Cognitive Intraindividual variability in injection drug use among Hispanic residents of Puerto Rico.

Despite a high prevalence of injection drug use (IDU) in Puerto Rico, little is known about how it affects neuropsychological functioning in this population. Investigations of intra-individual variability (IIV) have alluded to its utility as a potential indicator of neural decline. The purpose of this study was to characterize IIV among Hispanic residents of Puerto Rico who engage in IDU. Injectors and non-injectors completed the Neuropsí Atención y Memoria battery. Measures of IIV were calculated for the overall test battery (OTB), the three battery indices, and three domains of attention, memory, and executive functioning. The injector group showed significantly greater IIV than the non-injector group on all measures (OTB, indices, and individual domains). Additionally, injectors showed significantly higher IIV in the domain of executive functioning compared to other cognitive domains and battery indices. In contrast, non-injectors did not show any significant within-group differences on any IIV measures. The higher performance variability observed in the IDU group suggests a negative influence of IDU on cognition, with executive functioning being more susceptible to these effects. These findings support the need for continued investigations into the clinical application of IIV for diagnostic and prognostic purposes in the Hispanic IDU population.