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Association Between Attention Deficit-Hyperactivity Disorder and Learning Disorders Dennis P. Cantwell and Lorian Baker J Learn Disabil 1991 24: 88 DOI: 10.1177/002221949102400205 The online version of this article can be found at: http://ldx.sagepub.com/content/24/2/88

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disorder, terms such as hyperactivity and hyperkinesis became popular. Later, the cognitive studies of Douglas (1972, 1976, 1980) led to the widely accepted view of the disorder as being primarily a deficit in attention and concentration abilities. As a result, DSM-III (the American PsyDennis P. Cantwell and Lorian Baker chiatric Association's diagnostic nomenclature published in 1980) coined the term attention deficit disorder with hyperThis article discusses the relationship between attention deficit-hyperactivity disorder activity (ADDH). (ADHD) and learning disability (LD). The relevant literature is outlined, and em-Much of the work dealing with ADHD pirical data are presented from a prospective follow-up study of 600 speech/languageused rather vague descriptions of the disimpaired children. The data show an increased prevalence of both LD and ADHD order. For example, in Barkley's (1982) among children with early speech/language impairments. Furthermore, LD was review of 20 years of scientific papers on strongly associated with ADHD in both the initial and follow-up samples. Also,the syndrome, he found that the majority the children with LD had increased rates of other psychiatric disorders (e.g., behavior of works provided no diagnostic criteria. disorders, mood disorders, anxiety disorders). The implications of these data are Thus, most authors used nothing more discussed with regard to the possible etiology of the ADHD-LD association, treatthan their own opinions as the means of ment for children with LD and ADHD, and promising hypotheses for future determining whether the syndrome was research. present. As a result, it is likely that many early studies in the literature include his article discusses the association 5. What are the treatment implications children with a variety of different probbetween attention deficit-hyperof the answers to the above four lems under the diagnostic rubrics of MBD, hyperactivity, or ADDH. activity disorder (ADHD) and learning questions? disability (LD). There are difficulties DSM-III was a landmark in official Before examining the research litera- diagnostic nomenclature. In contrast to with the definitional boundaries of all of these terms, as is illustrated below. None- ture, some discussion of definitional prob- its predecessors (including DSM-I, DSMtheless, the recent research literature (in- lems will be provided, because general- II, and the various editions of the Intercluding our own studies of children with izations across studies are valid only national Classification of Diseases), it speech/language disabilities) suggests when the studies use comparable defini- provided detailed descriptions and specific diagnostic criteria for each disorder. that there may be some type of associa- tions and diagnostic criteria. The DSM-III definition of ADDH contion between the two problems. The pressisted of three major criteria: The first ent article briefly reviews that literature and presents several competing hypoth- DEFINITIONAL ISSUES: ADHD specified multidimensional symptoms (requiring symptoms in the dimensions eses regarding the possibility of an asADHD refers to a syndrome involving of inattention, impulsivity, and motor sociation. Five specific questions are symptoms such as attentional impairments, hyperactivity). The second specified an addressed: impulsivity, and motor overactivity. age of onset (prior to 7 years); and the 1. Is ADHD associated with LD to a Throughout the years, a number of terms third required a duration (of at least 6 degree greater than that predicted by have been used for this syndrome: The months). earliest works referred to a Brain Damchange? Although the DSM-III criteria were 2. Is such an association specific between age Behavior syndrome (Cantwell, 1986); specific in that they outlined particular LD and ADHD, or is it instead an but the failure to demonstrate "true brain requisite symptoms, they were not operaassociation between LD and disrup- damage" resulted in the later use of terms tional in the true sense of the word, tive behavior disorders in general? such as minimal brain damage and min- because they did not spell out a diag(The class of Disruptive Behavior Dis- imal brain dysfunction (MBD). These nostic process to determine the presence orders includes not only ADHD, but early approaches were etiological rather of those symptoms. Loney (1983) and also conduct disorder and opposi- than descriptive, in that they implied that Barkley (1982) provided examples of how some form of brain damage or central the diagnostic criteria for ADDH may be tional defiant disorder.) 3. Is there an association between LD nervous system dysfunction was respon- operationalized. Loney's (1983) work, and other types of psychiatric dis- sible for the behavioral symptoms. for example, used various mathematical orders (especially the "Emotional" or Later approaches moved away from and statistical procedures to determine "Internalizing" disorders)? etiologically based terminology, focusing the combinations of specific categorical 4. How might (i.e., through what me- instead on behavioral descriptions. In- and dimensional criteria that resulted in chanisms) ADHD and LD have come sofar as motor overactivity was first the greatest reliability. to be associated? viewed as the primary symptom of the The most recent of the behaviorally

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oriented terms is ADHD. This term is coined for DSM-III-R, the 1987 version of DSM-III. Whereas the DSM-III category of ADDH was a multidimensional monothetic category (that is, it required certain symptoms in three specific areas), the DSM-III-R category of ADHD was a unidimensional polythetic category that did not require any specific symptom or set of symptoms. Instead, DMS-III-R allowed any 8 symptoms to be selected from a set of a possible 14. The duration and age of onset criteria in DSMIII-R remained the same as in DSM-III. Since polythetic categories tend to be broader than monothetic categories, it is likely that there will be more children meeting the DSM-III-R criteria for ADHD than there were for the DSM-III category ADDH. Nonetheless, there is likely to be substantial overlap among the patients specified by these two DSM definitions.

