F90 vs F91
F91 — Conduct disorders
Distinguish attention/activity regulation difficulty (F90) from a persistent pattern of rule-violating, aggressive, or defiant conduct (F91), using which feature is primary — while recognising the two frequently co-occur and are captured together by F90.1 when both are genuinely present.
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Show overlap — what both share
A restless, impulsive child with F90 can appear disobedient or oppositional because impulsive actions frequently break rules unintentionally, and a child with F91 can appear inattentive or overactive as part of a broader defiant or aggressive presentation, so either category can be mistaken for the other from behaviour alone.
Show decisive evidence
- F90 is primarily about inattention, overactivity, and impulsiveness, evident before age 6 and pervasive across settings, without requiring a persistent pattern of aggressive or rule-violating conduct.
- F91 is primarily about a persistent pattern of dissocial, aggressive, or defiant behaviour, typically judged over 6 months or more, without requiring the attention/activity regulation difficulty F90 requires.
- Rule-breaking that arises from impulsivity and poor self-regulation, without a broader pattern of aggression, defiance, or dissocial acts, favours F90 alone.
- A persistent pattern of aggression, defiance, or dissocial behaviour with normal or near-normal attention and activity regulation favours F91 alone.
- When both a hyperkinetic pattern and a genuine conduct-disorder-level pattern are independently present, F90.1 (hyperkinetic conduct disorder) captures the combination.
What weakens F90: A persistent pattern of aggression, defiance, or dissocial acts without the core attention/activity features weakens F90 as the primary classification; conversely, attention/activity difficulty without a persistent conduct pattern weakens F91.
Show duration / course
F90 requires onset before age 6 and persistence over time; F91 requires a persistent pattern typically judged over 6 months or more — both require persistence, but over different specific features (attention/activity versus conduct).
Show exclusions / context
Per each category's own exclusions_distinctions entries, a hyperkinetic pattern with a genuinely co-occurring conduct disorder is coded as F90.1 rather than treating the two as mutually exclusive alternatives.
Show information still needed
Whether the primary, decisive feature is attention/activity regulation difficulty (pointing to F90), a persistent pattern of aggressive or rule-violating conduct (pointing to F91), or genuinely both together (pointing to F90.1).
Show the common trap
Treating any rule-breaking or disobedient behaviour in a restless, impulsive child as evidence of a conduct disorder, without checking whether a persistent, independent pattern of aggression or dissocial acts is actually present.
Mini challenge — practise this distinction
Apply the discriminating evidence above to a fresh case before checking the full feedback.