COLORADO, USA, Monday March 7, 2016 – A study published last week in the journal PLOS ONE suggests that cannabis significantly affects users’ ability to recognize, process and empathize with human emotions like happiness, sadness and anger.
The study was led by Lucy Troup, assistant professor of psychology at Colorado State University, who has long been fascinated by the psychology of drugs and addiction.
Dr Troup’s interest in cannabis (marijuana) was piqued by Colorado’s passage of Amendment 64, legalising the drug, and the many conflicting studies of the herb’s long and short-term effects on the brain.
“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 said.
Troup and her graduate students have been conducting experiments for almost two years using an electroencephalogram (EEG) to measure the brain activities of about 70 volunteers who self-identified as chronic, moderate or non-users of cannabis.
These participants were all vetted as legal users of marijuana under Colorado Amendment 64, and were either medical marijuana users 18 or older, or recreational users 21 or older.
In the experiments, the volunteers connected to an EEG were asked to view faces depicting four separate expressions: neutral, happy, fearful and angry.
Cannabis users showed a greater response to faces showing negative expressions, particularly anger, than controls.
Conversely, the cannabis users showed a lesser response to the positive expressions of the happy faces compared with controls.
The volunteers were also asked to concentrate on an emotion and then identify it. In those cases, users and non-users of cannabis were virtually indistinguishable.
When asked to focus on the gender of the face, and later identify the emotion, however, cannabis users scored much lower than non-users. This signified a depressed ability to “implicitly” identify emotions. Cannabis users were also less able to empathize with the emotions.
The research suggests that there’s no difference between users and non-users when they’re directed to a specific emotion. But on a deeper level of emotion processing, shown in the ability to empathize, the response is reduced in cannabis users.
Troup and her team measured the “P3 event-related potential” of the subjects. P3 is the electrical activity in the brain triggered when one notices something. P3 activity is known to be related to attention in emotional processing.
In this case, they focused on what happens in certain parts of the brain when subjects were shown a face – the face being the event.
“We tried to see if our simple emotion-processing paradigm could be applied to people who use cannabis, because we wanted to see if there was a difference,” Troup said. “That’s how it all started.”
Dr Troup is leading a second EEG study focusing on the effects of cannabis on such mood disorders as anxiety and depression.
A member of her team is also investigating the effect of cannabis on learning.