DEFINITIONAL ISSUES: LD The definition of LD is even more problematic. Various terms have been used, including academic performance problems, academic underachievement, academic retardation, academic backwardness, educational backwardness, learning disorders, learning disabilities, MBD, perceptual handicap, reading retardation, and dyslexia. These terms have been used to represent different types of problems, although they are sometimes used interchangeably. In order to distinguish LD from poor academic performance that is the result of a child being younger than his or her peers, or having mild intellectual retardation, age and IQ must be taken into account. Academic retardation and educational underachievement are two terms that have been used to refer to children who perform academically below the levels expected from their age and IQ. As noted by Rutter (1974), however, it is not simple to determine the "expected levels" of a child's performance or to define what constitutes being "significantly below" those levels. One of the better methods (Rutter, Tizard, & Whitmore, 1970) calculates expected performance from a regression equation based on correlations in the general population be-

tween educational performance, chronological age, and intelligence level. Then, a cut-off for academic underachievement is set at a level that is relatively infrequent in the general population. Theoretically, this selects those children likely to have the poorest prognoses. Nonetheless, much of the learning research, especially that dealing with psychiatric aspects, has used methods that are less valid (such as achievement ratios, discrepancies between mental age and achievement age, or discrepancies between achievement age and chronological age). Another problem has to do with more subtle, theoretical distinctions, such as the difference between learning disability, learning deficit, and learning disorder. As pointed out elsewhere (Cantwell, 1986), ability is a term best used to describe an underlying, often inferred capacity, whereas performance is best used to describe observable and quantifiable behavior. Deficit is best used to describe something that is less than expected; and, finally, disorder is best used to describe a recurring pattern causing some degree of distress, disadvantage, or dysfunction. Thus, an observed, lower than normal performance in one aspect of learning (i.e., reading) measured by a standardized test is a performance deficit. The disability or disabilities that may have led to it cannot be observed, but rather are inferred. However, these distinctions in terminology are not maintained in most of the literature. The DSM-III and DSM-III-R definitions of specific reading disorder require performance on a standardized, individually administered test of reading skill that is significantly below the expected level, given the individual's schooling, chronological age, and mental age. Because there is no mention of underlying inferred capacities, these definitions are of learning disorder, not learning disability. The definitions may be inconsistently applied because they do not specify either the degree of performance deficit or the operational procedures for determining the deficit. The most common definition of learning disabilities was developed in 1967 by the National Advisory Committee on Handicapped Children, and later became the basis for the federal definition found in U.S. Public Law 94-142 (the Educa-

tion for All Handicapped Children Act of 1975). That definition is as follows: "Specific learning disability". . . means . . . a disorder in one or more of the basic psychological processes involved in understanding or in using language, spoken or written, which disorder may manifest itself in an imperfect ability to listen, think, speak, read, write, spell, or to do mathematical calculations. {Federal Register, 1977, p. 64) Such conditions as perceptual handicaps, brain injury, minimal brain dysfunction, dyslexia, and developmental aphasia are included in the definition, but learning problems that are primarily the result of visual, hearing, or motor handicaps; mental retardation; emotional disturbance; or environmental, cultural, or economic disadvantage are excluded (Federal Register, 1977, Section 121A5[9]). Although widely used, the above definition has difficulties that have been noted by various authors (Barkley, 1981; Hammill, Leigh, McNutt, & Larsen, 1987; Interagency Committee on Learning Disabilities (ICLD), 1987; Share, Richardson, & Bialer, 1980). Like the DSM definitions, it does not specify how far behind a child must be. Furthermore, the focus on underlying psychological processes is problematic, because we do not know what those processes are (Butler, 1984), nor is it clear how they can be measured. Furthermore, it is not clear how the exclusions are to be made, particularly since the inclusionary and exclusionary conditions may overlap with LD and with each other, intertwined in such a way that it becomes impossible to disentangle the direction of effect. Partly as a result of these difficulties, the National Joint Committee on Learning Disabilities revised the definition in 1981 (Hammill et al., 1987; Interagency Committee on Learning Disabilities, 1987). The revised definition reads: Learning disabilities is a generic term that refers to a heterogeneous group of disorders manifested by significant difficulties in the acquisition and use of listening, speaking, reading, writing, reasoning, or mathematical abilities. These disorders are intrinsic to the individual and presumed to be due to central nervous system dysfunction. Even though a learning disability may occur concomitantly with other handicapping conditions (e.g., sensory impairment, mental retardation, social and emotional disturbance) or environmental

