Prior research has demonstrated neuropsychological (NP) impairment in persons with histories of injection drug use (IDU), hepatitis C virus (HCV) infection, and methadone maintenance treatment (MMT), individually, but little is known about the NP effects of these three risk factors in combination. This issue is particularly important in China, which is addressing its highly HCV-comorbid IDU epidemic with widespread government sponsored MMT, especially in light of recent evidence suggesting that methadone may be neuroprotective in some circumstances.

We administered a comprehensive NP test battery to 195 Chinese heroin IDU individuals taking MMT (IDU+ group), the majority of whom were also HCV+ (87%; n = 169), and compared their NP performance to that of 198 demographically comparable, non-IDU Chinese controls (IDU− group). All participants in both groups tested negative for HIV infection, which is also a common comorbidity in the Chinese IDU population.

The IDU+ group did not have an increased rate of global NP impairment, or perform significantly worse on any individual NP test measure. Within the IDU+ group, liver disease characteristics and reported details of heroin use were not significantly associated with NP performance.

Failure to detect NP impairment in IDU+ subjects with or without HCV infection was surprising, particularly considering the previously demonstrated sensitivity of our NP battery to neurocognitive disorders associated with HIV infection in China. One possible explanation, which should be explored in future research, is the potential neuroprotective effect of methadone in the context of HCV infection and/or heroin withdrawal.