Attention deficit hyperactivity disorder (ADHD) is characterized by inattention, hyperactivity, impulsivity, and cognitive, behavioral, and emotional deficits. ADHD is also closely related to learning disabilities, lack of self-control, and social skill deficits (Morris & Collier, 1987). About 7.6% to 9.5% of Korean children are reported to have ADHD (Cho & Shin, 1994; Kim & Chae, 1998).
Approximately half of ADHD children show overt symptoms by the time they are 5 years old, and most begin to display behavioral problems during the early school years when they have to follow instructions from teachers and obey school rules. ADHD children are reported to have difficulty with self-control both at home and in school, to have a tendency to show aggressive behaviors, to suffer from low self-esteem, to have frequent fights with peers, to experience isolation in social situations, to display problems with underachievement, and to have learning disabilities (Silver, 1992).
Longitudinal studies on ADHD indicate that hyperactivity and impulsivity decrease during adolescence (Hart, Lahey, Loeber, Applegate, & Frick, 1995). However, about 70% to 80% of ADHD children carry the major symptoms of ADHD into their adolescent years (Barkley, Fischer, Edelbrock, & Smallish, 1990; Barkley, Anastopoulos, Guevremont, & Fletcher, 1991), and about 50% to 70% of ADHD children are likely to suffer from residual ADHD during adulthood (Weiss & Hechtman, 1993; Wenwei, 1996).
Because ADHD children tend to have risk factors in cognitive, academic, and medical areas, there is likely to be comorbidity with other disorders. Barkley (1998) states that about half suffer from additional liabilities, and it is estimated that 30% to 50% of ADKD outpatients and 40% to 70% of ADHD inpatients experience other psychiatric disorders.
According to Barkley (1998), the comorbidity rate of ADHD with oppositional defiant disorder (ODD) is 20% to 67%, 20% to 56% for conduct disorder (CD), 10% to 40% for anxiety disorder, and 9% to 32% for depression. ADHD children who have additional psychological problems are likely to have trouble with peers and to be avoided by them; they tend to be aggressive toward other children and act in a noncompliant manner at home. Biederman, Newcorn, and Sprich (1991) also noted that ADHD children tend to suffer from CD, depression, learning disabilities, and borderline personality disorder, and to display disruptive behaviors.
Hong, Kim, Shin, and An (1996) indicated that 48.8% of ADHD children have comorbid conditions, and that Korean ADHD inpatients experience an average of 2.7 additional disorders. They reported the following frequencies for those comorbid conditions: specific developmental disorders, 11.6%; CD, 9.3%; ODD, 7%; anxiety, 7%; enuresis, 4.7%; and mental retardation, 4.7%. Kim (1996) reported that 23% of ADHD children suffer from ODD, 16% experience extreme anxiety, and 8% suffer from CD. Other studies have found that about half of ADHD children have ODD or CD, while approximately a quarter have both.
Children with ADHD and CD often have problems dealing with family conflicts, as well as an unhappy social life due to deficits in social skills and cognitive inhibition (Barkley et al., 1991; Jensen, Martine, & Cantwell, 1997). In a longitudional study by Satterfield et al. (1982), it was found that 50% of a sample of 110 ADHD children committed theft, robbery, and physical assault, and 19% were incarcerated, while only 10% of 88 non-ADHD children committed crimes, with none being incarcerated.
On the other hand, there is not much research on the comorbidity of ADHD with youths who have CD. In one recent study, 23% of Korean adolescents with CD were also identified as having ADHD (Lee, Oh, Lim, Chung, & Cho, 1998), but most of the CD adolescents were selected from school settings with no parental and teacher's behavioral reports available for identifying ADHD. …