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influences (e.g., cultural differences, insufficient or appropriate instruction, psychogenic factors), it is not the direct result of those conditions or influences. (ICLD, 1987, p. 221) Although this definition has been considered to be a substantial improvement over the P.L. 94-142 definition, it nevertheless has problems similar to those outlined above. Unfortunately, those problems are also still present in the most recent definition proposed by the Interagency Committee on Learning Disabilities (1987). This latest definition amended the 1981 definition by (a) expanding the list of manifestations to include difficulties in the acquisition and use of social skills and (b) expanding the list of handicaps that may occur concomitantly to include attention deficit disorder. Clearly there are many definitional issues that have not been resolved and that are central both to the delivery of clinical services and to research. Our present understanding of the association between ADHD and LD is hampered by differences across studies in the definitions, the inclusionary and exclusionary criteria, and the operational diagnostic procedures.

ASSOCIATION OF ADHD ANDLD An early study (Cantwell & Satterfield, 1978) found a high prevalence of academic performance problems in boys with ADHD as compared to age-matched boys with similar IQs who did not have attention problems. In that study, ADHD was diagnosed using behavioral criteria similar to those eventually published in DSMIII-R, and expected achievement levels were established using a regression equation based on age and Performance IQ (PIQ). More than one third of the ADHD boys were found to be at least 1 year below their expected levels in two of the academic subjects tested (i.e., reading, spelling, or mathematics). As well as being behind in more academic subjects, the children with ADHD were also more behind in the individual subjects. Similar findings have been reported in the literature in both cross-sectional (Anderson, Williams, McGee, & Silva, 1987; Holborow & Berry, 1986; Lambert & Sandoval, 1980) and longitudinal

(Charles & Schain, 1981; Huessy & Cohen, 1976) studies of children with hyperactivity. Follow-up studies of children with hyperactivity typically report that these children are destined for school failure, learning problems, and/or LD. For example, in Huessy and Cohen's (1976) follow-up study, half of the sample had experienced school failure by the time they reached ninth grade. Lambert and Sandoval (1980) examined underachievement (defined as a discrepancy between actual and IQ/age-appropriate achievement) in boys with and without hyperactivity. They found that 53% of the boys with hyperactivity (versus only 11% of the controls) were underachieving in either reading or math. In another follow-up study, Charles and Schain (1981) reported that the majority of preschoolers with hyperactivity functioned below grade-level expectations in reading and math, once they were in school. Furthermore, an association between learning difficulties and hyperactivity has been reported in several epidemiological studies. For example, Holborow and Berry (1986) used teacher questionnaires to determine the presence of hyperactivity and learning problems in a large epidemiological sample of elementary school children. They found that 27% of the children with hyperactivity also had learning difficulties. More recently, Anderson et al. (1987) reported that 80% of 11year-olds with ADDH (per DSM-III criteria) had learning difficulties (being at least 2 years behind) in reading, spelling, mathematics, or written language. Thus, although each of these studies has used slightly different definitions of ADHD and learning difficulties, they all support the hypothesis that academic difficulties and school failure are likely to be found in children with ADHD. This in turn suggests an association between LD and ADHD. Below, the nature of such an association is explored in more detail.

SPECIFICITY OF THE ASSOCIATION BETWEEN LD AND ADHD DSM-III-R groups ADHD, along with conduct disorder and oppositional disorder, into a general category of psychi-

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atric disorders called "disruptive behavior disorders." Other psychiatric classification systems have also grouped these disorders under the name "externalizing disorders" (Achenbach, 1985). Such grouping raises the question of whether the association of LD is with only ADHD, or whether LD is also associated with disruptive behavior disorders in general. Rutter (1974) suggested that specific reading retardation is one type of learning problem that is associated with behavior disorders in general. Rutter's seminal epidemiologic study on the Isle of Wight (Rutter et al., 1970) found that approximately one third of the children with conduct disorder also had specific reading retardation, and, conversely, one third of the children with reading retardation also had conduct disorder. Although the diagnosis of ADHD was not used in this study, the children in the concurrent disorders group were characterized by symptoms suggestive of the ADHD syndrome. There is also a substantial literature suggesting that children with conduct disorders, delinquency, or antisocial behavior have high rates of learning difficulties (Baker & Cantwell, in press; Hunt & Cohen, 1984; Lewis, Shanok, Balla, & Bard, 1980; Meltzer, Roditi, & Fenton, 1986; Zinkus & Gottlieb, 1978). Studies of delinquent children and adolescents reveal that reading disability in particular is very common. Thus, it would seem that other disruptive behavior disorders are also associated with LD. In Rutter et al.'s (1970) epidemiological study, the researchers compared three subgroups of children: those with pure conduct disorder, those with pure specific reading retardation, and those with concurrent conduct disorder plus specific reading retardation. It was found that the children with concurrent disorders most strongly resembled those with pure specific reading retardation. From this, the researchers concluded that the conduct disorder may have arisen in the children with concurrent disorders as a consequence of experiences with school failure. Other research studies support that conclusion for at least a subgroup of children who have both LD and conduct disorder. Studies examining the natural history of LD in delinquent children report that the onset of LD precedes deJournal of Learning Disabilities

