SfN18: What are the neural risks and benefits of marijuana use? New studies shed light

Written by Zoe Campbell, Future Science Group

Marijuana is the most commonly used illicit drug in the USA and its use is expected to rise as it becomes legalized in more places. Research presented at SfN Neuroscience (3–7 November, San Diego, CA, USA) has brought to light insights into not only the risks of marijuana use but also its potential use as a therapeutic.
The findings presented by Maryland Psychiatric Resource Centre (BA, USA) have highlighted that prenatal exposure to THC (delta-9-tetrahydrocannabinolin; the psychoactive compound in marijuana) may have long-lasting effects in the brain, ones that may impair cognitive function and increase risk of psychiatric disorders later in life.

Many women believe marijuana is safe to use, but cannabinoids, such as THC, easily cross the placenta and disrupt fetal development, having an effect all the way into adulthood. There are currently no therapies to mitigate these effects.

As an early step toward identifying possible therapeutic options, researchers from Auburn University (AL, USA) investigated the mechanism by which prenatal cannabinoid exposure affects learning and memory in adolescent rats. Indeed, they showed cannabinoid exposure during pregnancy has the potential to disrupt the offspring’s learning and memory into adolescence.

For many, marijuana use begins as a teenager, which is a particularly vulnerable time as the brain is still developing. Researchers from Pontificia Universidad Católica de Chile (Santiago Metropolitan Region, Chile) set out to test this. José Fuentealba Evans (Pontificia Universidad Católica de Chile) senior author of the study explained: “The findings from this study provide new evidence that support the vulnerability of the adolescent period to exposure to cannabinoid.”

Marijuana use during adolescence may alter neuronal function in brain areas engaged in decision-making and self-control. A study from the University of Illinois (IL, USA) highlighted that at this time, the brain may be more vulnerable to long-term effects of drug use due to its ongoing development. It has the potential to affect regions such as the prefrontal cortex, responsible for high-level cognitive functions such as decision-making, planning and self-control.

Moving into adulthood, as many believe marijuana is safe to use, they will continue to use it regularly. However, research performed in adult mice by a team from the University of Lisbon (Portugal) showed long-term exposure could impair brain activity and neuronal connections involved in learning and memory.

A growing number of people are already turning to marijuana for the relief of symptoms of chronic diseases such as epilepsy and multiple sclerosis. Alzheimer’s disease currently affects around 5.4 million Americans. Cannabinoids, because of their similarity to endocannabinoids, have attracted interest as a possible therapeutic.

Endocannabinoids are naturally occurring compounds that play a role in several processes related to Alzheimer’s such as memory formation and muscle control. Hence, cannabinoids have the potential to reduce Alzheimer’s symptoms. Yvonne Bouter, University Medical Center Goettingen (Goettingen, Germany), senior author of this research stated: “Our results suggest that cannabinoids could present new therapeutic opportunities to prevent or slow down the cognitive decline in Alzheimer’s disease.”

Press conference moderator Michael Taaffe (Scripps Research Institute, CA, USA) and an expert in substance abuse research concluded: “Today’s findings lend new understanding of the complex effects that cannabis has on the brain. While it may have therapeutic potential in some situations, it is important to get a better understanding of the negative aspects as well, particularly for pregnant women, teens, and chronic users.”

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Sources:

  1. Beggiato S, Ferraro L, Schwarcz R. Prenatal THC exposure permanently disturbs kynurenic acid and glutamate levels and amplifies the responsivity to an acute kynurenine challenge in the rate prefrontal cortex. Programs and Abstracts of SfN Neuroscience 2018. San Diego, CA, USA, 3–7 November 2018 (Abstract 11263).
  2. Pinky PD, Bloemer j, Setti SE et al. Prenatal cannabinoid exposure results in learning and memory deficits in rodent adolescent offspring: elucidation of the mechanism and identification of a therapeutic target. Programs and Abstracts of SfN Neuroscience 2018. San Diego, CA, USA, 3–7 November 2018 (Abstract 13528).
  3. Pérez E, Grace AA, Andres ME, Fuentealba JA. Adolescent cannabinoid exposure increases nigrostriatal dopaminergic transmission. Programs and Abstracts of SfN Neuroscience 2018. San Diego, CA, USA, 3–7 November 2018 (Abstract 7114).
  4. Jacobs-Brichford E, Chen H, Lasek AW, Roitman JD. Effects of adolescent WIN exposure on perineuronal net emergence in PFC. Programs and Abstracts of SfN Neuroscience 2018. San Diego, CA, USA, 3–7 November 2018 (Abstract 13516).
  5. Mouro FM, Ribeiro J, Sebastiao A, Dawson N. Prolonged cannabinoid intake leads to memory impairment and to changes in brain metabolism and brain connectivity in mice. Programs and Abstracts of SfN Neuroscience 2018. San Diego, CA, USA, 3–7 November 2018 (Abstract 10629).
  6. Sichler ME, Bouter C, Wiltfang J, Low MJ, Bayer TA, Bouter Y. Effects of cannabidiol and tetrahydrocannabinol treatment on memory function, neuron loss and molecular signature in a mouse model of Alzheimer’s disease. Programs and Abstracts of SfN Neuroscience 2018. San Diego, CA, USA, 3–7 November 2018 (Abstract 8808).