Quantitative evidence for distinct cognitive impairment in anorexia nervosa and bulimia nervosa.

It is generally agreed that at least some aspects of abnormal eating behaviour is indeed due in part to disordered cognition. The accumulated literature illustrates cognitive impairment in patients with anorexia nervosa (AN) and bulimia nervosa (BN). Yet beyond being inconsistent, these independent studies also do not reveal the magnitude of impairment within and across studies and fail to give due consideration to the magnitude of impairment so as to understand the severity and breadth of impairment and/or differences in cognitive profiles between patients with AN and BN. Hence, the present review on the subject sought to articulate the magnitude of cognitive impairment in patients with AN and BN by quantitatively synthesizing the existing literature using meta-analytic methodology. The results demonstrate modest evidence of cognitive impairment specific to AN and BN that is related to body mass index in AN in terms of its severity, and is differentially impaired between disorders. Together, these results suggest that disturbed cognition is figural in the presentation of eating disorders and may serve to play an integral role in its cause and maintenance. Implications of these findings with respects to future research are discussed.