Intellectual disability must involve early-childhood onset of deficits in both of the following: Intellectual functioning (eg, in reasoning, planning and problem solving, abstract thinking, learning at school or from experience) Adaptive functioning (ie, ability to meet age - and socioculturally appropriate standards for independent functioning in activities of daily life) Basing severity on IQ alone (eg, mild, 52 to 70 or 75; moderate, 36 to 51; severe, 20 to 35; and profound, < 20) is inadequate.