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linquent behaviors about half the time (Offord, Poushinsky, & Sullivan, 1978). Furthermore, there is evidence of various subtypes of delinquency, only one of which is associated with LD (Meltzer et al., 1986). Our own work has examined the prevalence and types of psychiatric disorders and learning disorders found in children with speech and language impairments (SLI). These children constitute a particularly relevant sample because they are at risk for both psychiatric and learning problems (Baker & Cantwell, in press; Cantwell & Baker, 1987a). Our initial sample consisted of 600 SLI children, 69% male, ranging in age from 1 to 16 years, with a mean age of 5.6 years. Three hundred of these children were followed up 4 to 5 years later (at a mean age of 9.1 years). These studies are described in more detail elsewhere (Baker & Cantwell, 1987; Cantwell & Baker, 1985, 1987b). Psychiatric diagnoses using DSM-III diagnostic criteria revealed that initially 50% of the 600 children had a psychiatric illness. ADDH was by far the most common diagnosis, occurring in 19% of the children. However, oppositional and/or conduct disorders were found in an additional 7% of the group, making a total of 26% of the children who had some type of disruptive behavior disorder. Forty-two children in the initial sample had LD (see Note). Although this was a small proportion (7%) of the entire sample, it nonetheless represented a considerable proportion (more than 25%) of the children who were school aged. Behavioral and emotional problems were very common in the children with LD: 74% were diagnosed as having some type of psychiatric illness (as opposed to 50% in the total sample). For the children who had LD, the most common psychiatric diagnosis was ADDH. Forty percent had ADDH, and another 9% had either oppositional disorder or conduct disorder. Thus, a total of 49% of the children with LD also had a concurrent disruptive behavior disorder. Hence, although disruptive behavior disorder in general and ADDH in particular are common in SLI children in general, they are even more common in speech and language disordered children with LD. Four to five years later, 60% of the

300 children followed were found to be psychiatrically ill. Again, ADDH was the most common diagnosis, occurring in 37% of the follow-up sample. Another 8% had a diagnosis of either oppositional or conduct disorder, making a total of 45% with some type of disruptive behavior disorder. At follow-up, 91 of the 300 children had LD. Seventy-nine percent of these had some psychiatric diagnosis (compared to only 60% of the total sample). Again, ADDH was by far the most common diagnosis, present in 53% of the LD subsample. Another 5% of the children with LD had either oppositional or conduct disorder. Thus, at follow-up, the disruptive behavior disorders, and in particular ADDH, were again strongly associated with the diagnosis of LD. From the initial sample of 600 children, subsamples were drawn with and without LD, matched for chronological age and Performance IQ levels. Comparisons of these two subsamples again revealed a striking association between LD and behavior disorder. Psychiatric illness was present in 84% of the children with LD, versus only 49% of their matched controls. Sixty-eight percent of the children with LD had a behavior disorder, versus only 40% of the control children. These comparisons are both significantly different at the .0001 level. Furthermore, 45% of the children with LD had a diagnosis of pure behavioral disorder, as opposed to only 30% of the matched control group. This was significant at the .03 level. This analysis again suggests a strong association between psychiatric disorder and LD, and, in particular, between the disruptive behavior disorders and LD. When specific types of behavioral diagnoses were considered, again ADDH was by far the most common diagnosis. It was present in 63% of the children with LD, but in only 30% of the children in the matched comparison group. This difference was significant at the .0001 level.

ASSOCIATION OF LD WITH EMOTIONAL DISORDERS Emotional disorders are characterized by problems such as anxiety, depression, or mood disturbance. Rutter (1974) sug-

gested that, while there is some tendency toward an increased rate of emotional disorders in children with LD, the strongest association to LD is from behavior disorders. However, other authors have suggested that depression and anxiety may also be associated with LD. Several authors (Hunt & Cohen, 1984; Petti, 1978; Poznanski, 1982; Weinberg, Rutman, & Sullivan, 1973) have pointed out that problems in school performance and decreased concentration abilities are core symptoms of the depressive syndrome in children. Weinberg and Rehmet (1983) described an association between learning problems, depression, and hyperactivity in children attending a special school for learning disabilities. However, there have been no systematic studies examining either the prevalence of LD in depressed children or the prevalence of depression in LD children. Similarly, there have been no systematic studies examining either the prevalence of LD in children with anxiety disorders or the prevalence of anxiety symptoms or disorders in children with LD. Nonetheless, Hunt and Cohen (1984) suggested that anxiety disordered children may be at risk for the development of learning problems. Two theoretical mechanisms for such a risk are (a) the impaired attention, perception, memory, or abstraction that may occur in the highly aroused anxious state and (b) absence from school that may be a response to the child's anxiety. In our sample of 600 children with speech and language disorders, emotional disorders were also found to be relatively common. In all, 14% of the children had an emotional disorder (4% with a mood disorder and 10% with an anxiety disorder). At follow-up, 18% of the children had some type of emotional disorder (4% with a mood disorder and 14% with an anxiety disorder). Mood disorders were more common in those children who had LD. Initially, 17% of the children with LD had a mood disorder diagnosis, while only 2% had 2m anxiety disorder diagnosis. At follow-up, emotional disorder was present among 35% of the children with LD. The children with LD had a slightly lower rate (10%) of mood disorder, but a much higher rate (25%) of anxiety disorder. This indicates that the association of LD 91

