F90 — Hyperkinetic disorders

Concept, in one sentence

Inattention, overactivity, and impulsiveness, evident before age 6 and pervasive across more than one setting — not a single-classroom pattern.

Decisive boundary cues

• Confirmed in more than one setting (e.g. home and school) -> weighs toward F90.
• Confined to one chaotic or understimulating setting only -> weighs toward a situational explanation, not F90.
• Full pervasive-developmental triad also present -> weighs toward also considering F84.

Duration/course cue

Onset before age 6, persistent over time — not a recent or brief change.

Nearest alternatives

F91, F84, F93

Common mistake

Confirming F90 from a single setting's report alone, without checking for corroborating evidence from a second setting.

Retrieval prompt — one-line memory anchor

What second source of information would you need before confirming this is pervasive across situations?