Table 1.

Studies Assessing Discounting of Delayed Monetary Rewards

Study	Substances	Group 1	N	Group 2	N	Estimated Effect Sizea	Significant Group Difference
Alcohol
Kirby and Petry 2004	Opioids, Cocaine, Alcohol	Alcohol	33	Heroin	27	0.88	Yes
		Alcohol	33	Cocaine	41	0.66	No
Moallem and Ray, 2012	Alcohol, Nicotine	Alcohol + Nicotine	213	Nicotine	67	0.16	No
		Alcohol + Nicotine	213	Alcohol	107	0.31	Yes
		Alcohol	107	Nicotine	67	—	No
Taylor et al. 2016	Alcohol, Polysubstance	Alcohol	27	Polysubstance	59	0.00	No
Moody et al. 2016b	Cocaine, Alcohol, Nicotine	Alcohol	47	Nicotine	137	0.12	No
		Alcohol	47	Cocaine	28	0.19	No
Cocaine
Bornovalova et al. 2005	Cocaine, Opioids	Cocaine	16	Heroin	11	0.93	Yes
García- Rodríguez et al. 2013	Cocaine, Nicotine	Cocaine	17	Nicotine	30	1.18	Yes
		Cocaine + Nicotine	30	Nicotine	30	1.44	Yes
		Cocaine + Nicotine	30	Cocaine	17	0.35	No
Mejía-Cruz et al. 2016	Cocaine, Marijuana	Cocaine	77	Marijuana	44	—b	No
Moody et al. 2016b	Cocaine, Alcohol, Nicotine	Cocaine	28	Nicotine	137	0.63	Yes
Opioids
Kirby and Petry 2004	Opioids, Cocaine, Alcohol	Heroin	27	Cocaine	41	0.20	No
Robles et al. 2011	Opioids	Methadone only	30	Methadone + illicit opioids	30	<0.30	No
Karakula et al. 2016	Opioids	Heroin	106	Prescription- opioids	33	0.49	Yes
Polysubstance
	Polysubstance	Polysubstance	25	Nicotine	20	<0.18	No
Businelle et al. 2010		Polysubstance + Nicotine	36	Nicotine	20	<0.18	No
		Polysubstance + Nicotine	36	Polysubstance	25	<0.18	No

^aEffect size is reported as Cohen's d. If this was not reported, it was calculated by a) means and standard deviations, b) test-statistics and degrees of freedom, or c) conversion from another measure of effect size.

^b— Indicates lack of information

^cThis study compared nicotine, alcohol, and alcohol + nicotine groups using three different monetary reward magnitudes: small, medium, and large. There was no effect of group on medium or large rewards, but there was an effect of group on the small reward values, such that the alcohol + nicotine group showed steeper delay discounting relative to both the alcohol and nicotine group.