Marijuana harms ability to recognize emotions
A study published in PLOS ONE suggests that marijuana harms the brains ability to recognize facial expressions and emotions.
Lucy Troup, assistant professor of psychology at Colorado State University, recruited 70 participants who are legally using marijuana.
Results show that cannabis users showed a greater response to faces showing negative expression, particularly angry, than controls. Conversely, cannabis users showed a smaller response to positive expressions – the happy faces – compared with controls.
Also, the participants were asked to pay attention to the emotion, and then identify it – to “explicitly” identify the emotion. In those cases, users and non-users of cannabis were virtually indistinguishable. But when asked to focus on the sex of the face, and later identify the emotion, 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 study seems to suggest that the brain’s ability to process emotion is affected by cannabis, but there may be some compensation that counteracts those differences. 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 – depicted by the ability to empathize – the response is reduced in cannabis users.
Specifically, Troup et al. measured the “P3 event-related potential” of the subjects. EEGs can record a wide variety of generalized brain activity. 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. P3 is the electrical activity in the brain triggered by visual attention – when one notices something. P3 activity is known to be related to attention in emotional processing.
Troup does not take a stand on medical marijuana, but just expressed interest in learning how it affects 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,” Troup said.
