It is recognized that the core symptoms of ADHD in childhood are inattention, lack of impulse control, and hyperactivity. To make this diagnosis, these symptoms must be present to a greater degree than that in the average child of the same age and developmental level, begin early in life, be persistent over time, and be pervasive across settings. However, it is also well recognized that the core symptoms may be accompanied by symptoms of other disorders and may be accompanied by other comorbid, full-fledged medical, neurologic, and psychiatric disorders.
Essentially, all the conditions that are comorbid with ADHD can also mimic ADHD and be present in the differential diagnosis. The major comorbid disorders include psychiatric and developmental disorders such as poor peer relationships and social skills deficits, academic performance problems, communication disorders, other disruptive behavior disorders, substance abuse, mood disorders, anxiety disorders, tics and Tourette's syndrome, pervasive developmental disorders, and mental retardation. In addition, there are medical and neurological disorders that may be comorbid with as well as mimic the true ADHD syndrome.
Poor Peer Relationships and Social Skill Deficits
Children with ADHD have immature interactional skills, egocentric selfish behavior, poor awareness of and regard for the consequences of their own behavior, low frustration tolerance, increased sensitivity to environmental stimuli, and exaggerated emotional reactions. All of these may lead to rejection by the peer group. Some children with ADHD may be more avoidant in their inter-personal relationships than disruptive, and some present with schizoid or schizotypal characteristics.
Whatever the various types of difficulty, the general outcome is difficulty in making and keeping friends. Longitudinal studies show that strong peer relationships are a good predictor of adult mental health; thus, poor peer relationships are associated with a poor prognosis in children with ADHD.
Academic Performance Problems
Academic performance problems is a generic term to describe children not performing at the academic level that one would predict based on their chronologic age and their IQ. This term may also be ascribed to children who are doing grade-level work yet are very intelligent and not engaging in a higher level of work as predicted. There may be many different causes of the academic performance problems seen across children with ADHD. Some cases may be a direct result of the core symptoms of ADHD; others may be attributed to various specific learning disabilities and motivational problems.
Communication Disorders
Communication disorders describe developmental speech and/or language disorders. These children have elevated rates of ADHD. It is also clear that children referred for psychiatric problems and given a diagnosis of ADHD have undiagnosed speech and language disorders in a number of cases, as high as 40% and 50% in some samples. The nature of this relationship is not well understood. It may be that the speech and language disorders lead to attentional problems in some particular way or that they are both due to some common underlying factor, such as some type of central nervous system (CNS) dysfunction.
The long-term outcome of children with speech and language disorders is fairly good for the disorders themselves. However, these children are highly likely to develop learning disorders as a residual outcome of their speech and language disorders. Thus, the presence of communication disorders is likely to lead in ADHD children, as it does in non-ADHD children, to the development of academic performance problems due to specific learning disabilities in the language-related areas. This probability must be taken into account in the design of treatment plans to alter long-term negative outcome.
Oppositional-Defiant Disorder and Conduct Disorder
These two disorders are the other disruptive behavior disorders described in the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV). It is clear that there is a large overlap between ADHD and these disruptive behavior disorders. The symptoms may include refusing to comply with commands from adults such as parents, teachers, and coaches; doing the opposite of what is expected; disrupting the play of others; being verbally or physically aggressive; being destructive, such as breaking objects that do not belong to the child; lying; stealing; being truant; and committing other forms of delinquent behavior as the child gets older. Oppositional-noncompliant behavior occurs early in the course of ADHD if it is going to occur at all. It may be a forerunner of a later diagnosis of conduct disorder and antisocial personality disorder as the child matures into adolescence and adult life. The presence of aggression and conduct symptomatology and of oppositional- noncompliant behavior is a predictor of negative outcome, primarily the development of antisocial spectrum disorders in later adult life among children with ADHD.
Substance Abuse
Follow-up studies suggest that children with ADHD who go untreated are at risk of developing substance abuse problems with alcohol and other drugs. Those children with ADHD whose symptoms persist into adolescence and adult life and who also develop conduct symptomatology are at greatest risk of developing substance abuse problems. The choice of agent that is abused may be at least partially or environmentally determined. Genetic factors may also play a role for a predisposition to the development of both alcohol and other forms of substance abuse. Some adolescents and adults may use substances as medication to self-treat their undiagnosed and untreated ADHD symptoms.
