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CBD Reduces Aggression (in Mice), Study Finds

By Leo Bear-McGuinness

Published: Jul 31, 2019   
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“Angry mice” become less aggressive when supplied with CBD, according to scientists who say the cannabis compound could help treat hostile humans.  

In a study published in Progress in Neuro-Psychopharmacology and Biological Psychiatry, Brazilian researchers isolated several male mice for 10 days and measured the incidents of “aggressive behavior” when intruders were introduced into their cages. 

They noted that the mice dosed with CBD displayed fewer and less aggressive attacks than the control group. 

CBD and creating-better-doses

Interpreting their results, the researchers believe the cannabis compound activated two receptors that coordinate behavior. 

“Our study shows that cannabidiol [CBD] can inhibit aggressiveness and that it does so by facilitating the activation of two receptors: the 5-HT1A receptor, responsible for the effects of the neurotransmitter serotonin, and the CB1 receptor, responsible for the effects of endocannabinoids,” said the study’s lead author, Francisco Silveira Guimarães, in a statement

Previous CBD studies have shown that the compound has anti-seizure properties, but little research has been done into its effect on aggression.

“Cannabidiol has been studied in various contexts for the past 20 years, but very little research has been done into its effects on aggressive behavior,” Guimarães said. 

To achieve the results, Guimarães and his team split the mice into five groups: four which were given varying strengths of CBD, and a control group that went without. After being isolated in a cage for days on end, the mice in this control group displayed the most aggressive behavior.

On average, these mice attacked an “intruder” within two minutes of being confronted and only stopped after 20-25 assaults. 

In contrast, the mice given the lowest CBD dose (equivalent to 5 milligrams per kilo) took twice as long to first attack intruders and the number of attacks fell by half.

And the second mouse group, supplied with 15 mg/kg of CBD, took even longer to attack an intruder. On average, the first attack happened after 11 minutes and was followed by only a few more attempts.  

However, the third and fourth groups, which received even higher doses of CBD (30 mg/kg and 60 mg/kg, respectively), attacked the intruders sooner – which may indicate that high doses of CBD can actually amplify aggression. But this relationship between behavior and dose was anticipated by the team. 

“This reduction in the effect of cannabidiol at higher doses was expected from the results of other studies,” said Guimarães. “In experiments to investigate its potential as an antidepressant, for example, higher doses led to lower effects after an initial gain. In our experiment, if we had tested 120 mg/kg on a group of mice, we might not have obtained any inhibition of the resident's aggressiveness at all.”

Expanding medication 

Currently, aggressive behavior is only explicitly listed as a medical marijuana qualifying condition in Delaware when associated with “self-injurious autism,” but Guimarães and his colleagues claim that many more patients struggling with aggression – especially those with psychiatric disorders – could benefit from a little CBD. 

However, as one of the first studies into CBD and aggression, further research in human subjects will be needed to properly validate Guimarães’ claims before more clinical decisions can be made. 

CBD-based medications have also been known to cause unwanted side effects, such as decreased appetite and diarrhea in child patients.   

Leo Bear-McGuinness

Science Writer & Editor

Leo joined Analytical Cannabis in 2019. From research to regulations and analysis to agriculture, his writing covers all the need-to-know news for the cannabis industry. He holds a Bachelor's in Biology from Newcastle University and a Master's in Science Communication from the University of Edinburgh.


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