Category Archives: marijuana

Daily marijuana use has a measurable effect on the brain, a new study finds.

Teenagers who smoked marijuana daily for three years performed poorly on memory tasks and showed abnormal changes in brain structure, according to a Northwestern Medicine study. Researchers in Chicago observed the brains of teenagers who were heavy users of marijuana. In those individuals, memory-related structures in the brain appeared to shrink and collapse inward, possibly indicating a decrease in neurons.

These abnormalities were recorded two years after the teens stopped using marijuana, possibly indicating long-term effects, and look similar to schizophrenia-related brain abnormalities.

The brains were shaped more abnormally for individuals who began marijuana use at a younger age, according to the reports, which suggest that memory regions of the brain are more susceptible to the drug at earlier ages.

The research was published in the December issue of Schizophrenia Bulletin.

Smoking Weed = less Creativity

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 illusion18

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

Heavy marijuana use may harm the brain

New NIDA-funded research shows that heavy marijuana use (at least four times per week over the past six months) is linked to adverse changes in the function and structure of brain areas associated with reward, decision making, and motivation.  Heavy marijuana use can also enhance some brain circuits – possibly to compensate for reduced function in specific brain regions. This effect was more pronounced in those who started using at a young age, indicating that developing brains are particularly vulnerable to marijuana’s effects.

Illustration of a neuron cell

Although further long-term studies are needed to determine whether marijuana caused these effects, these scientific findings add to the growing literature showing that heavy marijuana use may harm the brain.

For a copy of the abstract (published online November 10), go to www.pnas.org/content/early/2014/11/05/1415297111.abstract.