Characteristics of Monozygotic Twins Discordant for Anorexia Nervosa: Comprehensive Risk Evaluation for Anorexia Nervosa in Twins (CREAT) Study

Objective To characterise the clinical and phenotypic profile of the Comprehensive Risk Evaluation for Anorexia nervosa in Twins (CREAT) cohort, identify candidate risk and illness‐related correlates of AN, and establish a foundation for forthcoming biological, neuroimaging, endocrinological, and microbiota studies. Methods MZ twins discordant for lifetime AN (44 individuals) and control MZ twin pairs (42 individuals) were recruited. Analyses included total‐sample associations with AN, between‐group comparisons (affected, unaffected co‐twins, controls), and within‐pair analyses of discordant twins. Results Affected twins, most of whom were weight‐restored and non‐acute, differed markedly from unaffected co‐twins and controls. Lifetime AN was associated with higher perfectionism, goal‐directed drive, neuroticism, behavioural inhibition, impulsivity, broader psychiatric symptoms, teasing history, autism symptoms, and lower quality of life. Within‐pair analyses implicated perfectionism, goal‐directed drive, and competency‐related teasing as candidate individual‐specific risk factors for AN, with evidence of additional associations with impulsivity, behavioural inhibition, neuroticism, broader psychiatric symptoms, and autism symptoms. Conclusion Findings support a multifactorial model of AN involving individual‐specific influences and shared familial liability. Perfectionism, goal‐directed drive, and competency‐related teasing emerged as candidate individual‐specific risk factors, while the pattern of elevations, with unaffected co‐twins often falling between affected twins and healthy controls, suggests that several clinical and phenotypic features may reflect familial liability for AN.