Figure 7. Population continuum. CCA estimates a “population continuum” of covariation across subjects that jointly characterizes brain imaging and other (non-imaging) data through a single axis. We can describe each subject’s relation to this axis by assessing the value and polarity assigned to their individual CCA-derived subject weight and further evaluating how this value is related to the observed IDP and non-IDP measures. In this example, subjects with negative subject weights are characterized by high total cholesterol levels and low total brain volume, whereas subjects assigned with positive subject weights are characterized by low total cholesterol levels and higher total brain volume.