Cannabis appears to have a significant impact on the recognition and processing of human emotions like happiness, sadness and anger, according to research published in the journal PLOS One.
Scientists are only just starting to understand how cannabis affects the brain.
Cannabis consumption is known to cause immediate, residual and long-term changes in brain activity that can affect appetite and food intake, sleep patterns, executive function and emotional behavior.
Conflicting evidence has suggested that it can intensify both positive and negative mood states.
Lucy Troup, assistant professor of psychology at Colorado State University, and her graduate students wanted to look at how, if at all, cannabis use impacts a person's ability to process emotions.
For nearly 2 years, the team has been conducting experiments using an electroencephalogram (EEG) to measure the brain activities of about 70 volunteers.
All the participants identified themselves as chronic, moderate or non-users of cannabis. They were all confirmed to be legal users of marijuana under Colorado Amendment 64, either medical marijuana users aged 18 years and above, or as recreational users aged 21 years or older.
An EEG can record a wide variety of generalized brain activity. In this study, the researchers used it to measure the "P3 event-related potential" of the participants.
P3 refers to the electrical activity in the brain that is triggered by noticing something visually. P3 activity is known to be related to attention in emotional processing.
Marijuana use may reduce ability to empathize
While connected to an EEG, participants responded to faces wearing four separate expressions: neutral, happy, fearful and angry. The team collected P3 data that captured the reactions in certain parts of the brain when subjects focused on the face.
Cannabis users responded more intensely to faces showing negative expression, particularly angry ones, compared with controls. Conversely, their response to positive expressions, represented by happy faces, was smaller than that of the controls.
Little difference was observed between the reactions of cannabis users and non-users when asked to pay attention to and "explicitly" identify the emotion.
However, cannabis users scored lower in a task that asked them to focus on the sex of the face and then to identify the emotion. This suggests a reduced ability to "implicitly" identify emotions and to empathize on a deeper emotional level.
The researchers conclude that cannabis affects the brain's ability to process emotion, but that the brain may be able to counter the effects, depending on whether the emotions are explicitly or implicitly detected.
"We're not taking a pro or anti stance, but we just want to know, what does it do? It's really about making sense of it."
She explains that the aim of the emotion-processing paradigm was to see if the reactions in people who use cannabis would be different from those who do not.
Medical News Today recently reported that cannabis use could put young people more at risk of schizophrenia.