One of the side effects that some cocaine users report are intense feelings of euphoria, which a new study has confirmed by showing that just a single dose of the drug can block the ability to recognize negative emotions like sadness and anger.

The findings were presented at the annual European College of Neuropsychopharmacology (ECNP) conference in Amsterdam. Researchers compiled data from 24 students, ages to 19 to 27, who admitted to using cocaine at a light or moderate level. They were given either 300 miligrams of oral cocaine or a placebo, then put through a series of tests an hour later that included biochemical tests and facial recognition tests to recognize emotions.

Those given the cocaine dose showed both an increased heart rate and levels of the stress hormone, cortisol. Those who were intoxicated with cocaine were also 10% worse than the placebo takers at recognizing negative emotions.

“This might hinder the ability to interact in social situations, but it may also help explain why cocaine users report higher levels of sociability when intoxicated,” said lead researcher Dr. Kim Kuypers of the Maastricht University in The Netherlands. “They can’t recognize the negative emotions.”

Dr. Michael Bloomfield of University College, London, noted that cocaine changes brain levels of dopamine and long-term users could have permanent damage to their perceptions of emotions. He said that more research needs to be conducted into whether cocaine users “feel like other people have more negative emotions [when they’re off the drug.]”

That suggestion could help explain the findings of a separate study from December 2013, which found that heavy cocaine users binge on the drug not to seek a high, but rather to avoid a low.

The research project, published in the journal Psychopharmacology, used lab rats to show that initial positive feelings associated with the drug were short-lived and “quickly replaced by negative emotional responses whenever drug levels begin to fall.”