Table 2.

Structural measures of marijuana users (MJ) and controls (CON) in the amygdala and nucleus accumbens

ModalityRegionHemispherexyzMax z/FMax p-valueCluster volumea
Voxelwise significant comparisons in GMd and shape
ModalityRegionCONMJt test resultsGLM results
MeanSDMeanSDtp-valueFAdjusted p-value
ROI-based comparisons in GMd and volume
    GMdR accumbens0.440.080.470.051.310.200.950.34
R amygdala0.330.030.340.032.050.0474.470.042
L accumbens0.370.060.430.053.530.001*10.380.003*
L amygdala0.320.030.350.042.770.009*8.750.006*
    VolumeR accumbens675.40100.22709.40103.801.220.230.850.36
R amygdala1713.20222.241764.75222.810.750.460.700.41
L accumbens541.3588.87607.9586.242.160.0375.370.027
L amygdala1698.45323.561711.35323.030.150.880.010.93
ModalityRegionGroup difference (mm)t test resultsGLM results
MeanSDtpFAdjusted p
ROI-based comparisons in shape
    ShapeR accumbens0.270.403.260.002*6.730.014
R amygdala0.460.664.39<0.0001*11.240.002*
L accumbens0.170.272.840.007*8.270.007*
L amygdala−0.060.321.160.262.310.14
  • Coordinates are in MNI space and are listed in millimeters. Reported p values are uncorrected; please see Materials and Methods for whole-brain correction. Gray matter density (GMd) measures reflect ROI average density. Volume is indicated in cubic millimeters. Shape values were obtained by identifying the voxel showing the peak differences between groups within each ROI and extracting the value of that peak voxel in each individual subject. The mean difference between relative group averages is shown in millimeters. For measures, group differences between the 20 controls and 20 MJs are reported as t statistics. Individual subject values were covaried in a general linear model (GLM) to account for age, sex, alcohol use, and cigarette smoking, yielding F and adjusted p values. Values at p < 0.05 uncorrected are shown in bold; an asterisk indicates that these values met correction for multiple comparisons (e.g., p < 0.0125).

  • aGMd difference cluster volume is shown in cubic millimeters and shape difference cluster volume in square millimeters.