While many people shrug off marijuana as a harmless drug, it is much more serious than that. Heavy marijuana use, those who use marijuana 20 times or more per month, has increased 80 percent since 2008. Contrary to popular belief, it can be addictive, cause memory and learning problems, hallucinations, delusions and depersonalization. Now, we’re finding out another terrible side effect of weed. A New Zealand study released in August revealed just how damaging the long-term effects of habitual pot smoking can be. The research project, which you can read more about here, tested the participants’ IQ at age 13 and again at age 38. The only group that saw a significant decline in IQ scores was comprised of individuals who started regularly smoking pot before the age of 18. The average age an Arizona child tries marijuana for the first time is 13, the age the study assumed to be “before any significant marijuana use.” So what does this mean for those younger habitual pot smokers? We’d rather not know. Marijuana can be difficult for teens to understand, especially with recent news coverage around “medical” marijuana and efforts to legalize the drug. Here’s some help for talking with your teens about marijuana.