Science - Is marijuana an antagonist or an agonist? Why? What does it effect on the brain/body?

“In a world first,” reports The Sydney Morning Herald of Australia, “Sydney researchers have demonstrated what many people have long suspected—that memory loss and lack of concentration caused by smoking marijuana persists long after people stop using the drug.” The research, conducted at Macquarie University, confirmed that the damage marijuana causes is proportional to the amount smoked and the duration of the practice. The news gets worse: “These impairments may not be reversible.” The study showed that former users suffered the same “cognitive impairments” as those who still smoked marijuana. More than memory is affected, especially for those who have used the drug for five years or more. Such individuals were found to be slower in processing information and less able to focus their attention and avoid distractions. The report concludes that, according to the combined evidence, smoking marijuana actually changes the brain’s physiology. For more information on this subject and others, please go to jw.org "Online Library." Also for free downloads, publications or read online.