ABSTRACT. Objective. The goal of this study was to examine the relative contributions of growth deficiency and psychosocial factors to cognitive development in toddlers with infantile anorexia.Methods. Eighty-eight toddlers, ranging in age from 12 to 33 months, were enrolled in this study. Toddlers were evaluated by 2 child psychiatrists and placed into 1 of 3 groups: infantile anorexia, picky eater, and healthy eater. All 3 groups were matched for age, race, gender, and socioeconomic status (SES). Toddlers underwent nutritional evaluations and cognitive assessments with the Bayley Scales of Infant Development. Toddlers and their mothers were also videotaped during feeding and play interactions, which later were rated independently by 2 observers.Results. On average, toddlers with infantile anorexia performed within the normal range of cognitive development. However, the Mental Developmental Index (MDI) scores of the healthy eater group (MDI ؍ 110) were significantly higher than those of the infantile anorexia (MDI ؍ 99) and picky eater (MDI ؍ 96) groups. Within the infantile anorexia group, correlations between MDI scores and the toddlers' percentage of ideal body weight approached statistical significance (r ؍ .32). Across all groups, the toddlers' MDI scores were associated with the quality of mother-child interactions, SES level, and maternal education level. Collectively, these variables explained 22% of the variance in MDI scores.Conclusions. This study demonstrated that psychosocial factors, such as mother-toddler interactions, maternal education level, and SES level, are related to the cognitive development of toddlers with feeding problems and explain more unique variance in MDI scores than nutritional status. Pediatrics 2004;113:e440 -e447. URL: http://www.pediatrics.org/cgi/content/full/113/ 5/e440; failure to thrive, feeding disorder, infantile anorexia, cognitive development, growth deficiency, mothertoddler interactions.ABBREVIATIONS. FTT, failure to thrive; SES, socioeconomic status; MDI, Mental Developmental Index; BSID, Bayley Scales of Infant Development. F ailure to thrive (FTT) describes children who exhibit growth deficiency, as indexed by faltering or stunted growth. Several studies suggest that FTT is associated with poorer cognitive development, learning disabilities, and long-term behavioral problems. [1][2][3] More recently, Corbett et al 4 detected a significant association between the severity of growth deficiency and IQ, whereas Raynor and Rudolf 5 found that 55% of the infants who were failing to thrive exhibited developmental delay. In addition, a study by Reif et al 6 reported that children with a history of FTT were found to have more learning difficulties and evidenced developmental delay at follow-up 5 years after the initial presentation.These findings from the pediatric literature have led many to believe that FTT alone is sufficient to cause developmental delays. However, a critical problem with many previous studies is that FTT is frequently confounded with psychoso...