Cannabis is the most widely produced and used illicit drug among humans and it is the third most commonly used controlled substance globally. Its popular use can be attributed to its immediate effect of a pleasant euphoria and a sense of relaxation, and to its less common effects like heightened sensory perception, feelings of joy, altered perception of time, and change in appetite higher than the usual, and in some countries, it is also legal to prescribe or consume the drug.
Years of research threw light upon its various effects on the brain and the body, particularly the respiratory and cardiovascular systems, risks during pregnancy, the cognitive effects, the associated mental illness, cannabis addiction, effects of high potency cannabis, on learning, and other life outcomes. Among these, the cognitive effects have gained attention by the Journal of Psychopharmacology, Neuropsychopharmacology, and the International Journal of Neuropsychopharmacology and they published three studies showing how cannabis can influence several cognitive and psychological processes.
According to the 2020 National Survey on Drug Use and Health, 17.9% (or about 49.6 million people) reported using cannabis in the past 12 months among people aged 12 or older in the United States, and according to the United Nations Office on Drugs and Crime, approximately 192 million people worldwide aged between 15 and 64 used cannabis recreationally in 2018.
Young adults are especially eager, as 2021 Monitoring the Future Survey reported that in 2021, an estimated 7.1% of 8 graders, 17.3% of 10 graders, and 30.5% of 12 graders used cannabis/hashish in the past 12 months and the United Nations Office on Drugs and Crime reported that in 2018, 35% of people worldwide between the ages of 18 and 25 take it, while only 10% of people over the age of 26 do, indicating that the principal consumers are adolescents and young adults whose brain is still developing. As a result, their vulnerability to the long-term consequences on the brain of using cannabis is exceptionally high.
The main psychoactive (mind-altering) chemical in cannabis is delta-9-tetrahydrocannabinol (THC), responsible for the majority of the intoxication effects. THC interacts with the receptors in the endocannabinoid system located in the prefrontal and limbic areas of the brain, which in turn respond to the chemical components of cannabis. The aforementioned areas of the brain are involved in reward and motivation, thus the effects of cannabis regulate the signaling of the brain chemicals dopamine, gamma-aminobutyric acid (GABA), and glutamate.
Motivation, reward, and learning are known to be affected by dopamine and cognitive processes such as learning and memory are influenced by GABA and glutamate.
Cognitive effects
Cannabis use disorder is defined as the continued use of cannabis despite clinically significant impairment in psychological, physical, or social functioning. Cannabis use can have an impact on cognition, particularly in individuals who suffer from this disorder. Approximately 10% of cannabis users are reported to meet the diagnostic criteria for this disorder.
The research studies tested and compared the cognition of 39 individuals with the disorder (clean on the day of testing) with that of 20 individuals who never or rarely used cannabis. It has been observed that the participants with the disorder performed significantly worse on memory tests from the Cambridge Neuropsychological Test Automated Battery (CANTAB) in comparison to the control group. The investigators also discovered that the executive functions, such as flexible thinking have been compromised. This negative effect can be attributed to the age at which the individuals started using the drug.
Whereas mild cannabis use can also cause cognitive impairments leading the users to take risky decisions and experience problems in planning. The research studies also highlight the gender variations in the effects of cannabis use on cognition despite most studies having been conducted on men. Male cannabis users’ experienced poorer memory for visually recognizing things, whereas female users experienced more difficulty with attention and executive functions.
Reward, motivation, and mental health
Using cannabis can influence our thinking and also affect how we feel. Previous research studies have revealed that when cannabis is consumed, reward and motivation, as well as the brain circuits involved in these processes can be disrupted affecting academic and professional performance.
A brain-imaging task where the participants were placed in a scanner and viewed orange or blue squares has been used. If the participant responded to the orange squares, they would receive a monetary reward after a delay thus investigating the brain’s response to rewards. The focus was particularly on the ventral striatum discovering that the effects on the brain’s reward system were minimal, with no direct effects of cannabis in the focused region, in the light of the moderate cannabis users.
The study also revealed that cannabis use can lead to higher anhedonia in adolescents, prominently noticeable during the COVID-19 pandemic lockdowns. Even moderate use in young people increases the likelihood of psychotic symptoms thus positing a risk factor for developing schizophrenia in adolescence given that a much stronger effect can be seen in those with a predisposition for psychosis (an increase in risk from 25% to 51%).
Though the reason behind the aetiology is unknown, it has been hypothesized that the neurobiology of psychotic conditions may be affected by dopamine and glutamate. A research study examining 780 teenagers also added to the fact that cannabis use and psychotic experiences are associated linking it to the brain region called “uncus” possessing a large number of cannabinoid receptors.
The frequency, duration, and strength of cannabis use, sex, genetic vulnerabilities, and age of onset are found to determine the cognitive and psychological effects be temporary or permanent. It’s crucial to examine the long-term impacts of cannabis use on our minds, especially in adolescents and young adults whose brains are still developing, even when it is considered that the effects of mild cannabis use may fade after periods of abstinence.
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