Our analysis distinguished visual and sensorimotor regions as principal areas where the rsFNC might be reduced due to alcohol or nicotine use. The significant hypo-connectivity of SMK, SAD and DRN subjects when compared to the CTR subjects revolved around these RSN groups. Other RSN groups affected by both smoking and drinking were ECN, SAL and PRE indicating the existence of common effects across the brain. These results agree with the detriment of network global efficiency previously observed in both smokers (Fedota and Stein, 2015; Lin et al., 2015) and drinkers (Sjoerds et al., 2015). Few differences were detected when the post-hoc analysis in our data compared rsFNC differences of SAD vs. DRN and SAD vs. SMK groups indicating that common effects cannot differentiate between the substances. A different study found an opposite outcome among visual, sensorimotor, cuneus and insula areas in subjects using cocaine, marijuana and alcohol, but this hyper-connectivity was observed after abstinence periods longer than 4 days (Wang et al., 2015). These rsFNC dysfunctions likely specify effects that may be commonly linked to multiple substances of abuse where
