A large Swedish study confirms the importance of vigilance for crossover during treatment.
Although anorexia nervosa and bulimia nervosa are distinct eating disorders, they share some symptoms, and crossover is common. A recent report from Sweden has added new data showing that genetic and environmental mechanisms underlie mechanisms for both genetic and environmental actions in patients with AN and BN (Psychol Med. 2010. 51:62).
Dr. Shuyang Yao of the Karolinska Institute, Stockholm, and colleagues used several national health registers in their study, including the Swedish Population Register and the Multi-generation Register, to include 782,938 randomly selected full sisters and maternal half-sisters born in Sweden between 1970 and 2005. The researchers found that 6104 (0.9%) of the full sisters and 938 (0.82%) of maternal half-sisters had been diagnosed with AN. Of the full sisters, 3142 (0.47%), and 79 of the maternal half-sisters (0.51%) had been diagnosed with BN. Both disorders were diagnosed in 679 (0.10%) of full sisters and IN 122 (0.11%) of maternal half-sisters.
Analyses showed that that the genetic and environmental effects are both relevant and that they overlapped in those with AN and BN. These findings demonstrate the contribution of both genetic and environmental factors and support conceptual overlap between AN and BN. We know this to be true at a clinical phenomenon level, and this study provides some explanation for what is seen clinically.