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to the disruptive behavior disorders may not be as specific as some authors have suggested. Both anxiety and mood disorders may also be common in children with LD, at least among those with early speech and language difficulties. The comparison of the matched groups of children with and without LD again revealed elevated rates of emotional disorders associated with LD. Emotional disorders were present in 35% of the children with LD, versus only 17% of the children without LD. This difference was significant at the .001 level. The most prevalent emotional disorders were anxiety disorders; these were present in 24% of the children with LD and 11 % of the matched controls (a significant difference at the .001 level). The majority of children with LD did not have a, pure emotional disorder, however. In fact, 23% of the children with LD (versus 10% of the controls) had comorbid behavioral and emotional disorders. This difference was statistically significant at the .001 level. Hence, although our data show an association between emotional disorders and LD, they also show that emotional disorders, when present in children with LD, are likely to be accompanied by disruptive behavior disorders. This issue of co-morbidity is one that needs to be addressed in research studies. For example, the co-morbidity of behavior and emotional disorders may make it seem as though LD is associated with both diagnoses when, in reality, the association is being carried by only one of these diagnoses.

THE NATURE OF THE ASSOCIATION When two conditions, such as ADHD and LD, are found to be associated with each other, that association may be the result of various mechanisms. First, the ADHD may lead to the LD. Second, the LD may lead to the ADHD. Third, there may be common background factors that lead independently to ADHD and LD (in which case the association between ADHD and LD would be indirect). Intuitively, it seems likely that ADHD would lead to LD, in light of the core deficits of ADHD. That is, children who have difficulty with sustaining attention

over time or difficulty with selective attention would be expected to have academic performance problems. Likewise, children who have cognitive and behavioral impulsivity would be expected to have academic problems because they make decisions too rapidly or based upon inadequate data. Children who have fidgety, restless behavior also may not be able to put in enough time at a stretch in order to succeed academically. Although this explanation of the association between LD and ADHD makes intuitive sense, there is scant evidence that ADHD itself, as a diagnosis, leads directly to learning difficulties. In fact, there are many children who have the ADHD syndrome and do not have LD. As pointed out by McGee and Share (1988), longitudinal prospective follow-up studies are needed of preschool children with ADHD, concentrating on academic and cognitive factors. The continuity of preschool ADHD with grade-school ADHD, and their associations to the development of learning problems and LD, needs to be traced. Additionally, overlaps between ADHD and other problems, such as speech and language disorders and conduct disorder, need to be taken into account in order for a longitudinal study to be meaningful. It may be that these other associated problems, and not the ADHD itself, lead to the learning difficulties. Another type of useful study would compare children who have ADHD but do not have learning problems to children who have both ADHD and LD. One such study (Halperin, Gittelman, Klein, & Rudel, 1984) compared two groups of children who were hyperactive, one group with achievement scores average relative to their age and IQ, and another with reading disability relative to age and IQ. The study found minimal differences between the two groups in demographic, behavioral, or neuropsychological measures. Cunningham and Barkley (1978) were among the early investigators who proposed that the reverse mechanism of association might be true—that is, that problems with academic performance might lead to a clinical picture of ADHD in grade school. Again, the type of longitudinal studies necessary to establish this have not really been done. The work of

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McGee and colleagues (McGee, Share, Moffitt, Williams, & Silva, 1988; McGee, Share, Anderson, & Silva, 1986; McGee, Williams, Moffitt, & Anderson, 1989) suggests that children who have significant reading difficulties that persist over time are at increased risk for behavior problems. Although ADHD behaviors were common in the boys with LD in that study, conduct disorder symptoms and anxiety symptoms were also found. Hence, the association with LD was not specific to ADHD. The last possible mechanism of association—that LD and ADHD are related to each other because of common underlying factors—also seems intuitively plausible. Such underlying factors could be environmental, organic, or cognitive. Several studies have demonstrated, for example, that individuals with the ADDH syndrome tend to have less efficient cognitive styles (Cotugno, 1987; Douglas, 1972, 1976, 1980) and lower IQ scores (Ackerman, Anhalt, Dykman, & Holcomb, 1986). Furthermore, in a national probability sample of youngsters, below average attentiveness was found to be significantly associated with lower performance on tests of intelligence and achievement (Goldstein, 1987). However, considerable work is needed to clarify the nature of cognitive functioning and academic performance in children with ADHD, LD, and ADHD plus LD. Unfortunately, such work will necessarily be complicated by theoretical and measurement complexities. For example, the lower cognitive test scores that are obtained by a child with ADHD may not truly represent a learning disorder distinct from ADHD, but rather may be an artifact of the measurement process. The work of Douglas (1980) provides some insights into the nature of the cognitive functioning of children with ADHD and LD, and suggests that different types of cognitive disabilities may underlie the two disorders. In particular, Douglas's work indicates that children with ADHD have specific difficulties with the strategic problem-solving skills that are necessary for learning to occur. When children with ADHD were compared to nondisabled children on paired-associate learning tasks requiring the children to devise their own memory strategies, the children with ADHD did worse than their nonJournal of Learning Disabilities

