“A marijuana high can enhance core human mental abilities. It can help you to focus, to remember, to see new patterns, to imagine, to be creative, to introspect, to empathically understand others, and to come to deep insights.”
― Sebastian Marincolo

A study published in Psychology and Neuroscience proposed that, compared to nonusers, moderate cannabis users perform equally well on tests measuring decision making, impulsivity and executive function.

This research was carried out by Jonas Caio Costa Porfirio, Renata Maria Nogueira and Breno Corrêa Gomes from the Federal University of Pernambuco. 

Although cannabis is often associated with the feeling of euphoria, there are numerous other benefits to this drug. Some individuals use cannabis for the treatment of chronic pain, seizures and depression. Others report using cannabis to enhance concentration or help them connect with nature. 

Despite its many purposes and global popularity, there is still a widespread stigma against the use of this drug. Cannabis users are often stereotyped as unmotivated, lazy and inept. This stereotype exists, in part, because cannabis is thought of as a drug that makes users “dumber”. 

Knowing how cannabis actually affects your cognitive abilities is important for your health and is essential for reducing the spread of misinformation. This led the researchers to design a study examining the cognitive effects of cannabis use. 

The study & findings

The experiment consisted of undergraduate students, half of whom were moderate cannabis users while the other half were nonusers. The participants began by completing a series of questionnaires to ensure they didn’t suffer from cannabis dependence or any psychiatric disorders and didn’t frequently use other illicit drugs. Those who qualified for the study were asked to refrain from using cannabis for 24 hours. 

On the day of the experiment, participants completed five tasks to assess their decision-making ability, impulsivity and executive function (i.e., working memory, cognitive flexibility, and inhibitory control).

Working memory 

The first task, the Digit Span test, was designed to examine working memory. Participants were instructed to read a sequence of numbers and asked to repeat the same sequence in order (forward span) and in reverse order (backward span).  

Cognitive flexibility

To test cognitive flexibility, participants completed the Trail Making test. In trail A, participants were instructed to draw lines connecting numbers circled on a page in sequence as quickly as possible. In trail B, participants were asked to alternate between numbers and letters. Participants were scored based on the time it took to complete the task and the number of errors they made. 

Inhibitory control

The researchers tested inhibitory control with the Victoria Stroop test. The Victoria version includes three cards, 1 (color), 2 (word), 3(color-word). The first card contains pink, green, blue, and brown rectangles and the colors must be named as quickly as possible. The second card contains the words EACH, TODAY, NEVER and EVERYTHING printed in the same colors. The participant must simply read the words as quickly as possible. 

 The third card lists the names of four colors, printed in a color that is incompatible with the written word itself. Participants must name the color of the word, not the written word itself (e.g., if the word BLUE was written in red ink, the answer is red, not blue)

Decision making

To evaluate decision making, participants completed the Iowa Gambling Task. In this task, participants had to choose one card at a time from the four available decks (A, B, C, or D). Each card would cause them to either win or lose a certain amount of money. 

The cards in decks A and B contained high immediate gain, but also incurred higher loss in the long run, making them the disadvantageous decks. In contrast, decks C and D yielded lower gains, but in the long run incurred smaller losses, making them the advantageous decks. Each participant’s net score was measured (the number of cards selected from the advantageous decks minus the disadvantageous decks). 

Impulsivity

Traits of impulsivity were measured with the Barratt Impulsive Scale. This questionnaire contains 30 statements such as “I make-up my mind quickly.” Participants were instructed to respond between 1 (rarely/never) to 4 (almost always/always). The scores range from 30 to 120, with higher scores indicating the presence of impulsive behavior. 

After completing all five tasks, the researchers examined the results. In contrast to previous research, there wasn’t a significant difference in the performance of cannabis users compared to nonusers. That is, moderate cannabis use didn’t negatively (or positively) impact the participants' working memory, cognitive flexibility, inhibitory control, decision making or impulsivity.