People who use cocaine get less enjoyment out of social interactions and have less empathy for others, a new study indicates.

After cannabis, cocaine is the most frequently used illegal drug worldwide, including throughout Europe. It is already known that chronic users of the drug are more likely to have problems with memory, attention and concentration.

Studies have also suggested that their social skills suffer. Researchers in Switzerland decided to look into this further. They found that people who use cocaine are less empathetic overall - they have problems seeing things from other people's perspectives and even find it difficult recognising emotions in other people's voices.

Furthermore, these people tend to be less social in social interactions and have fewer social contacts. The less empathy they have for others, the smaller their social network tends to be.

"Cocaine users perceive social exchange as less positive and rewarding compared to people who do not use this stimulant," explained the researchers from the University of Zurich.

They suggest that these apparent changes in brain function may explain why people dependent on cocaine fail to stop using the drug even if they suffer severe social consequences, such as family problems, loss of a job and loss of friends.

The researchers added that people who are being treated for cocaine addiction should therefore be trained in social skills.

"Social skills, such as empathy, mental perspective taking and pro-social behavior, should be trained during the treatment of cocaine dependence to enhance the efficacy and sustainability of the treatment."

Details of these findings are published in the journal, Proceedings of the National Academy of Sciences.