 The evidence evidently clearly indicates that long-term marijuana use can lead to addiction. Approximately 9% of those who experiment with marijuana will become addicted, and that number goes up to about 1 in 6 among those who start marijuana as teenagers and to 25 to 50% among those who smoke marijuana daily. By addiction, what they're talking about is like the colloquial definition and acquired chronic relapsing disorder that's characterized by a powerful motivation to continually engage in an activity despite persistent negative consequences. You may want to stop, but when you try, you may suffer withdrawal symptoms that make it hard to quit. This withdrawal syndrome affects about 50% of daily users and typically begins 1 to 2 days after stopping, peaks at 2 to 6 days, but the craving, sleeping problems, nightmares, anger, irritability, unease, and nausea goes away after 1 or 2 weeks. Marijuana now has this reputation as being benign, non-habit-forming, and that may be true for most users, certainly less addictive than many other drugs like alcohol. Only about half the dependence risk compared to heroin or cocaine, less than a third as habit-forming as tobacco, but 9%—1 in 11 users, 1 in 6 for those starting in their early teens, is hardly an inconsequential percentage, given that about 20 million Americans actively use this stuff. However, not all varieties of cannabis are equally addictive. Hypotency strains have been associated with a greater severity of dependence, but that's the stuff people prefer. This is not your grandmother's grass. Based on 38,000 samples of marijuana confiscated by the DEA, the potency has tripled in recent years, from 4% THC up to around 12%. With Denver and California now up around 15, and Seattle pushing 20. That's 15 times more powerful than pot from the 70s. So like 15 joints all rolled up into one. Yeah, but don't users know this and titrate their dose accordingly, using less of the more potent pot? Yes, but they don't compensate fully, and so do end up getting higher doses, perhaps reflected in the increase in emergency room visits in Colorado for marijuana intoxication after legalization. Parallels have been drawn with the tobacco industry, intentionally boosting nicotine levels of their products to make them more addictive, but where that analogy breaks down is in the consequences of that addiction. Every year, tobacco kills 25 times more people worldwide than all illicit drugs combined. Alcohol kills about 10 times more, and cannabis alone probably contributes little to overall mortality, at least. So one has to consider the outcomes of substance dependence. Caffeine can be addictive too, but if it gets you to drink more green tea, then great. The consequences of consuming this leaf, as opposed to this leaf, depends on the health consequences, which we'll cover next.