Does cognitive functioning improve with weight restoration? An examination of changes in intelligence quotient scores in adolescents with anorexia nervosa before and after treatment.

Intelligence Quotient (IQ) scores, typically considered stable throughout life, may be impacted by anorexia nervosa (AN). This study investigated whether IQ scores change following treatment in adolescents with AN (N = 110; age = 14.65 ± 2.49 years; 85% female). We analyzed changes in vocabulary, matrix reasoning, and full-scale IQ (FSIQ-2) scores on the Wechsler Abbreviated Scale of Intelligence, with developmental weight suppression and duration of illness as covariates. Results indicated end of treatment improvements in vocabulary (F(1, 107) = 7.46, p = .01, η_p² = .07), matrix reasoning (F(1, 107) = 4.44, p = .04, η_p² = .04), and FSIQ-2 (F(1, 107) = 11.00, p < .01, η_p² = .09) scores. A shorter illness duration was associated with greater gains in vocabulary (p = .04) and FSIQ-2 (p = .02) scores. These findings suggest that IQ scores can improve throughout treatment, with shorter illness duration linked to greater improvements, underscoring the importance of early nutritional intervention.