Editor's comment: "Duh!"
Smoking cannabis can make people less willing to work for money while "high", finds a study.
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The research, published in Psychopharmacology, demonstrated the short-term effects of cannabis on motivation in humans and tested motivation in people who were addicted to cannabis but not high during the test.
It was found that their motivation levels were no different to volunteers in the control group.
The researchers compared people dependent on cannabis to similar controls, when neither group was intoxicated and did not find a difference in motivation.
This tentatively suggests that long-term cannabis use may not result in residual motivation problems when people stop using it. However, longitudinal research is needed to provide more conclusive evidence.
For this study, 57 volunteers were involved, which consisted of two separate studies. The first involved 17 adult volunteers who used cannabis occasionally.
Straight after, they completed a task designed to measure their motivation for earning money. This was a real-life task as the volunteers were given money they had earned at the end of the experiment.
In each trial of the task, volunteers could choose whether to complete low or high effort tasks to win varying sums of money. The low-effort option involved pressing the spacebar key with the little finger of their non-dominant hand 30 times in 7 seconds and the high-effort option involved 100 space bar presses in 21 seconds. The reward was higher for high-effort option.
"Repeatedly pressing keys with a single finger isn't difficult but it takes a reasonable amount of effort, making it a useful test of motivation. We found that people on cannabis were significantly less likely to choose the high-effort option," said Will Lawn, researcher at the University College of London.
In the second study, 20 persons addicted to cannabis were matched with 20 control participants who reported the same levels of non-cannabis drug use. Participants were not allowed to consume alcohol or drugs, other than tobacco or coffee, for 12 hours before the study.
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They were then asked to perform the same motivation task as participants in the first study. The results showed that cannabis-dependent volunteers were no less motivated than the control group.