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disabled peers. However, when these children were compared on a similar task involving pairs that were associated in a known and consistent way, the responses of the two groups were quite similar. Furthermore, the children with ADHD tended to do less well on memory tasks in a free recall situation, although they were not different from nondisabled students in a cued recall situation. If Douglas is correct, this would argue against the hypothesis that common underlying cognitive deficits lead to both LD and ADHD. On the other hand, McGee and Share (1988) pointed out that there are many pitfalls in the research on cognition that compares children with ADHD or LD. For example, they cite the Ackerman studies (Ackerman, Anhalt, Dykman, & Holcomb, 1986; Ackerman, Holcomb, & Dykman, 1986) that purported to demonstrate differences between non-ADHD LD children versus ADHD non-LD children in automatic and effortful processing. McGee and Share (1988) criticized those studies on the grounds of overlap in the diagnoses between the two groups. They also cited their own failure (McGee et al., 1988) to replicate the Felton study (Felton, Wood, Brown, Campbell, & Harter, 1987) demonstrating different underlying cognitive deficits in ADHD children versus children with LD. Thus, further investigation is needed comparing children with pure LD, children with pure ADHD, and children with both ADHD and LD. The definitions of LD reviewed at the beginning of this paper reflect the widely held belief that LD is intrinsic to the individual and most likely due to some type of central nervous system dysfunction. Our own work, reviewed above, suggests that speech and language disorders may in fact be a common background factor to both LD and psychiatric disorder, and in particular to ADHD. The data from our initial and follow-up studies of children with early speech and language difficulties lead to the following conclusions: 1. There is an increased prevalence of psychiatric disorders, of both the disruptive behavioral type and the emotional type, in children with speech and language disorders. Specifically, ADHD is quite common. However,

so are anxiety disorders. 2. There is an increased prevalence of learning disorders in children with speech and language disorder. 3. There seems to be a specific association between the presence of a psychiatric disorder and the presence of LD in SLI children. This specific association is strongest for the disruptive behavior disorders.

lant medication. Gittelman-Klein's (1987) review provides a good overview of the relevant studies. She points out that the Douglas study (Douglas, Barr, O'Neill, & Britton, 1986) was one of the few, if not the only, studies to investigate stimulant effect on academic performance using a research design free of methodological problems. Douglas found that methylphenidate produced significant improvement on both arithmetic and lanParticularly relevant to these conclu- guage task performance. Similarly, a sions is the recent work of August and 3-year multimodality study (Satterfield, Garfinkel (1989), who identified two sub- Cantwell, & Satterfield, 1979) combining types of ADHD, which they called "be- stimulants with various other forms of havioral" and "cognitive." In addition to intervention also found significant iminattention, impulsivity, and overactivity, provements in academic performance the cognitive subtype of the disorder was over time. However, there is no significharacterized by severe academic under- cant evidence to suggest that stimulants achievement and neuropsychological skill produce a positive effect on the academic deficits having to do with the encoding performance of children with LD who do and retrievel of linguistic information. not have associated ADHD. Such deficits are characteristic of childGittelman-Klein's (1987) review indicates hood language disorders and of reading that there has been very little research disabilities. These findings point to the comparing the cognitive and academic need for additional studies of cognition, effects of various combinations of stimespecially verbal/linguistic cognition, in ulant medications with other intervenchildren with ADHD and LD. tions. This is rather disappointing, because one would naturally assume that TREATMENT IMPLICATIONS the addition of another type of intervention specific to a particular parameter of Our own research and the other liter- dysfunction might additively improve the ature reviewed here indicate that ADHD outcome, as compared to stimulant mediand LD are associated to a much greater cation alone. degree than would occur by chance. McGee and Share's (1988) review notes However, the nature of this association that there have been studies focusing on remains unclear. The direction of effect the treatment of LD and accompanying (that is, LD leading to ADHD, ADHD classroom behavior problems. Most, if leading to LD, or some other mecha- not all, of those were very short-term nism) is important for treatment implica- studies employing small numbers of subtions. If ADHD leads to LD, then one jects whose psychiatric diagnoses were could postulate that treatment of the often questionable. More research is ADHD would lead to improvement in needed to determine the best treatment academic performance. If LD leads to approaches for all types of children with ADHD, concentration on the academic ADHD, children with LD, and children performance problems might be a pref- with ADHD/LD. erable treatment approach. In such a circumstance, successful treatment of the CONCLUSIONS learning problems might then result in the behavioral abnormalities improving This paper has not addressed some of secondarily. If there were common under- the issues that would be pertinent to a lying factors that led to both ADHD and definitive statement regarding the nature LD, then treatment directed at these of the relationship between ADHD and underlying factors should reasonably LD. Briefly, some key issues are the lead to improvement in both areas of possibility that there are subtypes of ADHD and/or subtypes of LD, and deficit. The treatment for children with ADHD there is an association only between certhat has been most investigated is stimu- tain of those subtypes. There is evidence

