The comorbidity of conduct disorder (CD) and attention-deficit hyperactivity disorder (ADHD) in children and adolescents: The developmental persistence into adult antisocial behavior disorders (ASBD)

Meredith Peiken
University of Georgia

The study of behavioral problems in children and adolescents has become an interesting topic of mental health professionals, school officials, and the community at large alike because of the severe social implications such disorders carry. The social impact of these disorders are enormous in terms of financial costs, familial stress, disruption in schools, and the potential for criminal acts and substance abuse (Biederman, Newcorn & Sprich, 1991). Such behaviors also cause distress for the child or adolescent. Many of these children are unhappy because of a lack of peer associations, and opportunities are missed due to academic and learning difficulties (Nelson & Israel, 1997).

Behavioral problems are not uncommon; they are the most common disorders in youth treated by the medical community. However, these disorders are not readily diagnosed because of the difficulty in discerning dysfunctional behaviors from mere immaturity and functional childhood actions. Assessments are based on childhood developmental norms and cultural norms defined by the society in which the child or adolescent resides (Nelson & Israel, 1997). Age of onset is important to note in determining the developmental norms because as the child matures, such behaviors may be abandoned. A common assumption of behavioral problems of children and adolescents is that they are pervasive and extend throughout development. However, predicting if such disorders lead to other psychological problems is debatable because of change (Nelson & Israel, 1997). Do disorders diagnosed early in life carry over throughout development and into adulthood, or do they change with maturity?

Comorbid disorders, or multiple disorders seen in one individual, are quite common with behavioral disorders in children and adolescents. Prevalence rates vary due to specific disorders, but they range from 10% to 50%. The two most common comorbid disorders among all behavioral dysfunctions are conduct disorder (CD) and attention-deficit hyperactivity disorder (ADHD). ADHD and CD have been found to co-exist in 30%-50% of the reported cases (Biederman, Newcorn, & Sprich, 1991). Research explaining why these two behavior disorders are highly comorbid are inconclusive because such disorders do vary along a continuum, and the developmental changes in children occur so rapidly, adequate sampling is difficult. Researchers also have not found evidence of why some children develop these comorbid disorders and others do not. Studies on the comorbidity of CD and ADHD are trying to determine whether these disorders are etiologically separate disorders randomly occurring together or if the symptoms of both disorders are part of a larger behavioral syndrome (Biederman, Newcorn, & Sprich, 1991). Several hypotheses have been proposed by Biederman and colleagues explaining such comorbid patterns: 1) comorbid disorders are a distinct subtype of the original disorder; 2) one syndrome is an early manifestation of the comorbid disorder; and 3) the development of one disorder increases the risk of development of the comorbid disorder (1991). With regards to CD and ADHD, these summarize as: 1) CD with ADHD and vice versa are distinct subtypes of the disorder first manifested; 2) ADHD is and early manifestation of CD; and 3) having ADHD increases the risk of further diagnosis of CD.

This paper will focus on conduct disorder and attention-deficit hyperactivity disorder in childhood and in adolescence and the implications later in development if these two behavioral disorders occur simultaneously.

Conduct disorder is defined to be a pervasive pattern of disregard for and violation of the rights of others occurring since the age of 10, during which some of the following symptoms are present. The individual has erratic temperament, argues with adults, breaks rules, blames others for his/her own misgivings, is vindictive, participates in physical fights, exhibits cruelty to animals, is destructive, and has frequent run-ins with the law (Hinshaw and Andersen, 1996). Other symptomatic behaviors include showing off, boisterousness, and running away (Kazdin, 1985). Excessive aggression is the most socially disruptive symptom of CD (Steiner & Wilson, 1999). Antisocial behaviors are synonymous to conduct disorder but do not necessarily fulfill DSM-IV criteria of antisocial behavior (Steiner & Wilson, 1999). Children and adolescents with conduct disorder are likely to suffer deficiencies in other areas than those used to define CD like poor academic skills and a lack of peer relations (Kazdin, 1985).

