognosis."" There is some suggestion that a better outcome is seen if drug treatment has been used, but the evidence is not c o n c l ~ s i v eT. ~h~e subgroup of children with ADHD and conduct disorder needs an intensive treatment approach, which includes, in addition to medication (if used), psychiatric treatment and family counseling. Family and social variables may play a critical role in setting the longterm p r o g n ~ s i s . ~ ' The issue of ADHD continuing into adolesence and adulthood is assuming increased importance in the literature and in clinical pra~tice."~' Follow-up studies have shown that one third of children who have ADHD diagnosed in childhood still meet the diagnostic criteria as adolescent^.^" An additional 5% meet the diagnostic criteria of ADHD, residual state. This is defined in DSM-I11 as a state in which signs of hyperactivity are no longer present, but other signs such as attentional deficits and impulsivity have continued without remission.' The symptoms of inattention and impulsivity result in some impairment in social or occupational functioning. These individuals are restless, fidgety, and unable to concentrate on a task until completion. Although they appear to have a great deal of energy, it is often disorganized and unfocused. There may be inattention and distractability also. This group is at high risk for antisocial behavior and substance abuse as well. The traditional teaching about the treatment of ADHD is that control of behavior is achieved by the time of adolescence and medication can be discontinued then. This concept is undergoing intensive reevaluation, and psychiatrists are now beginning to prescribe psychostimulants for adolescents and adults with these symptoms. The results are

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The second hypothesis, revolving around a common underlying functional abnormality of the brain, is likewise unprovable at this time. This construct is unlikely, however, because there does not seem to be a unitary cause for either ADHD or learning disabilities. A wide variety of brain insults can cause either condition or both, and the majority of children have no direct evidence of brain injury. It would seem, a priori, that inability to maintain sustained attention on a task would interfere with learning and the ability to achieve academically. This has been demonstrated in children with learning disabilities involving mathematics; children who underachieved in this subject were characterized by both perceptual-motor and attention deficits."%hildren with learning disabilities show deficits on tests of selective attention. Performance was lower in children with ADHD and learning disabilities compared with those with learning disabilities only.:j7These studies suggest that the deficit in attention that is part of ADHD contributes to poor academic performance, but not that it is the sole factor. The inability to sustain selective attention and the impulsivity component of ADHD have been shown to produce errors of commission in continuous performance tests, which also may contribute to problems with learning." Children with ADHD and hyperactivity and those without hyperactivity make similar numbers of commission errors on testing, but the hyperactive group fails to improve with practice.:j8 Finally, both impulsivity and hyperactivity are disruptive in the classroom setting. More time may be spent in disciplining the child than in teaching him. A body of evidence also suggests that there are no specific cognitive deficits that separate ADHD and learning disabilities and that the continuous failure of the learning-disabled child secondarily leads to behavior problems and the symptoms characteristic of ADHD.35 Although the etiologic issues are unsettled, there are important implications for clinical practice and for the recommendations made to the child's school. Learning disabilities are most appropriately treated with educational interventions. Medication can be considered for treatment of ADHD if the symptoms are severe and not adequately controlled by behavioral methods. Despite the seeming reasonableness of the assumption that by improving the ability to sustain attention there will be improvement in academic performance, this is not always the case. Although the child's behavior is less disruptive, the learning disability remains. A potential negative effect is that the child may no longer be singled out as a classroom prob-

:3 9

not as striking as have been reported for children, and there is a need for further s t ~ d i e s . ~ ~ , ~ ~ 11.

SUMMARY 12.

ADHD refers to a combination of symptoms in the general areas of inattention, impulsivity, and hyperactivity. This condition becomes evident in the preschool years and affects males predominantly. The behavior is seen as being disruptive and unacceptable by parents and teachers, and the child is socially handicapped as a result. Treatment relies on behavioral techniques and medication, predominantly psychostimulants. ADHD is strongly associated with learning disabilities; the treatment of the learning disorder should be based on educational intervention, not drug therapy. Symptoms of ADHD may continue into adulthood, and recommendations for treatment of adults are being made with increasing frequency. The prognosis is best for children who do not have symptoms of a conduct disorder and who lose the symptoms of ADHD before adolescence. A superimposed conduct disorder and niaintenance of the symptoms of ADHD put the patient at high risk for antisocial behavior and substance abuse in adolescence and adulthood.

13. 14. 15.

16. 17.

18.

19.

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