 Marijuana has many medical applications, most especially for patients on chemotherapy, multiple sclerosis patients, glaucoma, and for chronic pain. It has a long history of both recreational and medical use. However, its popularity has led to a lot of myths about the health effects of marijuana. I'd like to do my best to dispel these using only published, peer-reviewed studies found in Medline. I'm going to concentrate on facts, not opinions. I've listed my sources in the video description. I'm aware this is going to be an unpopular video among certain people. My motivations are strictly to correct misinformation, and if I shy away from this topic, I would be violating my own principles. If you choose to downrate or unsubscribe, please let me know through comments or personal message specifically why you are doing so. Before I start, I need to add a few disclaimers. 1. I'm a total square, a nerd, and I've never once tried marijuana or any other legal drug. I never drink to excess, I don't smoke and never have. This was a conscious choice I made in my youth. 2. I have no dog in this fight. I've never been paid to do any kind of research on illegal drugs. I have no particular political views, and I've never had illicit drugs have any major effect on my life, either positive or negative. 3. The research being presented is strictly about recreational use of marijuana cigarettes. Legal usage and other forms of drugs are not considered. 4. This is not a presentation of my political views on the legalization of POT. I would like to see less marijuana consumption, especially among young people and children, but I have no idea which policy would be most effective at achieving that end. Myth number one. Cannabis isn't addictive. Research on the topic doesn't support this common belief. The act of ingredient THC causes physical and psychological dependence in a percentage of users, estimated to be between 7 and 10 percent in some studies. Heavy users who stop using will experience physical withdrawal symptoms, similar to what an alcoholic or tobacco smoker experiences. The documented symptoms are craving, irritability, restlessness, anxiety, and depression. The symptoms peak at 2 to 4 days and subside after 7 to 10. Some studies found that about 20 percent of users are unable to voluntarily quit for more than a few days. Human withdrawal can be found in the Diagnostic and Statistical Manual of Mental Disorders, the DSM, Fourth Edition, and there are clinical trials now on your way to develop drugs to lessen the withdrawal effects. In fact, in some studies, people were more likely to successfully quit their dependence on alcohol and cigarettes than on cannabis. All of this is still fairly controversial, but well supported. POT is certainly less addictive than heroin or cocaine, but it is a drug of dependence. Myth number two, smoking marijuana is safer than cigarettes. Not according to a New Zealand study that found that after careful removal of confounders, marijuana increased lung cancer risk by 7 percent per joint year compared to 6 percent per cigarette year in young adults. How could that be? It contains up to twice the concentration of the carcinogenic polyaromatic hydrocarbons or PACs. Smokers don't use filters, hold the smoke in their lungs longer and inhale more deeply. They also absorb five times as much carbon monoxide from each puff of a joint versus the same puff of cigarette. POT smoking also increases bronchitis, airway injury, and causes immune system abnormalities in the lungs. It is significantly more likely to do these things than tobacco smoke. It also increases your chance of developing asthma and can aggravate asthma. Myth number three, being high on POT doesn't make you dangerous behind the wheel. If you use cannabis within 24 hours of driving, your risk of being in a motor vehicle accident is 2.4 times higher according to a French study. Impairment is measurable at as little as a third of a joint. These kinds of numbers may be a little deceptive because being a POT smoker means you are more likely to be young, a male, and possibly other groups with risky driving behaviors. A Dutch study found a dose-dependent response the more you smoke, the more likely you are to cause an accident from three times as likely with the first joint to seven times as likely for heavy use of three or more. Various studies have generally, but not always, found notable impairments of driving performance like braking times, lane control, and awareness of speed. One concern with marijuana is its persistence. The drug remains active in your system for much longer than alcohol. The effects of a single joint usually peak at 20 to 40 minutes, and full mental function isn't restored for two and a half hours. Multiple joints prolong this effect. Unlike alcohol, cannabis users are more likely to compensate for their impaired driving by exhibiting cautious behaviors like leaving more space, slowing down, and passing less. That may explain why they are slightly less dangerous than someone with the same impairment level with alcohol who have lost that ability to assess risks accurately. The very worst thing you can do before driving is have a few alcoholic drinks and also smoke marijuana. The two have a synergistic effect on your performance behind the wheel so that low levels of both have a stronger effect than high levels of either drug. You can't overdose on marijuana. The LD50 of Delta 9 THC by inhalation for rats is 42 mg per kilogram of body weight. For comparison, arsenic is 14 mg per kilogram orally, nicotine has an LD50 of 50 mg per kilogram orally, caffeine is 192, alcohol is over 7000. So THC is lethal at a slightly lower dose than