Lysergic acid diethylamide ( or or ), abbreviated LSD or LSD-25, also known as lysergide (INN) and colloquially as acid, is a psychedelic drug of the ergoline family, well known for its psychological effects—which can include altered thinking processes, closed- and open-eye visuals, synesthesia, an altered sense of time, and spiritual experiences—as well as for its key role in 1960s counterculture. It is used mainly as an entheogen and recreational drug. LSD is not addictive. However, acute adverse psychiatric reactions such as anxiety, paranoia, and delusions are possible.