Delay discounting is greater among drug users seropositive for hepatitis C but not HIV.

Substance dependent individuals (SDIs) tend to make impulsive choices that favor more the prospect of attractive immediate rewards rather than a positive outcome in the future (Bechara, Damasio, Tranel, & Damasio, 1997). This bias toward choices with immediate (as opposed to future or delayed) outcomes is evident among SDIs even when a larger reward is available if the subject chooses to wait. This pattern of steep intertemporal choice or increased delay discounting, the tendency to devalue delayed rewards, has been demonstrated in numerous studies of individuals dependent on various substances, including cocaine, methamphetamine, and opioids (Bickel, Koffarnus, Moody, & Wilson, 2014) as well as non-drug using groups with disinhibitory behavior disorders (Paloyelis, Asherson, Mehta, Faraone, & Kuntsi, 2010). Further, studies have linked increased discounting rates with key substance use treatment outcomes, including relapse (Sheffer et al., 2014). The construct of delay discounting has added significance for SDIs living with HIV/AIDS as a potential contributing mechanism of risky sexual and injection practices (Sheffer et al., 2014) as well as poor adherence with antiretroviral therapy. However, few studies have investigated discounting performance among HIV+ individuals with or without substance use disorders. An important study by Meade and colleagues investigated neural mechanisms of discounting performance using fMRI in a group of 39 HIV+ individuals (Meade, Lowen, MacLean, Key, & Lukas, 2011). They reported that HIV+ individuals who had recently used cocaine showed significantly higher discounting rates and decreased activation in frontoparietal cortex compared with HIV+ individuals with previous or no cocaine use. All participants in the Meade study were HIV+, raising the question if a positive HIV serostatus is associated with higher discounting rates compared with HIV− risk-matched controls. Infection with the hepatitis C virus (HCV) is highly prevalent among SDIs and potential effects of HCV or HIV and substance use on discounting rates might increase risk of virus superinfection, exposure or transmission by augmenting the propensity toward risky sexual and injection practices. Huckans and colleagues reported increased discounting rates among HCV+ compared with HCV− individuals (Huckans et al., 2011). Additionally, cognitive impairment is significantly more common among individuals coinfected with HIV and HCV compared with monoinfected and uninfected individuals (Cherner et al., 2005; Hilsabeck, Castellon, & Hinkin, 2005; Martin-Thormeyer & Paul, 2009). The aim of the present study was to investigate the potential separate or additive effects of HIV and HCV on delay discounting performance in a sample of SDIs. Study results have potential clinical significance: cognitive enhancement training can improve delayed discounting among SDIs (Bickel et al, 2011). SDIs with concurrent HIV or HCV infection may derive additional benefit from substance abuse treatment programs incorporating these techniques. The results of this study may help to identify which group (HCV+ or HIV+) will benefit most from this type of intervention in order to modify risk-taking behavior and prevent co-infection or relapse.