nicotine, but about 3 times higher than arsenic. Each joint is said to contain 10 to 40 mg, so if your weight is 120 pounds, which is about 54 kg, you'd need to smoke a lot of joints before you die, but it is possible, however unlikely, especially if a vaporizer is used for rapid uptake of drug or if other drugs are used in conjunction. You can also suffer acute THC narcosis or intoxication, the equivalent to an overdose that's non-lethal but causes paralysis, unconsciousness or respiratory distress. You'd need to get to a hospital pretty quickly to avoid some life-threatening conditions. I don't think either of these is a very common problem, but it's still a myth I thought was worth correcting. I couldn't find any documented cases where marijuana alone caused a lethal overdose with normal usage, but it is found to be a contributing factor to lethal respiratory distress and some post-mortem exams. Asthma plus cannabis can be a lethal combination. Myth number five, pot is basically herbal and healthy if you discount the effects of smoking it. The worst effect in my opinion is the effect on the brain. There are so many known negative effects in the brain, I'm going to have to group them. It's worth noting that cannabinoid receptors, while they are most abundant in the brain, are also expressed in virtually every organ system, including the heart and liver. Pot negatively affects memory and learning, existing psychoses, brain development in adolescence and may worsen symptoms of depression or schizophrenia. It is a known carcinogen or cancer-causing substance and a teratogen that causes birth defects in pregnant mothers. There's new research that it's a significant risk factor in the development of psychoses like schizophrenia and bipolar disorder. The active ingredient marijuana causes changes to your brain that predispose you to psychoses and mood disorders later in life. This includes mania, schizophrenia and depression. The risk increases with how early you start and how much you smoke. Using several illicit drugs like pot and stimulants in a family history of mental illness greatly increased this risk. For example, the most conservative figures from recent studies found a population of pot smokers are between 1.2 and 2.8 times as likely to develop a psychotic disorder. Other studies less controlled for other drug use have found that high consumers of cannabis are six times as likely as non-users to develop schizophrenia within a 15-year follow-up window. This increased risk of psychoses also correlates to an increased risk of suicide. Any marijuana use made a population of Swedish men between 1.3 and 2.1 times as likely to attempt suicide. Some of you may be thinking that this is the wrong correlation. Upset people, sick people, look for escapes, drugs offer that escape. However, this has been repeatedly tested and not supported by multiple studies. Cannabis use is independently correlated to psychoses. That means no other behavioral risk factor appears to be coordinated with the marijuana use. It does seem that genetics will play a role, but that research is still preliminary. Certain people are going to be more genetically susceptible than others. In stable schizophrenic patients who have their symptoms controlled by medications, IV doses of Delta 9 THC, the active ingredient marijuana, greatly increase the symptoms of their psychotic disorders, including hallucinations, ability to discern reality, and serum markers of emotional distress. Myth 6. Pot only affects your brain and lungs. Marijuana use is positively associated with reproductive cancers, head and neck cancer, amnesia, arteritis, postural syncope, which is a condition characterized by feigning upon standing. Marijuana may trigger a myocardial infarction and have a vasospastic effect. THC interferes with fatty acid formation in the brain and reduces brain volume in long-term heavy users. If smoked, there are also oral effects similar to that of smokers, chronic bad breath, gum disease, oral infections, increased risk of cavities, periodontal disease, and precancerous lesions in the mouth. Lastly, there's a very weak correlation between marijuana use and stroke that is still the subject of active research. Just to show I'm not being completely biased, there are two negative myths that are not well supported by my survey of the scientific literature. The Gateway Drug Effect and A Motivational Syndrome. Both are still somewhat controversial, although there are studies that do suggest both effects may be real. One effect I didn't discuss was learning impairment. If you are a student and you value your education, smoking pot can reduce your ability to create long-term memory connections. Cannabis doesn't make you dumb, but it keeps you from getting full use of your education. These are just six of the myths I found being exchanged, as though they were facts. If you choose to use marijuana recreationally, I want to make sure you're aware of the health risks. I'm not interested in scare tactics, only accurate information. The government agencies whose responsibility it is to educate the public have done a very bad job in my opinion. They've used marketing techniques, which we as lifetime consumers have become resistant to. We distrust people trying to sell us something with clever ploys. My hope is that a simple cataloging of research can be more effective for people who value evidence over spin. I have two young children, five and nine, and they've already heard the drug talk. As a parent, I want them to make the right choices, not because they're afraid or because I told them to, but because they value their real lives more than comforting delusions. Thanks for watching.