Table 2.

Multilevel models (MLM) examining change in observed BrAC during intravenous self-administration (Session 2) as a function of time and between-person moderators (subjective stimulant and sedative response to alcohol during Session 1 and OPRM1 genotype).

Fixed Effects	B	SE	t	p
Model 1: Unconditional Effect of Time
Time contrasts (Level 1)
Linear	27.37**	1.78	15.42	<.001
Quadratic	−5.19**	0.44	−11.90	<.001
Cubic	0.30**	0.04	7.47	<.001
Model 2: Subjective Response
Between-person (Level 2)
Peak Stimulation (session 1)	0.21	0.94	0.23	.821
Peak Sedation (session 1)	0.08	0.94	0.09	.932
Interactions with Time
Peak Stimulation*Linear	3.64*	1.70	2.15	.034
Peak Stimulation*Quadratic	−0.92*	0.44	−2.11	.036
Peak Stimulation*Cubic	0.08†	0.04	1.93	.055
Peak Sedation*Linear	−3.73*	1.69	−2.20	.030
Peak Sedation*Quadratic	0.65	0.43	1.50	.134
Peak Sedation*Cubic	−0.04	0.04	−0.94	.350
Model 3: OPRM1 Genotype
Between-person (Level 2)
Race (0=white; 1=nonwhite)	0.02	0.98	0.02	.985
Genotype (0=AA; 1=GA/GG)	−1.66	2.21	−0.75	.454
Interactions with Time
Race*Linear	0.02	1.76	0.01	.992
Race*Quadratic	0.12	0.44	0.28	.779
Race*Cubic	−0.01	0.04	−0.35	.727
Genotype*Linear	13.78**	3.96	3.48	.001
Genotype*Quadratic	−3.66**	0.99	−3.70	<.001
Genotype*Cubic	0.30**	0.09	3.20	.002

Note. Unstandardized parameter estimates shown. Estimates of fixed effects are shown; random intercepts and random slopes for all time contrasts were estimated in all models but are not shown in the table to conserve space. Time contrasts are estimated at the within-person level (level 1) and subjective response and genotype are modeled at the between-person level (level 2). Time was coded with the post-priming BrAC measurement (15 min) as T=0 and an interval of 1 between each successive BrAC measurement. Peak stimulation and peak sedation are grand-mean centered and standardized across participants (i.e., z-scored); ^†p<.10; *p<.05; **p<.01.