Table 4.

Linear regression between smoking behavior and structural measures

	Smoking occasions/day		Joints/occasion		Joints/week		Smoking days/week
	r2	p	r2	p	r2	p	r2	p
GMd
R accumbens	0.050	0.171	0.059	0.137	0.055	0.156	0.049	0.174
R amygdala	0.071	0.100	0.035	0.251	0.007	0.610	0.027	0.321
L accumbens	0.255	0.001*	0.235	0.002*	0.141	0.020	0.115	0.035
L amygdala	0.191	0.005*	0.061	0.130	0.021	0.380	0.042	0.212
Volume
R accumbens	0.015	0.450	0.097	0.051	0.027	0.307	0.003	0.714
R amygdala	0.009	0.558	0.069	0.100	0.072	0.094	0.008	0.565
L accumbens	0.082	0.073	0.145	0.015	0.066	0.110	0.048	0.230
L amygdala	0.000	0.867	0.000	0.885	0.001	0.831	0.001	0.835
Shape
R accumbens	0.231	0.002*	0.265	0.001*	0.232	0.018	0.232	0.002*
R amygdala	0.296	< 0.001*	0.414	< 0.0001*	0.186	0.001*	0.186	0.007*
L accumbens	0.158	0.012*	0.170	0.009*	0.120	0.536	0.120	0.031
L amygdala	0.004	0.685	0.006	0.643	0.016	0.439	0.002	0.785

Values of gray matter density (GMd), volume, and shape were entered into linear regressions with the four measures of marijuana use, yielding the reported r² and p-values. p < 0.05 uncorrected are in bold; an asterisk indicates that these values met correction for multiple comparisons across four regions (e.g., p < 0.0125).