Trance
A trance was an altered mental state that could be self-induced. One such state was the Dolbargy sleeping trance. ()

Vulcans were able to put themselves into a trance that relaxed their minds and bodies. According to Spock, they found it to be superior to vacations. In 2268, James T. Kirk suggested Spock could fake illness by putting himself in a trance for half an hour. This would provide an excuse for him and Doctor Leonard McCoy to be allowed to return to the  by the Kelvans. McCoy noted that the Vulcan's pulse was slow and barely registered. After ordering Christine Chapel to give Spock stokaline, McCoy explained that Spock had been suffering from a flare-up of Rigelian Kassaba fever. ()

In 2376, Seamus tried to send "Father Mulligan" into a hypnotic trance to get him to tell the truth about his nature. ()

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Psychological conditions
Sleep