Diagnosis of CD takes two forms, childhood-onset and adolescent-onset. Childhood onset occurs prior to age 10, while adolescent-onset is diagnosed after the age of 10 (Steiner & Wilson, 1999). An impressive distinction between childhood-onset and adolescent-onset is how the aggression levels vary. Adolescent-onset, the more common developmental pathway, is less aggressive, has a lower risk of comorbid disorders, and a better prognosis with age because adolescent-onset is less likely to persist into adulthood due to maturity (Steiner & Wilson, 1999). Conduct disorders manifested at a later age are more likely due to life changes, delinquent peer pressures, and other environmental factors than family history of behavior disturbances, alcoholism, antisocial personality disorder (ASPD), and neuropsychiatry problems. As children, adolescents with newly diagnosed CD express little aggressive and antisocial behaviors. During adolescence, their behavior patterns are less generally severe and more covert like substance abuse and running away (Nelson & Israel, 1997). The earlier the age of onset of CD generally is correlated to more serious and persistent antisocial behaviors. Childhood-onset, also coined life-course persistent antisocial behavior, is marked by severe aggression, and those children diagnosed with CD prior to age 10 are twice as likely to progress to ASPD in adulthood (Steiner & Wilson, 1999). This developmental pathway of CD is less common; about 3%-5% of the general population are life-course persistent (Moffit, 1993). Many childhood-onset do not progress further into adolescents with CD and/or ASPD adults, but of those who do, more cases of comorbid disorders are seen as well as academic and learning disabilities (Hinshaw, Lahey, & Hart, 1993).

There seems to be a clear progression of developmental stages in CD, particularly childhood-onset. However, not all children go through the marked stages; some merely stay transfixed in one stage while others outgrow the disorder completely (Nelson & Israel, 1997). In this symptomatic progression, less severe behaviors precede the more serious behaviors, but the new more serious antisocial behaviors may or may not replace the old less serious ones (Nelson & Israel, 1997). Early childhood expression of CD is recalcitrant behaviors and demanding attention; middle childhood CD behaviors include cruelty to animals and people, lying, cheating, and destructive acts; adolescent CD is manifested by deliberate setting of fires, stealing, vandalism, and substance use and abuse (Kazdin, 1985). It is interesting to note that as the behaviors of the CD child increase in severity they also decrease in overtness and in frequency.

The prognosis of youth with CD varies significantly with age of onset, types of antisocial behaviors, and maturity levels. Nevertheless, Biederman, et al. (1991) and Kazdin (1995) have both found that there is a strong predictive power of CD with future psychiatric disorders, social maladjustment, marital discord, ASPD, alcoholism and other types of substance abuse, and criminality. Kazdin (1995) found that 40% of youth with CD do not progress to ASPD, albeit large minority, however prognosis of the other 60% is unknown. There is a definite relationship between ASPD and CD, although it is uncertain of how the two disorders interact except for the fact that in diagnosing ASPD, CD prior to age 15 is necessary (Routh & Dougherty, 1992). Antisocial behaviors in adulthood rarely emerges de novo; these individuals consistently have some history of childhood or adolescent antisocial behaviors (CD) which begin as mild behavioral disruptions but intensifies with age and continues throughout development (Kazdin, 1985). Antisocial personality disorder reflects change in symptoms of CD but there remains clear pervasive character pathology related to ASPD (Steiner & Wilson, 1999).

Another behavioral disorder similar to CD is attention-deficit hyperactivity disorder. ADHD is the most common emotional, behavioral, and cognitive disorder treated in children; it affects 2%-12% of the general population. This disorder is marked by impulsive behaviors, inattentiveness, distractibility, and hyperactivity in children and adolescents (Wilens, Biederman, & Spencer, 1999). Other symptoms include low frustration tolerance, frequent shifts in activity, easily bored, difficulty with organization, daydreaming, and possibly aggression. Behaviors of the ADHD child are bothersome, socially awkward, disruptive, non-compliant, and disagreeable (Nelson & Israel, 1997). The annoying behaviors may seem unintentional and may be altruistic, but they may also be means of manipulation by the child to obtain what he/she desires. These children have a high social impact; they are sociable and talkative. Their behaviors are pro-social but are mostly expressed out of social context prescribed by social norms (Nelson & Israel, 1997). These children are highly aggressive, both physically and verbally; peers rate ADHD children as troublesome and tend to dislike and reject them. Disruptive ADHD behaviors are the most problematic when under behavioral restraint (ex. at school), when under public scrutiny (ex. the grocery store). And when persistence in work-related tasks (ex. homework, chores, etc.), but these behaviors are less likely to be behavioral management problems when the child does not have to exhibit self-control (ex. free play) (Barkley, 1996).

