F70 — Mild mental retardation

Concept, in one sentence

Subnormal intellectual functioning (approximately IQ 50-69) AND a matching adaptive-functioning deficit, present since the developmental period — never either criterion alone.

Decisive boundary cues

• A matching adaptive-functioning deficit alongside subnormal IQ, since childhood -> weighs toward F70.
• Below-average IQ alone, with typical everyday adaptive functioning -> weighs toward borderline functioning, not F70.
• A previously typical baseline with a later, datable decline -> weighs toward dementia (F00-F03), not F70.

Duration/course cue

Onset during the developmental period, persisting as a stable pattern rather than a discrete episode.

Nearest alternatives

F71, F79, F00

Common mistake

Treating a single below-average test score as sufficient on its own, without checking the matching adaptive-functioning picture.

Retrieval prompt — one-line memory anchor

What single additional piece of information would you ask for to confirm this is F70 rather than borderline functioning?