People sometimes think that smoking cannabis makes them more creative. However, research by Leiden psychologists Lorenza Colzato and Mikael Kowal shows that the opposite is true.

Strong cannabis doesn’t work

The findings show that cannabis with a high concentration of the psychoactive ingredient THC does not improve creativity. Smokers who ingested a low dose of THC, or none at all (they were given a placebo), performed best in the thinking tasks that the test candidates had to carry out. A high dose of THC was actually shown to have a negative effect on the ability to quickly come up with as many solutions as possible to a given problem.

Increased creativity is an illusion

The research findings contradict the claims of people who say that their thinking changes and becomes more original after smoking a joint. There’s no sign of any increased creativity in their actual performance, according to Colzato. ‘The improved creativity that they believe they experience is an illusion.’

Too much cannabis is counterproductive

Colzato said, ‘If you want to overcome writer’s block or any other creative gap, lighting up a joint isn’t the best solution. Smoking several joints one after the other can even be counterproductive to creative thinking.’

The research method

Colzato and her PhD candidate Kowal were the first researchers to study the effects of cannabis use on creative thinking. For ethical reasons, only cannabis users were selected for this study. The test candidates were divided into three groups of 18. One group was given cannabis with a high THC content (22 mg), the second group was given a low dose (5.5 mg) and the third group was given a placebo. The high dose was equivalent to three joints and the low dose was equal to a single joint. Obviously, none of the test candidates knew what they were being given; the cannabis was administered via a vaporizer. The test candidates then had to carry out cognitive tasks that were testing for two types of creative thinking:

• Divergent thinking: generating rapid solutions for a given problem, such as: “Think of as many uses as you can for a pen?”
• Convergent thinking: Finding the only right answer to a question, such as: “What is the link between the words ‘time’, ‘hair’ and ‘stretching’. (The answer is ‘long’.)

Mikael A. Kowal, Arno Hazekamp, Lorenza S. Colzato, Henk van Steenbergen, Nic J. A. van der Wee, Jeffrey Durieux, Meriem Manai, Bernhard Hommel. Cannabis and creativity: highly potent cannabis impairs divergent thinking in regular cannabis users. Psychopharmacology, 2014; DOI: 10.1007/s00213-014-3749-1