Figure 2. Sample characteristics of the extant MRI twin studies on typical populations.
Note: To facilitate comparisons with singleton and sibling subsamples, individual twins are counted rather than twin pairs. Several reports share overlapping samples, either derived from the National Heart, Lung, and Blood Institute sample (1), the Netherlands Twin Registry (2), or NIMH’s longitudinal pediatric imaging study (3).
* = reports based on data from pediatric populations.
