Valuation system connectivity is correlated with poly-drug use in young adults

Poly-drug consumption is a dangerous, yet complex model of substance use that contributes to many cases of imprisonment and fatal overdose. Despite the growing number of studies looking at this phenomenon, there remains a lack of neuroimaging data elucidating the neural markers of poly-drug use. In particular, the valuation system, tasked with weighing the value of items and experiences, may hold significance in understanding the motivations behind poly-drug use. To this end, we sought to analyze the functional connectivity of the Valuation System (VS), Executive Control System (ECS) and Valuation-Control Complex (VCC) of drug-using participants in the Human Connectome Project Healthy Young Adult dataset (n=992). Using multivariate regression, network-averaged connectivities were correlated with various substance use measures (stimulants, cocaine, hallucinogens, opiates, sedatives and marijuana) and demographic variables (gender, parental use history). We found that the VS, ECS and VCC were all correlated with drug use behaviour either as individual systems or when paired with other substances. Both VS (R2= 0.53) and ECS (R2= 0.55) connectivity are positively correlated with stimulant use whereas both ECS (R2= 0.45) and VCC (R2= 0.045) connectivity are negatively correlated with marijuana use. VS (R2= 0.75) and VCC (R2= 0.74) connectivities are also negatively correlated with sedative use. Additionally, network connectivity was correlated with drug use behaviour via two-way interactions with other substances. These findings provide preliminary indications of the consequences of poly-drug use in healthy young adults.