effects vertically within families, as some variants might be seen in a third or more of members of any one family (Choquet et al., 2013) but be observed in a small proportion of the general population. Fourth, for most gene variants few, if any, specific variants will be consistently identified across almost all studies, and thought might be given to developing a standard for determining which variants are worth emphasizing in additional work (e.g., Joslyn et al., 2011). Fifth, until the national alcohol and drug institutes suggest guidelines for standardizing approaches across studies, investigators should take steps to use the same measures that are already incorporated in the recent literature in an effort to minimize the variance likely to occur when study results are combined.