Aggressive treatment of any substance abuse disorders is necessary as part of the total package of treating the ADHD condition.
Mood Disorders
The relationship of ADHD to mood disorders is not clear at present. A number of studies have found high rates of major depressive disorder and dysthymic disorder in children who carry a diagnosis of ADHD. Other studies have found higher rates of bipolar illness in both children and adults with a diagnosis of ADHD and also in their families.
Some investigators suggest that a rather unique form of mood disturbance may develop in individuals with ADHD. This disturbance begins early in childhood with brief periods of ups and downs that are generally related to environmental circumstances. As the child moves into adolescence and adulthood, the up periods become less frequent and the down periods become more frequent and more prolonged. The clinical picture looks like one of chronic dysphoria and may be mistaken for dysthymic disorder.
Mood disturbance in adolescents with bipolar disorder may be manifested as irritability rather than euphoria. Thus, irritability combined with restlessness, rapid speech, decreased need for sleep, and decreased concentration may be mistaken for ADHD when it is truly a manifestation of bipolar illness. Cases of children with an early diagnosis of ADHD who later developed a clear-cut episode of bipolar illness, whereby ADHD and bipolar illness could occur together, have been reported.
Cyclothymic mood swings may be present in children with ADHD and may even become more common as these children develop into adolescents and adults. High rates of cyclothymia, dysthymia, major depressive disorder, and bipolar illness have been reported in adults whose ADHD had remained undiagnosed in childhood but was later diagnosed in adult life as being a lifelong problem.
Treatment of mood disturbance requires the use of skilled psychopharmacologic and psychosocial interventions. In some cases, CNS stimulants may improve the mood disturbance in ADHD individuals to a greater degree than more standard anti-depressants such as tricyclic antidepressants.
Anxiety Disorders
There are a variety of studies suggesting that anxiety disorders of all types occur at elevated rates in children, adolescents, and adults with a diagnosis of ADHD. One study suggests that the presence of generalized anxiety in children with ADHD may indicate a definite subgroup that does not respond well to psychostimulant medication.
Obsessive-compulsive disorder may be particularly common in those children with ADHD who also have Tourette's syndrome and the full range of anxiety disorders; avoidant behavior, social phobia, panic disorder, and other anxiety disorders may occur at elevated rates in children with ADHD and in close family members.
Tics and Tourette's Syndrome
Approximately 40-60% of cases of Tourette's syndrome are preceded by ADHD that persists over time. The ADHD symptoms usually come first; tics come later. In some cases, tics are not present until the ADHD individual is treated with stimulant medication. Stimulant medication may both precipitate and worsen tics that are already present. Children who present with both ADHD and chronic tics and/or Tourette's syndrome are difficult to treat. The likelihood of Tourette's syndrome persisting into adult life is strong, and the tics may necessitate separate treatment such as clonidine, haloperidol, or pimozide in addition to the stimulant treatment of the ADHD syndrome.
Pervasive Developmental Disorders and Mental Retardation
Those children with significant cognitive impairment such as mental retardation and those with a pervasive developmental disorder who also have high rates of mental retardation often have ADHD symptomatology. Some studies suggest that the ADHD symptomatology in these individuals may respond to standard stimulant medication. Others have raised caution about the nature of attentional deficit in these children, suggesting that the problem may actually be a fixed, narrow attention span that may worsen with stimulant medication, even though physicians may be tempted to render treatment with stimulants because the behavior seems to worsen without it. Some have suggested the use of alternative agents, such as fenfluramine, to treat ADHD symptoms in these individuals.
Medical and Neurological Disorders
Many medical and neurological disorders may mimic ADHD, and they also may coexist with ADHD. Hyperthyroidism, infectious diseases of the CNS, fetal alcohol syndrome, fetal alcohol effects, exposure to cocaine in utero, lead poisoning, and posttraumatic organic brain syndrome may be comorbid with ADHD and may mimic a true ADHD syndrome.
