How marijuana affects our cognition and psychology, according to new studies

THE cannabis it’s been used by humans for thousands of years — and it’s one of the most popular drugs today. With effects such as a feeling of joy and relaxation, it can also be legally prescribed or used in several countries.

But how does drug use affect the mind? In three recent studies published in The Journal of Psychopharmacology, Neuropsychopharmacology and the International Journal of Neuropsychopharmacology, we show that it can influence various cognitive and psychological processes.

The United Nations Office on Drugs and Crime reported that in 2018, approximately 192 million people worldwide aged between 15 and 64 used cannabis for recreational purposes.

Young adults are particularly interested, with 35% of 18-25 year olds using it, compared to just 10% of those over 26.

This indicates that the main users are teenagers and young adults, whose brains are still developing.

They may therefore be particularly vulnerable to the effects of using cannabis in the brain in the long run.

Tetrahydrocannabinol (THC) is the main psychoactive compound in cannabis. It works on the brain’s “endocannabinoid system”, which are receptors that respond to the chemical components of the brain. cannabis.

The receivers of cannabis they are densely populated in the prefrontal and limbic areas of the brain involved in reward and motivation. They regulate the signaling of the brain chemicals dopamine, gamma-aminobutyric acid (GABA) and glutamate.

We know that dopamine is involved in motivation, reward and learning. GABA and glutamate play a role in cognitive processes, including learning and memory.

Cognitive effects

The use of cannabis can affect cognition, especially in those with drug use disorder. cannabis. This is characterized by the persistent desire to use the drug and the interruption of daily activities, such as work or study.

It is estimated that approximately 10% of users of cannabis meet the diagnostic criteria for this disorder.

In our research, we tested the cognition of 39 people with the disorder (required not to use the drug on test day) and compared it with that of 20 people who never or rarely used the drug. cannabis.

We showed that participants with the condition performed significantly worse on the Cambridge Neuropsychological Test Automated Battery (CAMbridge Neuropsychological Test Automated Battery) memory tests, compared to control subjects, who never or very rarely used cannabis.

It also negatively affected their “executive functions”, which are mental processes, including flexible thinking.

This effect appeared to be linked to the age at which people started using the drug — the younger they were, the more impaired their executive functions were.

Cognitive impairments were also observed in light users of cannabis. These users tend to make riskier decisions than others and have more problems with planning.

Although most studies have been carried out in men, there is evidence of differences between the sexes with regard to the effects of drug use. cannabis in cognition.

We show that while the memory of male users of cannabis was weaker to visually recognize things, female users had more problems related to attention and executive functions.

These sex-attributed effects persisted when controlling for age; IQ; use of alcohol and nicotine; mood and anxiety symptoms; emotional stability; and impulsive behavior.

Reward, motivation and mental health

The use of cannabis it can also affect how we feel — further influencing our thinking.

For example, some previous research has suggested that reward and motivation—along with the brain circuits involved in these processes—may be affected when we use Çpineapple.

This can get in the way of our performance at school or work as it can make us feel less motivated to work hard and less rewarded when we do well.

In our recent study, we used a brain imaging task, in which participants were placed in an MRI scanner and viewed either orange or blue squares.

The orange squares would lead to a monetary reward, after an interval, if the participant gave an answer.

This setup helped us investigate how the brain responds to rewards. We particularly focused on the ventral striatum, which is a key region in the brain’s reward system.

We found that the effects on the reward system in the brain were subtle, with no direct effects of cannabis in the ventral striatum.

However, the participants in our study were moderate users of cannabis.

The effects may be more pronounced in users of cannabis who make more intense and chronic use, as observed in substance use disorder. cannabis.

There is also evidence that the cannabis can lead to mental health problems.

We have shown that it is related to greater “anhedonia”—the inability to experience pleasure—in adolescents. Interestingly, this effect was particularly pronounced during the Covid-19 pandemic lockdowns.

The use of cannabis during adolescence has also been reported as a risk factor for developing psychotic experiences, as well as schizophrenia.

One study showed that the use of cannabis moderately increases the risk of psychotic symptoms in young people, but has a much stronger effect on those with a predisposition to psychosis (scores high on a symptom list of paranoid ideas and psychoticism).

When evaluating 2,437 adolescents and young adults (14-24 years), the authors observed a six percentage point increased risk—from 15% to 21%—of psychotic symptoms in drug users. cannabis no predisposition to psychosis.

But there was a 26-point increase in risk — from 25% to 51% — of psychotic symptoms in drug users. cannabis predisposed to psychosis.

We don’t really know why the cannabis is linked to psychotic episodes, but hypotheses suggest that dopamine and glutamate may be important in the neurobiology of these conditions.

Another study with 780 adolescents suggested that the association between the use of cannabis and psychotic experiences was also linked to a region of the brain called “uncus”.

It is found within the parahippocampus (involved in memory) and in the olfactory bulb (involved in processing smells) and has a large number of cannabinoid receptors. It has also been associated with schizophrenia and psychotic experiences.

The cognitive and psychological effects of using cannabis are likely to some extent dependent on dosage (frequency, duration, and strength), sex, genetic vulnerabilities, and age of onset.

But we need to determine whether these effects are temporary or permanent.

An article summarizing several studies suggested that in the case of light use of cannabisthe effects may diminish after periods of abstinence.

But even if this is the case, it is worth considering the effects that prolonged use of cannabis may have on our minds—especially in young people whose brains are still developing.

_{Barbara Jacquelyn Sahakian is a professor of clinical neuropsychology at the University of Cambridge, UK.}

_{Christelle Langley is a postdoctoral research associate in cognitive neuroscience at the University of Cambridge.}

_{Martine Skumlien is a doctoral student in psychiatry at the University of Cambridge.}

_{Tianye Jia is a professor of population neuroscience at Fudan University in China.}

_{This article was originally published on the academic news site The Conversation and republished here under a Creative Commons license. Read the original version here (in English).}