Anxiety disorders. ADHD shares symptoms of inattent ion with anxiety disorders. Indi-
viduals with ADHD are inattentive because of their attraction to external stimuli, new
activities, or preoccupation with  enjoyable activities. This is distinguished from the inat-
tention due to worry and rumination seen in anxiety disorders. Restlessness might be seen
in anxiety disorders. Howeve r, in ADHD, the symptom is not associated with worry and
rumination.
Depressive disorders. Individuals with depressive diso rders may present with inabil-
ity to concentrate. However,  poor concentration in mood disorders becomes prominent
only during a depressive episode.
Bipolar disorder. Individuals with bipola r disorder may have increased activity, poor
concentration, and increased impulsivity, bu t these features are episodic, occurring sev-
eral days at a time. In bipolar disorder, increased impulsivity or inattention is accompa-
nied by elevated mood, grandiosity, and ot her specific bipolar features. Children with
ADHD may show significant changes in mood within the same day; such lability is dis-
tinct from a manic episode, which must last 4 or more days to be a clinical indicator of bi-
polar disorder, even in childre n. Bipolar disorder is rare in preadolescents, even when
severe irritability and anger are prominent,  whereas ADHD is common among children
and adolescents who display excessive anger and irritability.
Disruptive mood dysregulation disorder. Disruptive mood dysregulation disorder is
characterized by pervasive irritability, and intolerance of frustratio n, but impulsiveness
and disorganized attention are not essential features. However, most  children and adoles-
cents with the disorder have symptoms that also meet crit eria for ADHD, which is diag-
nosed separately.