Among surface area measures, there were significant standardized genetic covariances (-0.17 < covA < -0.13, p = 0.01-0.04) between pack-years and the frontal lobe and cingulate cortex ROIs, with significant negative phenotypic correlations (-0.14 < rP < -0.08, p = 0.02-0.04). These regions include left rostral anterior cingulate, right caudal anterior cingulate, right pars opercularis, and left frontal pole (Table II). The magnitude of the genetic covariance was fairly consistent across adjusted and unadjusted measures of surface area. The average genetic covariance among unadjusted ROIs was -0.15 while those adjusted for total surface area was -0.13 (Table III).
