Marijuana: Its Long-Term Effects on the Brain

Marijuana use is a widespread practice today, being one of the most consumed drugs.

While socially has been seen as a soft drug comparable to alcohol and with relatively little risk in its use (in fact it has interesting properties that make it very useful at a medicinal level in different diseases and disorders), the frequent use of this drug can have relevant long-term negative effects, especially in relation to the brain and its structure.

Of course, that does not mean it is a very dangerous drug comparable, for example, to the heroin. However, the defense that has been made about the supposedly innocuous nature of its consumption is difficult to defend today, as we will see.

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What is marijuana?

Marijuana it is one of the many ways in which cannabis is consumed, specifically the one that uses chopped and shredded leaves and stems of the plant. This substance has psychoactive properties that have been known since ancient times, having been used medicinally and recreationally since then by different peoples. Today its consumption is widely spread worldwide, especially for recreational and recreational purposes, and it is even legalized in some places under certain conditions.

It is a substance whose initial effects are slightly stimulating and euphoric, to go on to induce states of physical and mental relaxation. It causes a decrease in the level of tension and pain, increases the feeling of hunger and reduces and slows down motor movement. It is also effective as an antiemetic and anticonvulsant.

The effects of this product are well known when it comes to the short term. However, there is more discussion regarding its long-term effects of marijuana, with often contradictory results depending on the type of study that has been carried out. Despite this, evidence today suggests that its regular use causes brain health to wear out more than it should over time.

Long-term effects of marijuana

Although cannabis, especially in its form of marijuana, is a widely known substance, studies regarding its effects have always been surrounded by great controversy. A large amount of research has been carried out in this regard, in some cases with unclear results, on the results of its consumption. However, different studies have shown that its consumption can cause long-term effects on the brain and behavior.

It is important to bear in mind that we are talking about cases in which consumption is carried out frequently over time. The effects in question depend on the age and the moment of neurodevelopment in which consumption begins, as well as the time during which said consumption has taken place.

1. Orbitofrontal cortex reduction

One of the results that the research has reflected is that the continued use of marijuana causes an obvious reduction in gray matter, especially in the orbitofrontal cortex. This also means less long-term ability to perform tasks that depend on this area, such as impulse control or planning.

2. Increases neural connectivity

Despite the above, many habitual users of this substance show apparently normal behavior after many years using marijuana. The reason for this is that, according to other studies, despite the reduction of gray matter in the brain, connectivity between the remaining neurons is increased, so that this loss is compensated in a certain way.

That is, although in normal conditions an increase in the connectivity of neurons would be good news, in this case it is the result of many neurons dying, making those that remain have to "work" more; It is a brain mechanism to try to make up for the loss of thickness of the cortex. In addition, this increase in connections is less and less as consumption time increases.

3. Decreased performance and memory capacity

Different studies carried out show that habitual cannabis use can lead to a decrease in capacity in the long run intellectual performance of the subjects, having a lower performance and results in different tests than in comparison with an individual did not consumer. However, in this type of cognitive competences many contradictory results have been found, which means that this phenomenon may not be significant.

What there is solid evidence for is that marijuana use produces long-term problems in various types of memory. For example, these alterations result in greater difficulty in transferring the contents of short-term memory to long-term memory.

It is important to note that these effects are especially noticeable in people who consume throughout their process of development, that is, adolescents, due to the structural modification of the brain that the consumption of cannabis. In adults already formed who begin to consume this decrease is less.

• Related article: "Types of memory: how does the human brain store memories?"

4. Does it promote hippocampal neurogenesis?

One of the most widely publicized positive effects of cannabis is the ability to promote formation of new neurons in the hippocampus, region of the brain involved in the processing of memories. In fact, one of the medicinal applications of cannabis takes advantage of this factor and the fact that it reduces the formation of betaamyloid protein in order to help fight certain disorders that cause progressive degeneration of the hippocampus.

However, this has recently been seen to occur in laboratory rats used for experiments, but not in humans: in our case, the birth of new hippocampal neurons is practically non-existent in adults.

• Related article: "Hippocampus: functions and structure of the memory organ"

5. It can produce psychotic outbreaks

While it does not occur in all cases, some cannabis variants can facilitate the appearance of psychotic breakouts in people with a genetic predisposition to them, especially when consumption begins in adolescence. This is because early consumption hinders the correct neuronal maturation of the connection between prefrontal and limbic system, which facilitates the appearance of hallucinations and makes control and behavioral inhibition difficult. In some cases it can potentiate the expression of the schizophrenia.

• Related article: "Research reveals why marijuana can cause schizophrenia"

6. Decreased impulse control

Another of the effects observed and directly linked to the reduction of gray matter in the frontal cortex is decreased impulse control. The ability to inhibit behavior is linked to specific parts of this lobe, which is responsible for counteracting the power of the limbic system, related to emotions and the appearance of desires.

Bibliographic references:

• Colizzi, M., Iyegbe, C., Powell, J., Blasi, G., Bertolino, A., Murray, R. M. and Di Forti M. (2015). Interaction between DRD2 and AKT1 genetic variations on risk of psychosis in cannabis users: a case – control study. npj Schizophrenia 1, 15025 doi: 10.1038 / npjschz.2015.25.
• Dennis, C. V., Suh, L. S., Rodriguez, M. L., Krill, J. J. and Sutherland, G. T. (2016). Human adult neurogenesis across the ages: An immunohistochemical study. Neurophatology and Applied Neurobiology, 42 (7); pp. 621 - 638.

• Filbey, F. M.; Aslan, S.; Calhoun, V.D.; Spence, Jeffrey S.; Damaraju, E.; Caprihan, A. & Segall, J. (2014). Long-term effects of marijuana use on the brain. PNAS. vol. 11;47. Center of BrainHealth. University of Texas.

• Jiang, W.; Zhang, Y.; Xiao, L.; Van Cleemput, J. M.; Ji, S.P.; Bai, G. & Zhang, X. (2005). J.Clin. Invest. 115 (11); pp. 3104 - 3116.

• Volkow, N. D., Baler, R. D., Compton, W. M., Weiss, S. R. B. (2014). Adverse Health Effects of Marijuana Use. The New England Journal of Medicine, 370, pp. 2219 - 2227.