Humans have been using cannabis for thousands of years, and it is still one of the most popular substances today. It is also permitted to prescribe or consume in several countries, with effects such as sensations of joy and relaxation.

But what effect does the substance have on the mind? Studies published in The Journal of Psychopharmacology, Neuropsychopharmacology and the International Journal of Neuropsychopharmacology have shown that it can affect a number of cognitive and psychological processes.

According to the United Nations Office on Drugs and Crime, roughly 192 million persons aged 15 to 64 used cannabis recreationally in 2018. Young folks are particularly enthusiastic, with 35 percent of those aged 18 to 25 using it, compared to only 10 percent of those aged 26 and more.

This suggests that the primary users are teenagers and young adults, whose brains are still developing. They may thus be more vulnerable to the long-term consequences of cannabis usage on the brain.

Tetrahydrocannabinol (THC) is the principal psychoactive component of cannabis. It works by interacting with the brain’s “endocannabinoid system,” which consists of receptors that react to the active compounds of cannabis. The prefrontal and limbic parts of the brain, which are involved in reward and motivation, are heavily packed with cannabis receptors. They control the signaling of the brain neurotransmitters dopamine, glutamate, and gamma-aminobutyric acid (GABA).

Dopamine is known to play a role in motivation, reward, and learning. GABA and glutamate are involved in cognitive functions such as learning and memory.

Effects on the mind

Cannabis use can have a negative impact on cognition, especially in people with cannabis use disorder. This is marked by a strong desire to use the drug and disruptions in daily activities such as work or school. Approximately 10 percent of cannabis users are thought to fit the diagnostic criteria for this disease.

In one study, researchers compared the cognition of 39 patients with the disease (who were instructed to be clean on the day of testing) to that of 20 people who never or seldom used cannabis. They discovered that those with the disorder performed much worse on memory tests from the Cambridge Neuropsychological Test Automated Battery (CANTAB) than people who had never or only sometimes smoked cannabis. It also harmed their “executive functions,” which include mental skills like flexible thinking. This effect appeared to be related to the age at which patients began taking the medicine — the younger they were, the worse their executive function was.

Mild cannabis users have also been found to have cognitive deficits. These users are more likely to take risks and have difficulty planning than others.

Despite the fact that the majority of studies have been done on men, there has been evidence of gender variations in the effects of cannabis on cognition. Female cannabis users exhibited more difficulty with attention and executive functions than male cannabis users, according to these findings. When age, IQ, alcohol and nicotine usage, mood and anxiety symptoms, emotional stability, and impulsive behavior were all controlled for, the sex effects remained.

Motivation, reward, and mental health

Marijuana usage can also alter our emotions, which in turn might influence our thinking. Previous study has revealed that when we consume cannabis, reward and motivation, as well as the brain circuits involved in these activities, can be disturbed. This may have an impact on our academic or professional success since it makes us feel less driven to work hard and less rewarded when we succeed.

In a recent study, participants sat in a scanner and looked at orange or blue squares while doing a brain imaging task. If the participant responded to the orange squares, they would receive a monetary reward after a wait. They were able to explore how the brain responds to rewards using this setup. They concentrated on the ventral striatum, which is an important aspect of the brain’s reward system. They discovered that cannabis has only minor effects on the brain’s reward system, with no direct effects on the ventral striatum. The participants in this study, on the other hand, were moderate cannabis users. Cannabis users with more severe and chronic usage, as demonstrated in cannabis use disorder, may have stronger effects.

There’s also proof that cannabis can cause mental health issues. It has been linked to greater levels of “anhedonia” – the inability to perceive pleasure – in adolescents. This effect was notably noticeable during the COVID-19 pandemic lockdowns, which was surprising.

It has also been claimed that cannabis use during adolescence is a risk factor for psychotic episodes and schizophrenia. According to one study, cannabis usage raises the likelihood of psychotic symptoms in young people by a small amount, but it has a significantly higher effect on those who are predisposed to psychosis (scoring highly on a symptom checklist of paranoid ideas and psychoticism).

In a study of 2,437 adolescents and young adults (aged 14 to 24 years), the authors discovered a six-percentage-point increase in the incidence of psychotic symptoms in cannabis users who did not have a genetic predisposition to psychosis (from 15 percent to 21 percent, respectively). However, in cannabis users with a psychotic predisposition, the probability of psychotic symptoms increased by 26 percent, from 25 percent to 51 percent.

We don’t know why cannabis is associated to psychotic episodes, although dopamine and glutamate are thought to have a role in the neurobiology of these disorders.

Another study of 780 adolescents found that a brain region called the “uncus” was linked to the link between cannabis usage and psychotic events. It contains a large number of cannabinoid receptors and is located within the parahippocampus (related in memory) and olfactory bulb (engaged in smell processing). It has also been linked to schizophrenia and psychotic experiences in the past.

Cannabis’ cognitive and psychological effects are likely to be influenced by dosage (frequency, duration, and potency), sex, genetic vulnerabilities, and onset age. However, we must evaluate if these impacts are transient or persistent. According to one paper that summarized numerous studies, the effects of modest cannabis usage may fade following periods of abstinence.

Even if that’s the case, it’s important to examine the long-term impacts of cannabis usage on our minds, especially in young people whose brains are still developing.

Image Credit: Getty

You were reading: Does that mean marijuana makes our brain age faster?