The behaviors of ADHD often emerge prior to enrollment in formal schooling or after a short involvement in school because these disruptive behaviors are easily detected in the restrained environment of the classroom (Comer, 1998). Children with ADHD are referred to the medical community initially because of the possible learning and communication difficulties; many are first thought to be mentally retarded (Comer, 1998). The age of onset is usually prior to the age of 7, although some diagnoses have been made at a later age. The symptoms of ADHD are commonly separated into two main symptoms, disinhibition and inattentiveness. The problems with disinhibition are usually the first to arise, usually around the age of 4 years old, while the inattentiveness typically emerges around 5-7 years of age generally when children begin grammar school (Barkley, 1996). The symptoms of disinhibition tends to decline with age, possibly related to maturity, however, the inattentiveness of the ADHD child remain salient throughout grammar school (Barkley, 1996). If inattentiveness goes into remission, it is usually experience around puberty (age 12-14).

Attention-deficit hyperactivity disorder is sub-divided into three descriptive types: predominantly inattentive, predominantly hyperactive-impulsive, and a combination of the two (Comer, 1998). Wilens, Biederman, & Spencer (1996) have found that the inattentive subtype generally has a lower level of inattention, aggression, and later delinquency, thus, this children diagnosed with this subtype have fewer comorbid disorders than the other two subtypes but have a greater academic impairment. Predominantly inattentive ADHD is prevalent in 20%-30% of all ADHD diagnoses. The hyperactive-impulsive subtype is less common, occurring in less than 15% of all ADHD children. This subtype is typically less disruptive than the other two; majority of the behavior problems are seen at home rather than in public or school settings (Wilens, Biederman, & Spencer, 1996). The most common ADHD subtype is the combination of inattentiveness and hyperactive-impulsive. The rate of diagnosis is 50%-75% (Wilens, Biederman, & Spencer, 1996). Children with the combination subtype are marked with more aggressive and disruptive behaviors across all situations. They also have a higher risk of more psychiatric comorbidity (Wilens, Biederman, & Spencer, 1996). The behaviors of ADHD youth and the attitudes surrounding these children are very similar to those of CD youth. Almost 80% misbehave seriously in school, which is a result of their inability to concentrate. The expression of this frustration is acting-out to gain attention from the adult. Their impulsivity, inattentiveness, and constant movement creates problems using careful judgement and is noticed in rash decision making (Comer, 1998). These children are viewed as a possible threat to public health because they are at a greater risk for development of severe psychopathology including greater social and emotional difficulties (Biederman, Newcorn, & Sprich, 1991). Childhood ADHD is linked to antisocial behaviors in two main ways: 1) these children are more likely to exhibit antisocial behaviors in childhood and adolescents; and 2) ADHD youth have a poorer prognosis over time for those with comorbid CD (Stoff, Breiling, & Maser, 1997).

Twenty percent to 30% of all ADHD children meet criteria for CD, and the prevalence for CD rises with age of the ADHD child (Nelson & Israel, 1997). In correspondence to one of Biederman, et al.’s hypothesis of the comorbid CD with ADHD, some clinicians believe ADHD forecasts CD because the age of onset for ADHD is significantly younger than the age of onset for CD. Childhood-onset CD is more likely to have comorbid ADHD than a later onset of CD because behaviors of CD as defined by DSM-IV criteria must be persistent prior to age 10 (Nelson & Israel, 1997). Diagnosis of comorbid ADHD and CD are more prevalent in pre-pubertal children than adolescence; the co-occurrences of symptoms seem to diminish with age (Stoff, Breiling, & Maser, 1997). Children with ADHD and comorbid childhood-onset CD have a more serious clinical outcome than do ADHD patients without comorbid CD because the symptoms and outcomes seem to overlap quite significantly (Biederman, Newcorn, & Sprich, 1991).