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from family studies, neurophysiologic studies, biochemical studies, and response to stimulant treatment studies that children with ADHD (diagnosed by whatever criteria) are not a homogeneous group. One possibility is that underlying components of attention may differentiate subgroups of ADHD children. The work of Anthony and his colleagues (Anthony, Mersky, Ahearn, Kellam, & Eaton, 1988) supports this hypothesis. These researchers used a neuropsychological battery involving four components of attention (focused, sustained, shift, and encoding) to determine the existence of distinctive attentional profiles that were associated with different teacher assessments of adaptive behavior, academic competence, and time-sampled observations of behavior. More work of this nature needs to be done. Clearly, attention is not a unitary phenomenon, and subtyping of attention along meaningful lines may help to clarify the interrelationship of certain types of attentional deficits with ADHD and LD. August and GarfinkePs (1989) identification of behavioral and cognitive subtypes of ADHD is another particularly promising neuropsychological study. The further delineation of the nature of underlying linguistic deficits that are present in children with ADHD and/or LD should do much to advance our understanding of both child development and psychopathology. The issue of the subtypes of LD has also not been addressed. Clearly, all children with reading disorder are not alike. Most likely, all forms of LD, be they reading, spelling, math, or some combination thereof, are of multifactorial etiology. As we have noted elsewhere (Baker & Cantwell, 1989), there is reason to believe that among phenomenologic and etiologic factors associated with LD, linguistic problems are probably the most important. However, there are some children with LD who have underlying visual-perceptual problems, and there probably are groups with various combinations of linguistic, visual-perceptual, memory, and attention problems. Ecologic and environmental variables may also be important for some children who suffered poor teaching or inadequate educational opportunities. Future research should concentrate on

subtypes of the population with ADHD and subtypes of the population with LD, in order to divine the degree and nature of the relationship between these two broad groups of disorders. A promising starting place would be with preschool children, especially those that can be identified as being at risk for both ADHD and LD. Our work with speech and language disordered children has shown them to be one such group. Following such children over time, and examining the continuing or discontinuing interrelationships between ADHD and LD, would hopefully help to clarify the relationship. Following preschool children with attentional difficulties would also be helpful.

Ackerman, P.T., Anhalt, J.M., Dykman, R.A., & Holcomb, P.J. (1986). Effortful processing in children with reading and/or attention disorders. Brain and Cognition, 5, 22-40. Ackerman, P.T., Holcomb, P.J, & Dykman, R. (1986). Presumably innate and acquired automatic processes in children with attention and/or reading disorders. Journal of Child Psychology and Psychiatry, 27, 513-529. American Psychiatric Association. (1980). Diagnostic and statistical manual of mental disorders (3rd ed.), Washington, DC: Author. Anderson, J.C., Williams, S., McGee, R., & Silva, P. A. (1987). DSM-III disorders in preadolescent children. Archives of General Psychiatry, 44, 69-76. Anthony, B.J., Mersky, A.F., Ahearn, M.B., Kellam, S.G., & Eaton, W. W. (1988, October). Structure of attention and epidemiology of its dysfunction in children. Paper presented at the annual meeting of the American Academy of Child and Adolescent Psychiatry, Seattle, Washington.

ABOUT THE A UTHORS

August, G.J., & Garfinkel, B.D. (1989). Behavioral and cognitive subtypes of ADHD. Journal of the American Academy of Child and Adolescent Psychiatry, 28, 739-748.

Dennis P. Cantwell is director of residency training in child psychiatry and Joseph Campbell Professor of Child Psychiatry at the UCLA School of Medicine and Neuropsychiatry Institute. He received his MD from the Washington University School of Medicine in St. Louis. His research interests include psychiatric diagnosis and classification, attention deficit-hyperactivity disorder, childhood depression, and developmental speech/language disorders. Lorian Baker holds a PhD in psycholinguistics from UCLA and is currently research professor in the Department of Child Psychiatry at the UCLA School of Medicine and Neuropsychiatry Institute. Her research centers upon speech/language development and disorders and their relevance to the field of child psychiatry. Address: Dennis P. Cantwell, UCLA Neuropsychiatric Institute, 760 Westwood Plaza, Los Angeles, CA 90024.

