Cannabis Users and Premorbid Intellectual Quotient (IQ)‏

Abstract

• The chapter focuses on premorbid Intellectual Quotient (IQ) in cannabis users, one of the most controversial topics in studies on the harmful effects of cannabis use on cognition. • Several studies have ascertained acute and residual effects of cannabis use in the memory domain, but only a minimal general cognitive effect after a long-term period of abstinence. • A number of longitudinal studies were able to obtain IQ measures before and after cannabis consumption, but they yielded discordant findings. • Authors, however, observed a relationship between higher premorbid IQ and recreational or discontinued use while a lower premorbid IQ resulted as a predictor for regular or heavy cannabis use. • Studies on cannabis use and cognitive impairment associated with schizophrenia paradoxically found better IQ among patients with cannabis use lifetime. • At the end of the chapter, authors proposed a conceptual table to summarize the complex relationship between premorbid IQ and cannabis use in determining different outcomes, by sustaining the hypothesis of a shared genetic vulnerability to psychosis and cannabis use,which is reflected on premorbid IQ and able to influence the contact with the substance. • In turn, cannabis may be a trigger for psychosis towards this continuum of a neurodevelopmental vulnerability.