Attention deficit disorders affect three to five percent of school-aged children (DSM-IV, American Psychiatric Association, 1994). The diagnosis of attention deficit hyperactivity disorder (ADHD) is relatively unambiguous. Typically, ADHD diagnosis is based on behavioral observations in which the individual must display a number of developmentally inappropriate symptoms of inattention and hyperactivity-impulsivity. These symptoms must be observed in early childhood, be present in two or more settings, and remain consistent for a minimum of six months.
Less clear is the etiology of ADHD. Originally conceived as a child disorder, it is now recognized that ADHD continues into adolescence and adulthood, suggesting a more permanent basis for the disorder (Brown & Borden, 1986; Lambert, Hartsough, Sassone, & Sandoval, 1987). In an effort to understand the source, investigators have attempted to identify common characteristics of children, adolescents, and adults with ADHD using both cross-sectional and longitudinal studies. In a review of longitudinal studies by Klein and Mannuzza (1991), it was suggested that previously diagnosed children had higher rates of antisocial personality disorder and substance use disorders. Barkley, Fischer, Edelbrock, and Smallish (1990) examined a sample of previously diagnosed children. After eight years, they found that the majority still met criteria for ADHD, with 59% of these also meeting criteria for oppositional defiant disorder (ODD) and/or conduct disorder (CD). It was also reported that the proband group had a higher rat e of academic problems, including suspension, drop out, expulsion, and having failed a grade.
Another common finding in many follow-up studies is the report that individuals with a childhood diagnosis of ADHD are more likely to have an antisocial personality disorder or a nonalcohol substance use disorder as compared to a control group (Biederman, 1998; Mannuzza, Klein, Bessler, Malloy, & LaPadula, 1993; Mannuzza, Klein, Bessler, & Malloy, 1998). These studies also report that the proband group completed less schooling and had significantly lower occupational rankings. Milberger et al. (1997) also found that ADHD probands had a high risk for future substance abuse. Follow-up studies have shown that individuals diagnosed with ADHD in childhood have problems during adolescence and adulthood.
Given the early onset and consistency of symptoms associated with ADHD, present research has focused on central nervous system (CNS) substrates of ADHD. The area of study that appears to be promising is the frontal lobes of the brain. Mattes (1980) was the first to relate frontal lobe dysfunction with attention deficit disorder (ADD). Mattes linked ADD symptoms with symptoms arising from frontal lobe lesions in animals and humans. He further suggested that individuals with ADD and those with frontal lobe damage exhibit similar deficiencies.
Since Mattes' study investigators have continued to examine a link between frontal lobe dysfunction and ADHD. The working hypothesis is that frontal lobe functioning is poorer in those with ADHD as compared to non-ADHD individuals. However, using standard neuropsy-chological test probes, the results have been inconsistent. For example, the Wisconsin Card Sorting Test (WCST) is commonly used to assess frontal lobe functioning. Using the WOST, a number of studies have found significant differences between ADHD and non-ADHD persons (Chelune, Ferguson, Koon, & Dickey, 1986; Gorenstein, Mammatto, & Sandy, 1989; Shue & Douglas, 1992). Other studies have found no differences on the WCST between ADHD groups and control groups (Carter et al., 1995; Grodzinsky & Diamond, 1992; Loge, Staton, & Beatty, 1990; McGee, Williams, Moffit, & Anderson, 1989). The contradictory results of the different studies may be due to the criteria used to define the groups, the measures that were used to assess frontal lobe functioning, co morbidity of the ADHD group, and the age of the participants. …