Monozygotic twin pairs discordant for lifetime anorexia nervosa: an exploratory investigation.

Although there is an increasing understanding of the impact of genetic factors on the development of anorexia nervosa (AN), clear identification of environmental risk factors remains unclear. Using monozygotic twins discordant for a disorder can be a useful tool for identifying such environmental risk factors. Differences between nine pairs of female monozygotic twins in the Australian Twin Registry who were discordant for lifetime AN were investigated. Twins were compared on self-report measures, including measures of current and lifetime psychopathology, temperament and coping, and parental bonding. None of the twins currently met the weight criterion for AN, indicating that current psychopathology would be unlikely to affect results. The twin affected by past AN reported a higher birth weight but a lower current body mass index than their co-twin; the affected twin tended to be more anxious than their co-twin. It may be useful for larger studies to further explore differences between twins discordant for AN in the areas of novelty seeking, and ways of coping, especially with respect to seeking social support