Cannabis use can affect your ability to recognise emotion

Cannabis use can significantly affect your ability to recognise, process and empathise with human emotions like happiness, sadness and anger, a new study has found.
The study also suggests that the brain may be able to counteract these effects depending on whether the emotions are explicitly, or implicitly detected.
For nearly two years, researchers from Colorado State University in US conducted experiments using an electroencephalogram (EEG) to measure the brain activities of about 70 human subject volunteers. They all self-identified as chronic, moderate or non-users of cannabis.
In the experiments, participants 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 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 empathise with the emotions.

The findings suggest that the brain's ability to process emotion is affected by cannabis, but there may be some compensation that counteracts those differences, researchers said.
There was no difference between users and non-users when they are directed to a specific emotion. But on a deeper level of emotion processing - depicted by the ability to empathise - the response was reduced in cannabis users.
Researchers measured the "P3 event-related potential" of the subjects. EEGs can record a wide variety of generalised 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.
"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. That is how it all started," said Lucy Troup from Colorado State University.
The findings were published in the journal PLOS ONE.