Inadequate or variable self-application to tasks that require sustained effort is often in- terpreted by others as laziness, irresponsibility, or failure to cooperate. Family relation- ships may be characterized by discord and negative interactions. Peer relationships are often disrupted by peer rejection, neglect, or teasing of the individual with ADHD. On av- erage, individuals with ADHD obtain less schooling, have poorer vocational achievement, and have reduced intellectual scores than their peers, although there is great variability. In its severe form, the disorder is markedly impairing, affecting social, familial, and scholas- tic/occupational adjustment.
Academic deficits, school-related problems, and peer neglect tend to be most associ— ated with elevated symptoms of inattention, whereas peer rejection and, to a lesser extent, accidental injury are most salient with marked symptoms of hyperactivity or impulsivity.
Oppositional defiant disorder. Individuals with oppositional defiant disorder may re- sist work or school tasks that require self—application because they resist conforming to others' demands. Their behavior is characterized by negativity, hostility, and defiance.
These symptoms must be differentiated from aversion to school or mentally demanding tasks due to difficulty in sustaining mental effort, forgetting instructions, and impulsivity in individuals with ADHD. Complicating the differential diagnosis is the fact that some individuals with ADHD may develop secondary oppositional attitudes toward such tasks and devalue their importance.
Intermittent explosive disorder. ADHD and intermittent explosive disorder share high levels of impulsive behavior. However, individuals with intermittent explosive disorder show serious aggression toward others, which is not characteristic of ADHD, and they do not experience problems with sustaining attention as seen in ADHD. In addition, intermit- tent explosive disorder is rare in childhood. Intermittent explosive disorder may be diag- nosed in the presence of ADHD.
Other neurodevelopmental disorders. The increased motoric activity that may occur in
ADHD must be distinguished from the repetitive motor behavior that characterizes stereo- typic movement disorder and some cases of autism spectrum disorder. In stereotypic movement disorder, the motoric behavior is generally fixed and repetitive (e.g., body rock- ing, self—biting), whereas the fidgetiness and restlessness in ADHD are typically general- ized and not characterized by repetitive stereotypic movements. In Tourette’s disorder, frequent multiple tics can be mistaken for the generalized fidgetiness of ADHD. Prolonged observation may be needed to differentiate fidgetiness from bouts of multiple tics.
Specific learning disorder. Children with specific learning disorder may appear inat- tentive because of frustration, lack of interest, or limited ability. However, inattention in individuals with a specific learning disorder who do not have ADHD is not impairing out- side of academic work.
Intellectual disability (intellectual developmental disorder). Symptoms of ADHD are common among children placed in academic settings that are inappropriate to their intel- lectual ability. In such cases, the symptoms are not evident during non-academic tasks. A diagnosis of ADHD in intellectual disability requires that inattention or hyperactivity be excessive for mental age.
Autism spectrum disorder. Individuals with ADHD and those with autism spectrum disorder exhibit inattention, social dysfunction, and difficult-to-manage behavior. The so- cial dysfunction and peer rejection seen in individuals with ADHD must be distinguished from the social disengagement, isolation, and indifference to facial and tonal communica- tion cues seen in individuals with autism spectrum disorder. Children with autism spec— trum disorder may display tantrums because of an inability to tolerate a change from their expected course of events. In contrast, children with ADHD may misbehave or have a tan- trum during a major transition because of impulsivity or poor self—control.
Reactive attachment disorder. Children with reactive attachment disorder may show social disinhibition, but not the full ADHD symptom cluster, and display other features such as a lack of enduring relationships that are not characteristic of ADHD.