LSD Makes It Harder to Recognize Fear in Others

The last few years has seen a boom in research into the therapeutic effects of various psychedelic substances, which have been found to be effective in treating substance addiction, as well as depression and anxiety in terminally ill patients. Yet despite this boom in psychedelic medicine, no research had been published on how tripping effects emotions at a neurological level. This changes today with new research published in Nature's Translational Psychiatry, which shows that subjects taking LSD are less able to process frightening stimuli, an effect that could have big implications for using LSD to treat depression or anxiety.

The research was carried out by two medical institutions in Basel, Switzerland—the birthplace of LSD—on 20 healthy subjects between 25 and 58 years old. Of these subjects, about three-quarters had previously smoked weed, about a third had used MDMA, but only two had ever used a psychedelic.

Each test subject was dosed with 100 micrograms of LSD (a pretty standard dosage for the recreational user that produces "robust psychedelic effects") and two and a half hours later, were brought to have their brains imaged in a functional MRI (fMRI) machine. To judge the effects of LSD on processing fearful stimuli, the tripping subjects were shown 10 images of people's faces that bore either a fearful or neutral expression while they were in the fMRI machine.

According to the research, when subjects on LSD were exposed to images where the facial expression in the image expressed fear, this led to a low level of activity in the amygdala—the area of the brain believed to be responsible for processing emotions—as compared to those subjects who had been administered a placebo, who had significantly higher levels of activity in the amygdala. Moreover, the researchers found that "amygdala deactivation by LSD was associated with its acute subjective psychedelic effects." In other words, tripping significantly alters your ability to process emotions.

As the researchers noted, it could be argued that the decreased response to fearful facial expressions by subjects on LSD is due to visual impairment caused by the substance. However, in another study that gave subjects even higher dosages of LSD (between 100 and 200 micrograms), it was found that LSD specifically alters the ability to recognize fear, but not neutral, sad, or angry faces.

This new evidence that LSD tempers activity in the amygdala suggests it could have significant therapeutic use for those suffering from depression or anxiety, mental disorders that are associated with increased activity in that area of the brain and a bias toward negative stimuli.