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Curtin University of Technology
Twins and Multiples

The Dutch Study - When separation causes problems

A study conducted by Van Leeuwen, Van Der Berg, & Boomsma (2005) with MZ and DZ twins at ages 5, 7 and 12 indicated that twins who were separated at age 5 had more internalizing and externalizing problems than nonseparated twins, as rated by both mothers and teachers. Some of these effects could be attributed to pre-existing differences between separated and nonseparated twin pairs. There were no differences found for academic achievement or for behavior problems between these groups. Therefore, the data suggest separation does not eliminate or have much an effect on behavior problems, nor does it positively or negatively affect academic achievement.

For full details see:

Van Leeuwen, M., Van Den Berg, S. M., Boomsma, D. I. (2005). Effects of twin separation in primary school. Twin Research and Human Genetics, 8: 384 391.