Baker, L., & Cantwell, D.P. (1987). A prospective psychiatric follow-up of children with speech/ language disorders. Journal of the American Academy of Child and Adolescent Psychiatry, 26, 546-553. Baker, L., & Cantwell, D.P. (1989). Specific language/learning disorders. In T.H. Ollendick & M. Hersen (Eds.), Handbook of child psychopathology (2nd ed., pp. 93-104). New York: Plenum Press. Baker, L., & Cantwell, D.P. (in press). The association between emotional behavioral disorders and learning disorders in children with speech/ language impairments. Advances in Learning and Behavior Disabilities.

Barkley, R.A. (1981). Learning disabilities. In E. Mash & L. Terdal (Eds.), Behavioral assessment of childhood disorders (pp. 441-482). New York: NOTE Guilford Press. For convenience, we use the term LD to describe Barkley, R. (1982). Guidelines for defining hyperactivity in children: Attention deficit disorder with these children, although we recognize that it is a hyperactivity. In B.E. Lahey & A.B. Kazdin poorly defined term. The P.L. 94-142 and ICLD (Eds.), Advances in clinical psychology (Vol. 5, definitions were not specifically used in our study, pp. 137-180). New York: Plenum Press. although they would nonetheless apply to these children. The study used DSM-III (American Psy- Butler, K. (1984). Language processing: Halfway chiatric Association, 1980) criteria for specific up the down staircase. In G. Wallach & K. Butler developmental learning disorder and operational (Eds.), Language learning disabilities in schoolcriteria requiring a statistically significant discrepanage children (pp. 60-81). Baltimore: Williams & Wilkins. cy between expected and actual academic achievement based on McLeod's (1978) formulae using Cantwell, D.P. (1986). Attention deficit and assononverbal Wechsler Intelligence Scale for Childrenciated childhood disorders. In T. Millon &G.L. Revised (WISC-R) (Wechsler, 1974) IQ, chronoKlerman (Eds.), Contemporary directions in psychopathology (pp. 403-428). New York: Guilford logical age, Wide Range Achievement Test (Jastak, Press. Bijou, & Jastak, 1976) scores, and Gray Oral Reading Test (Gray, 1967) scores. Cantwell, D.P, & Baker, L. (1985). Psychiatric and learning disorders in children with speech and language disorders: A descriptive analysis. Advances in Learning and Behavioral Disabilities, REFERENCES 4, 29-47. Achenbach, T. (1985). Assessment and taxonomy Cantwell, D.P., & Baker, L. (1987a). Developmenof child and adolescent psychopathology. Beverly tal speech and language disorders. New York: Hills: Sage. Guilford Press. Journal of Learning Disabilities

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problems, and juvenile delinquency. In D.H. Saklofske & S.B.G. Eysenck (Eds.), Individual differences in children and adolescents: International perspectives (pp. 158-172). London: Hodder and Stoughton. McGee, R., Williams, S., Moffitt, T.E., & Anderson, J. (1989). A comparison of boys with attention and/or reading disorders on neuropsychological measures. Journal of Abnormal Child Psychology, 17, 37-53. McLeod, J. (1978). Psychometric identification of children with learning disabilities. Institute of Child Guidance and Developmental Monograph. University of Saskatchewan. Meltzer, L.J., Roditi, B.N., & Fenton, T. (1986). Cognitive and learning profiles of delinquent and learning-disabled adolescents. Adolescence, 21, 581-591. Offord, D.R., Poushinsky, M.F., & Sullivan, D. (1978). School performance, IQ, and delinquency. British Journal of Criminology, 18, 110-127. Petti, T.A. (1978). Depression in hospitalized child psychiatry patients—Approaches to measuring depression. Journal of the American Academy of Child Psychiatry, 18, 49-59. Poznanski, E.O. (1982). The clinical phenomenology of childhood depression. Journal of Orthopsychiatry, 52, 303-313. Rutter, M. (1974). Emotional disorder and educational underachievement. Archives of Disease in Childhood, 49(4), 249-256. Rutter, M., Tizard J., & Whitmore, K. (Eds.). (1970). Education, health, and behaviour. London: Longman and Green. Satterfield, J.H., Cantwell, D.P., & Satterfield, B. T. (1979). Multimodality treatment: A two-year study of 61 hyperactive boys. Archives of General Psychiatry, 36, 915-919. Share, R.A., Richardson, E., & Bialer, I. (1980). Toward operationalizing a psychoeducational definition of learning disabilities. Journal of Abnormal Child Psychology, 8, 5-20. Weinberg, W., & Rehmet, A. (1983). Childhood affective disorder and school problems. In D.P. Cantwell & G.A. Carlson (Eds.), Affective disorders in childhood and adolescence—An update (pp. 109-128). New York: Spectrum. Weinberg, W.A., Rutman, J., & Sullivan, L. (1973). Depression in children referred to an educational diagnostic center. Journal of Pediatrics, 83, 1064-1072. Wechsler, D. (1974). Wechsler intelligence scale for children-Revised. New York: Psychological Corp. Zinkus, P. W., & Gottlieb, M.I. (1978). Learning disabilities and juvenile delinquency. Clinical Pediatrics, 17, 775-780.

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