Anything that is smoked takes between 7 to 10 seconds to reach the brain and is even faster than injecting a substance, which takes 15 to 30 seconds. The effects of smoking marijuana are felt within a few minutes, peak at about 30 minutes and then slowly fade over two to four hours.

Users typically experience relaxed inhibitions, euphoria, increased auditory and visual awareness, as well as a greater appetite, disorientation, dry mouth and even dizziness. They also find it difficult to concentrate and learn. While the high of marijuana is gone after several hours, some mental effects such as impaired concentration and memory can be felt for days. Marijuana overdose is not lethal because although there are many more marijuana receptors in the brain than for opiates, none are located on the brain stem, which controls breathing.

Over time, the cognitive effects of sustained marijuana use are significant, but smoking marijuana also affects the lungs since it has tar, carbon monoxide, cyanide and even more benzopyrene than cigarettes, one of the primary contributors of cancer in tobacco smoke. And while users usually smoke a lower amount than cigarette smokers, because they inhale more deeply, they breathe in five times as much carbon monoxide. Chronic marijuana smokers are also likely to develop bronchitis, bronchial asthma, and even emphysema.

Long term, marijuana use disrupts normal cognitive functions such as memory and brain development, particularly in teens whose brains are not fully formed until their early 20s. Several studies have found that regular users suffered a 7-point drop in their IQ. Even those who smoked a few times a week showed significant brain abnormalities in the regions that control motivation and emotion as concluded by a recent study by Harvard and Northwestern University on 18 to 25 year-olds. In the worst cases, chronic use can trigger schizophrenia and other mental illnesses, particularly where there is a family history.

Marijuana may not be physically addictive like heroin, but 11% of Americans are psychologically dependent on the drug. In the U.S., marijuana dependency is second only to alcohol with 4.2 million chronic users as of 2014, more than twice the number for abusers of prescription opiates (1.9 million), and more than four times the number of chronic users of cocaine (0.9 million). And while many in the media have perpetuated the misleading conclusion that marijuana is not a gateway to harder drugs, existing research demonstrates that most marijuana users –especially those who began in their early teens– go on to use other drugs.

It is also important to point out that heavy marijuana users usually began smoking cigarettes and drinking alcohol earlier in life. While there is ongoing debate whether the marijuana–hard drug relationship is a question of causality or correlation, it cannot be ignored that early marijuana use is a prominent marker for the subsequent use of hard drugs. This should give pause to all those who believe that marijuana legalization is inevitable and is not a bad thing.

As a result, SmartDrugPolicy is concerned about the growing trend toward marijuana legalization — particularly its potential impact to loosen attitudes toward hard drugs like heroin. If you are interested in exploring in more detail the immediate concerns over marijuana legalization, we encourage you visit Smart Approaches to Marijuana (SAM) at

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Posted by Anaïs Faure