The Science of CBD/Marijuana and its Long-Term Effects on the Brain

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The trend toward legalization of cannabis and CBD means many people are giving greater thought to their effects. Even for many people who aren’t familiar with the mechanisms of the brain the short-term effects of CBD and cannabis are more familiar. The long-term effects, however, are even less known but certainly as contentious.

Some long-term effects of cannabis and CBD use are simply continuations of short-term effects. Fat attracts THC, and since cell walls are composed largely of fat, THC is immediately sucked up by every cell in the body. Then, it is re-released gradually, which is why THC can be detected by tests up to a month after use. It is also thought that many short-term effects, such as impaired driving and memory, can also endure. For more information, check out marijuana at i49.

Clinical Testing

Many clinical tests have found that as long as THC remains in the brain, it continues to affect the brain. What is in question is whether marijuana actually changes the brain. After the last traces of THC have left the brain, can the brain function as if never altered for months, and even years later?

Unfortunately, few of the studies already conducted have addressed this question, and the resulting lack of clarity has added fodder for debate. In an effort to remove some of this ambiguity, the National Institute for Drug Abuse published a summary in the New England Journal of Medicine addressing the long term effects of marijuana and CBD use. What follows are a few of their findings.


Marijuana use is addictive. Almost 1 in 10 people who use marijuana will eventually become addicted according to a report issues by the National Epidemiologic Survey on Alcohol and Related Conditions.

Hindrance in Brain Development

Throughout our lives, our brains mold and develop, but from birth until about our 21st birthday, our brains are particularly malleable. A team of scientists from the University of Melbourne, Australia performed a study of MRI scans of marijuana users who started in adolescence and another group who never smoked. The results showed that neural connections in marijuana users showed significant impairment compared with those who did not smoke.

A big issue in this study was the factor that the study did not show that the brains had been changed as a result of the smoking since they could have been different before the study took place. This allows scientists to show that although the proof is not unassailable, the evidence is powerful. Supporting this conclusion, for example, is another study conducted by New Zealand researchers that showed individuals from birth to age 38 had lower IQs in their thirties as compared with their childhood.

The declines in IQ were not thought to be associated with personality or other factors. The people who had started smoking the youngest and smoked heavily showed the largest drop in mental performance.

The Verdict

It is clear from the differences in these studies that long-term effects of marijuana and CBD have much to be determined. Studies do suggest that there are changes that take place in the brains of marijuana users, especially if the use is while the brain is still developing. The conclusions reached so far may be a bit premature, but they show considerable room for doubt.

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