Attention-deficit hyperactivity disorder is more related to cognitive impairments and neurodevelopment anomalies where as CD is strongly associated to adverse family factors and psychosocial development, thus ADHD children with comorbid CD are more likely to have persistent behavioral problems into adulthood (Nelson & Israel, 1997). Youth with only CD tended to have fathers who were substance abusers and mothers with depression, ASPD, and substance abuse problems, while youth with CD and comorbid ADHD were likely to have fathers with a strong history of aggression, criminality, and imprisonment (Routh & Dougherty, 1992). It seems that defiance, not hyperactivity is associated with impaired family relationships and adverse social factors.

There are strong implications that the degrees of persistence of antisocial behaviors depend on the presence or absence of hyperactivity (Stoff, Breiling, & Maser, 1997). Comorbid CD with ADHD is related to a poor prognosis of the child. These children are at a higher risk of developing substance abuse disorders, having persistent attention deficit problems into adolescence and adulthood, and poor interpersonal relations (Steiner & Wilson, 1996). These youth with comorbid CD and ADHD may define solutions to problems in aggressive ways, anticipate fewer negative consequences for their aggressive behaviors, and hold a belief system of aggression that supports its use (Nelson & Israel, 1997). They truly believe that aggression is a legitimate solution to interpersonal problems. For these children, aggression is rewarded by its outcomes; they increase their self-esteem through its use, they notice a reduction in adverse behaviors of others, and generally get what they desire through its use (Nelson & Israel, 1997). This also creates a cognitive distortion for these individuals. They think that aggression is a reasonable means to an end. Youth with comorbid CD and ADHD also interpret the intent of others as more aggressive if the true intent is somewhat ambiguous and will retaliate aggressively first. These children and adolescents do get into more fights at school than other none comorbid children (Nelson & Israel, 1997). Because of this lack of social and interpersonal skills, these children have a harder time with adjustment. Their peers rate them as less desirable friends because of their unsociable behaviors of hyperactivity, impulsivity, and aggression.

Treatments for such behavior disorders vary from psychopharmacology to psychotherapy, and the results are also variable. Adolescent-onset CD is more responsive to medications and therapy, but it is also common that these youth mature out of their disorder. Inattentive subtype of ADHD is also fairly responsive to therapy, such as stimulant drugs. However, the most common forms of comorbid CD and ADHD are childhood-onset and combination subtype ADHD. Therefore, treatment outcomes for this specific combination of disorders are grave; many clinicians hope the child will grow out of the disorder with development.

The causal factors of why these two disorders are comorbid remain unfounded. In a study conducted by Biederman, et al. (1991), symptoms of hyperactivity and aggression were not highly correlated suggesting separate etiological dimensions. Likewise, childhood ADHD without CD was correlated with cognitive and academic deficiencies. However, the presence of CD in childhood whether associated with ADHD or not was correlated with aggressive behaviors and delinquency in adolescence (Biederman, Newcorn, & Sprich, 1991). These findings do suggest a definite separation of the two disorders, yet they are highly comorbid. Research on this relationship is lacking but there is a special need to identify such antisocial behaviors in childhood because of the implications for identifying causes, preventive possibilities, and later intervention.

It is clear that CD and ADHD are both problematic disorders that occur in children and adolescents. These disorders affect not only the youth, but also people around the child. Negative labels like “problem-child,” delinquent, and sociopath are commonly associated with children and adolescents with either CD or ADHD because of the behaviors exhibited by the disorder. These children typically do not excel in school, have few friends, and lack social skills to function in public and as an adult. A child or adolescent with both CD and ADHD has more issues to deal with because the child is not only demanding and aggressive, but is also hyperactive and impulsive. The prognosis for someone like this is not positive. Their chances of remaining disruptive throughout development into adulthood increases. They still lack the social skills needed to survive in the adult world, and continue having problematic relations with other. Adults with behavioral issues are not liked; they tend to be the typical criminal or antisocial individual. Therefore, more research is needed on this topic to figure out why these two disorders occur together or occur at all, and try to find adequate treatment options to better the lives of these children and adolescents in hopes that they will not become the disruptive and menacing adults in today’s society.

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