Intellectual functioning of adolescent and adult patients with eating disorders

Intelligence is a known vulnerability marker in various psychiatric disorders. In eating disorders (ED) intelligence has not been studied thoroughly. Small-scale studies indicate that intelligence levels might be above general population norms, but larger scale studies are lacking. The aim of this study was to determine intellectual functioning in ED patients and associations with severity of the disorder.

Wechsler's Full scale IQ (FSIQ), Verbal IQ (VIQ) and Performance IQ (PIQ) of 703 adolescent and adult ED patients were compared with population norms. Exploratory analyzes were performed on associations between IQ and both somatic severity (BMI and duration of the disorder) and psychological/behavioral severity (Eating Disorder Inventory [EDI-II] ratings) of the ED.

Mean IQ's were significantly higher than population means and effect-sizes were small-to-medium (d = .28, .16 and .23 for VIQ, PIQ, and FSIQ). No linear associations between IQ and BMI were found, but the most severely underweight adult anorexia nervosa (AN) patients (BMI ≤ 15) had higher VIQ (107.7) than the other adult AN patients (VIQ 102.1). In adult AN patients PIQ was associated with psychological/behavioral severity of the ED.

Our findings suggest that, in contrast with other severe mental disorders where low intelligence is a risk factor, higher than average intelligence might increase the vulnerability to develop an ED. © 2016 Wiley Periodicals, Inc.(Int J Eat Disord 2017; 50:481-489).