660 CHAPTER 14
that examined people whose symptoms arose after age 7 (but generally by age 12)
found that the symptoms were virtually identical to those of people with an earlier
onset of the disorder, which suggests that the age cutoff is not meaningful (Faraone
et al., 2006; McGough & Barkley, 2004).
Third, symptoms of hyperactivity may be different in females than in males:
Girls who have hyperactive symptoms may talk more than other girls or may be
more emotionally reactive, rather than hyperactive with their bodies (Quinn, 2005).
Some researchers propose that ADHD is underdiagnosed in girls, who are less
likely to have behavioral problems at school and so are less likely to be referred
for evaluation (Quinn, 2005). In fact, female teenagers with ADHD are likely to be
diagnosed with and treated for depression before the ADHD is diagnosed (Harris
International, 2002, cited in Quinn, 2005).
Teachers are often the ones who fi rst raise the possibility that a particular child
has ADHD, and they are more likely to refer for evaluation children who disrupt the
class (hyperactive/impulsive type). One study found that teachers were more likely to
identify students as having ADHD when their class size was larger, and non-Hispanic
white children were more likely to be identifi ed than were Hispanic children (Havey
et al., 2005). Other studies fi nd that white children are more often diagnosed—and
treated—than black children (Stevens, Harman, & Kelleher, 2005).
Before diagnosing ADHD, however, a mental health clinician should be sure
that any diffi culties in fi nishing tasks are a result of attentional problems, and not
an oppositional attitude or diffi culty in understanding the instructions. For instance,
it turns out that Pia Enriquez simply hadn’t been paying attention when her par-
ents reminded her of her chores or asked her to set the table. Pia’s “absent-minded
professor” demeanor masked that fact that she has diffi culty paying attention and
becomes bored easily (particularly in the classroom, where she quickly grasps the
underlying concepts in the material the teacher presents). When diagnosing adults
with ADHD, clinicians should seek corroboration from school records or family
members.Understanding Disorders of Disruptive Behavior
and Attention
Given the high comorbidity and symptom overlap among the three disorders—
conduct disorder, oppositional defi ant disorder, and ADHD—we’ll focus on the
disorder that is best understood, ADHD. Studies of factors related to oppositional
defi ant disorder and conduct disorder probably include participants who also have
ADHD, which makes it diffi cult to determine which factors are uniquely associated
with oppositional defi ant disorder and conduct disorder and notADHD.Neurological Factors
Research on ADHD has revealed that people who have this disorder have abnor-
mal brain structure and function, and also has begun to characterize the role that
neurotransmitters and genes have in these brain abnormalities. Unfortunately,
researchers are only beginning to consider the different possible types of the disorder
separately—and thus at present only a very coarse picture is beginning to emerge.ADHD and Brain Systems
As noted earlier, people with ADHD may have impaired executive function (Kiliç
et al., 2007; Stuss et al., 1994). In addition, children and adults with ADHD cannot
estimate time accurately, which affects their ability to plan and follow through on
commitments (Barkley et al., 2001; Kerns, McInerney, & Wilde, 2001; McInerney &
Kerns, 2003; Riccio et al., 2005). Such functions rely in part on the frontal lobes.
In fact, researchers have proposed that the behavioral problems that charac-
terize people with ADHD may arise, at least in part, from impaired frontal lobe
functioning. Two sorts of fi ndings that support this view focus on brain structure
and on brain function. Regarding brain structure, children and adolescents with this