Generally speaking, I'm very pro the legalization of cannabis (although I personally don't like or use it), but this new study should be given some serious attention. From the Independent:
Teenagers who smoke cannabis regularly could be permanently damaging the development of their brain and are likely to end up with significantly lower IQ scores than teenagers who do not use the illicit drug, a major study has found.
People who started smoking cannabis as adolescents were found at the age of 38 to be still suffering from a drug habit they had started more than 20 years earlier, scientists said....
Scientists said that the study is the first to show that cannabis use in adolescence – but not cannabis use that begins in adulthood – can cause a significant long-term decline in IQ that does not appear to be reversible when people stop using cannabis.
The researchers believe this is evidence that cannabis can interfere with the development of the adolescent brain, which continues to undergo neural growth and "rewiring" during early teenage years....
The study used data gathered from a cohort of 1,037 children born in 1972-73 in Dunedin, New Zealand. IQ tests carried out when they were 13 were compared with IQ tests completed when they were 38.
This is purely anecdotal, but I have noticed that many of my friends who smoked a lot of marijuana when growing up have suffered from a multitude of personal and professional problems, ranging from severe mental illness to chronic unemployment and professional under performance. I have other friends who started smoking weed later on in life, and it hasn't seriously affected their psychological well being or professional lives. This isn't meant to pass judgment - just an honest observation that I think the majority of my friends would agree with. The evidence linking weed to psychosis and schizophrenia is fairly well established, and this new study compounds the thesis that marijuana actively changes and damages the brain in its formative years.
Of course, excessive alcohol use is incredibly damaging and there's no reason why one is legal and the other isn't, but teenagers generally don't use the substances in the same way. Many of my friends would smoke weed on a daily basis, taking joints to school and smoking them on lunch breaks. I can't remember a single friend using alcohol in the same way, meaning alcohol abuse was far less prevalent.
Does this hurt the legalization of cannabis movement? Probably, given the hysterical reaction of politicians to anything drug related. And despite its seriousness, it really shouldn't. There's a strong argument to be made that most drugs should be legalized as there's little evidence that banning them does any good. It simply creates black markets and crime around an issue that should be treated like alcohol. And like alcohol, drugs should have strict age restrictions to limit teenage use.
The new study shouldn't stop the march towards the legalization of cannabis, but it should be used to help educate its users. There are clear dangers from taking the drug at an early age, and teenagers need to know about it.