Do twin studies overestimate heritability (for instance by putting the interaction between environment and genome under the label "heritable")? If so why? Would you have any research papers to point me to?
It seems likely that some percentage of twin studies would fail to account for all the systematic environmental variables that connect their twins. In this case, the effects of these variables would still cause a correlation, which would be attributed to heritability. "A second look at twin studies" by Lea Winerman discusses examples of these types of variables.