Although his findings point to potential benefits of smoking pot, Zhang says that he does not endorse its use. “Marijuana has been used for medicine and recreation for thousands of years,” he says. “But it can also lead to addiction.”
They found that HU210 seemed to induce new brain cell growth, just as some antidepressant drugs do, they report in the Journal of Clinical Investigation 1 . This suggests that they could potentially be used to reduce anxiety and depression, Zhang says. He adds that the research might help to create new cannabinoid-based treatments.
University of Texas Southwestern Medical Centre, Dallas
Many drugs, such as heroin, cocaine and alcohol, inhibit the growth of new cells in the hippocampus, which scientists believe could emotionally destabilize addicts. Understanding how drugs affect the hippocampus may have a critical role in treating addiction.
Expanding the mind
Finally, she says, scientists must understand why cannabinoids have a different effect on the brain than other addictive drugs.
One synthetic cannibinoid has the same effect on part of the brain as antidepressants. © Punchstock
Eisch adds that much more work must be done before scientists can reach any definitive conclusions about the benefits and costs of marijuana. First and foremost, researchers need to establish that THC has the same positive effects as the synthetic HU210. Then they must develop more sophisticated experiments to firm up the correlation between neuron growth in the hippocampus and emotional balance.
Most addictive drugs inhibit the growth of new brain cells. But injections of a cannabis-like chemical seem to have the opposite effect in mice, according to new research. Experts say that the results, if borne out by further studies, could have far-reaching implications for addiction research and the application of marijuana in medicine.
Neuropsychologist Xia Zhang and a team of researchers based at the University of Saskatchewan in Saskatoon, Canada, aimed to find out just how marijuana-like drugs, known collectively as cannabinoids, act on the brain.
Jacobs says it could be that HU210 and THC do not have the same effect on cell growth. It could also be the case that cannabinoids behave differently in different rodent species – which leaves open the question of how they behave in humans.
When the rats who had received the cannabinoid were placed under stress, they showed fewer signs of anxiety and depression than rats who had not had the treatment. When neurogenesis was halted in these rats using X-rays, this effect disappeared, indicating that the new cell growth might be responsible for the behavioural changes.
In mammals, new nerve cells are constantly being produced in a part of the brain called the hippocampus, which is associated with learning, memory, anxiety and depression. Other recreational drugs, such as alcohol, nicotine and cocaine, have been shown to suppress this new growth. Xia Zhang of the University of Saskatchewan in Saskatoon, Canada, and colleagues decided to see what effects a synthetic cannabinoid called HU210 had on rats’ brains.
They found that giving rats high doses of HU210 twice a day for 10 days increased the rate of nerve cell formation, or neurogenesis, in the hippocampus by about 40%.
Just like Prozac?
In another study, Barry Jacobs, a neuroscientist at Princeton University, gave mice the natural cannabinoid found in marijuana, THC (D9-tetrahydrocannabinol)). But he says he detected no neurogenesis, no matter what dose he gave or the length of time he gave it for. He will present his results at the Society for Neuroscience meeting in Washington DC in November.
A synthetic chemical similar to the active ingredient in marijuana makes new cells grow in rat brains. What is more, in rats this cell growth appears to be linked with reducing anxiety and depression. The results suggest that marijuana, or its derivatives, could actually be good for the brain.
A previous study showed that the antidepressant fluoxetine (Prozac) also increases new cell growth, and the results indicated that it was this cell growth that caused Prozac’s anti-anxiety effect. Zhang wondered whether this was also the case for the cannabinoid, and so he tested the rats for behavioural changes.
Zhang says more research is needed before it is clear whether cannabinoids could some day be used to treat depression in humans.
The younger a person starts using, the greater the reduction of their brain size—the prefrontal cortex specifically). While there is still much to understand about the specific parts of the juvenile brain that are impacted and why, many other drug studies have shown that younger introduction to drug use can make individuals more prone to mental illness and addiction, in addition to cognitive impairment.
While weed doesn’t directly result in the death of the neurons the way that stress, head trauma, or other types of substances can, it can still go on to cause significant—and long-lasting—damage. This brain damage can lead to permanent side effects such as impaired memory, mental illness, and in the case of adolescents and their still-developing brains, a lower IQ.
Many mental illnesses are a result of either too much or too little dopamine in the brain. Marijuana has been found to result in lower dopamine activity in chronic users. This can cause psychotic symptoms similar to that of schizophrenia: anxiety, paranoia, and hallucinations. Known as cannabinoid-induced psychosis, it makes it difficult, if not impossible, to retain one’s grasp on reality and also represents a greater dysfunction with the brain’s processing that also severely impacts cognition. In other studies, student-age marijuana users experienced “slower processing speeds, poorer verbal learning and memory, and sequencing abilities”.
Numerous studies conducted over the past few decades have found that years of chronic cannabis use resulted in significant reductions in gray matter volume. Gray matter is the neuron-dense part of our brain, which is largely responsible for our capabilities to learn and otherwise function. One particular study found that heavy cannabis use resulted in shrinkage of hippocampus and amygdala parts of the brain which can significantly impact memory and learning.
4 Ways That Marijuana Affects Cognition
A New Zealand study involving over 1,000 teenagers had them take an IQ test at age 13 and then again at age 38 and also inquired as to their drug use habits. The study found that those who used marijuana at least four times a week experienced an average IQ drop of 8 points during this period. This experiment is the first of its kind to confirm that marijuana usage can directly contribute to loss of intelligence. The results also highlight the significance of frequency when it comes to the likelihood of severe or lasting side effects. However, there was one finding that overshadowed all the rest…
Table of Contents
Though marijuana may not be as overtly damaging as alcohol, meth, or cocaine (substances that drastically alter brain chemistry and uncoincidentally, are highly addictive), there are still plenty of undesirable cognitive side effects to be had.
How Marijuana Works
Any type of prolonged use of a psychoactive substance has the potential to cause neurological imbalances or impairment—and marijuana is no exception. The exact nature and extent of brain damage or other lasting effects can depend on a number of factors including:
What are the side effects that come to mind when you think of marijuana use? Most likely giggling, slowed speech and movements, and a sudden craving for snacks. This bumbling stereotype might lead you to believe that marijuana makes you dumber, but the scientific consensus seems to be that marijuana does not kill brain cells. This doesn’t mean that marijuana is harmless, however.