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. Author manuscript; available in PMC: 2020 Sep 1.
Published in final edited form as: Addict Behav. 2019 May 8;96:156–163. doi: 10.1016/j.addbeh.2019.05.007

Table 2.

Results of generalized estimating equation models predicting days per month of substance use among primary and secondary substance subgroups

Days / Month of
Cigarette Use		 Days / Month of
Alcohol Use		 Days / Month of
Illicit Drug Use
Primary
N=251		 Secondary
N=364		 Primary
N=51		 Secondary
N=165		 Primary
N=137		 Secondary
N=235
Parameter β
(Std
Error)		 β
(Std Error)		 β
(Std
Error)		 β
(Std Error)		 β
(Std
Error)		 β
(Std Error)
Intercept 3.324***
(0.017)		 3.329***
(0.012)		 2.749***
(0.129)		 2.615***
(0.094)		 3.081***
(0.069)		 2.971***
(0.068)
Treatment group
e-SBIRT −0.049
(0.029)		 −0.021
(0.019)		 0.350*
(0.165)		 0.216
(0.150)		 0.003
(0.100)		 −0.142
(0.108)
SBIRT 0.011
(0.020)		 −0.001
(0.018)		 0.037
(0.203)		 −0.059
(0.146)		 −0.117
(0.100)		 0.002
(0.094)
EUC Reference Reference Reference Reference Reference Reference
Month (Linear effect of time) −0.033**
(0.012)		 −0.056***
(0.013)		 −0.328
(0.195)		 −0.070
(0.088)		 −0.099*
(0.045)		 −0.131**
(0.044)
Month*Month (Quadratic effect of time) 0.001
(0.002)		 0.004*
(0.002)		 0.041
(0.026)		 −0.003
(0.014)		 0.005
(0.007)		 0.012±
(0.007)
Treatment × (Linear) Time Interaction
Month * e-SBIRT −0.052
(0.027)		 −0.025
(0.024)		 0.090
(0.211)		 −0.238*
(0.117)		 −0.181*
(0.085)		 −0.053
(0.076)
Month * SBIRT −0.067*
(0.029)		 −0.032
(0.024)		 −0.099
(0.278)		 −0.310*
(0.130)		 −0.077
(0.078)		 −0.046
(0.067)
Month * EUC Reference Reference Reference Reference Reference Reference
Treatment × (Quadratic) Time Interaction
Month*Month * e-SBIRT 0.005
(0.004)		 0.002
(0.003)		 −0.014
(0.028)		 0.035*
(0.018)		 0.028*
(0.012)		 0.009
(0.011)
Month*Month * SBIRT 0.009*
(0.004)		 0.004
(0.004)		 0.011
(0.036)		 0.048*
(0.019)		 0.014
(0.011)		 0.007
(0.010)
Month*Month * EUC Reference Reference Reference Reference Reference Reference
Pregnant (vs. not pregnant) −0.118*
(0.055)		 −0.145**
(0.052)		 −0.828***
(0.230)		 −1.299***
(0.372)		 −0.239
(0.173)		 −0.482**
(0.171)

Abbreviations: e-SBIRT, electronically-delivered Screening, Brief Intervention and Referral to Treatment; SBIRT, clinician-delivered Screening, Brief Intervention, and Referral to Treatment; EUC, Enhanced Usual Care;

*

p < 0.05;

**

p < 0.01;

***

p < 0.001