Prospective studies suggest the following: there is a subgroup of children with ADHD, probably around the range of 30%, who seem to have a developmental delay picture; that is, some time in young adult life they no longer meet the criteria for the diagnosis of ADHD and no longer benefit from ADHD treatment. A second subgroup, maybe as many as 40%, have a continual display type outcome; that is, they continue to manifest several major symptoms if not the full syndrome of ADHD throughout their life span; they are also complicated by other difficulties in the emotional, behavioral, and cognitive areas.
A smaller subgroup, again approximately 30%, may be considered to have a developmental delay type of outcome; that is, they present with continual ADHD symptoms but also show various serious forms of psychopathology, especially in the antisocial spectrum area, such as antisocial personality disorder and alcohol or other substance abuse.
Comorbidity most likely plays a role in this outcome. The strongest correlation with ADHD in children is the presence of oppositional-defiant disorder and conduct disorder. In later life, the correlation is with antisocial spectrum disorders. It can be readily seen that all the comorbid conditions discussed previously will have their own natural history. In some cases, the natural history is worsened by the presence of ADHD. For example, the pathway from oppositional- noncompliant behavior to more serious delinquent behavior seems to be hastened by the presence of ADHD in childhood. Likewise, the treatment of ADHD syndrome will affect the core symptoms of ADHD and may have secondary benefit on some of the non-ADHD symptomatology. For example, aggressive behavior in ADHD children may decrease with the treatment of ADHD symptoms by stimulant medication. In other cases, specific treatment plans--both psychopharma-cologic and psychosocial--are going to be necessary to treat the comorbid conditions and to mitigate against the negative outcome.
Bibliography
Barkley RA. Attention deficit hyperactivity disorder: a handbook for diagnosis and treatment. NewYork: Guilford Press, 1990.
Barkley R, et al. Effects of age on the mother-child interactions of hyperactive children. J Abnorm Child Psychol 1985;13:631-638.
Biederman J, et al. Comorbidity of attention deficit hyperactivity disorder with conduct, depressive, anxiety, and other disorders. Am J Psychiatry 1991;148:564-577.
Campbell SB, et al. Noncompliant behavior, overactivity, and family stress as predictors of negative maternal control with preschool children. Dev Psychopathol 1991;3:175-190.
Cunningham CE, et al. The interactions of normal and hyperactive children and their mothers in free play and structured tasks. Child Dev 1979;50:217-224.
DuPaul GJ, et al. Response of children of ADHD in methylphenidate: interaction with internalizing symptoms. J Am Acad Child Adolesc Psychiatry 1994;33:894-903.
Hinshaw SP. On the distinction between attentional deficit hyperactivity and conduct problems in children with aggressive psychopathology. Psychol Bull 1987;101:443-463.
Hinshaw SP. Stimulant medication and the treatment of aggression in children with attentional deficit. J Clin Child Psychol 1991;20:301-312.
Jensen PS, et al. Anxiety and depressive disorders in attention deficit disorder with hyperactivity: new findings. Am J Psychiatry 1993; 150:1203-1209.
Mannuzza S, et al. Adult outcome of hyperactive boys: educational achievement, occupational rank, and psychiatric status. Arch Gen Psychiatry 1990;50:565-576.
Pelham WE, et al. Peer relationships in hyperactive children: description and treatment. In: Gadow K, Bailer I, eds. Advances in learning and behavioral disabilities. Greenwich, Conn: JAI Press, 1982:365-436.
Pelham WE, et al. Teacher ratings of DSM-III-R symptoms for the disruptive behavior disorders. J Am Acad Child Adolesc Psychiatry 1992; 31:210-218.
Reiff MI, et al. Children who have attentional disorders: diagnosis and evaluation. Pediatr Rev 1993;12:455-465.
Shaywitz SE, et al. Attention deficit disorder: current perspectives. In: Kavanaugh JF, Truss TJ, eds. Learning disabilities: proceedings of the national conference. Parkton, Md: York Press, 1988:369-523.
Swanson JM, et al. Effects of stimulant medication on learning in children with ADHD. J Learn Disabil 1991;4:219-230,255.
Wilens TE, et al. The stimulants. Psychiatr Clin North Am 1992;15:191-222.
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