In the second episode of The Queen's Gambit, from Wikipedia's summary:
After her overdose, Beth is forbidden to play chess. Time passes and Beth is adopted as a teenager by suburban couple Alma and Allston Wheatley. Allston is emotionally distant and frequently leaves for "business trips"; it soon becomes clear that their marriage is not a happy one. At her new high school, Beth is bullied by the popular girls from the "Apple Pi Club" for her drab clothes. Beth discovers her adoptive mother is taking the same tranquilizer pills that she was given at the orphanage and secretly steals some for herself, allowing her to play mental chess again. She also steals a chess magazine and learns about the upcoming Kentucky State Championship. She writes to Mr. Shaibel, who sends her the money for the entrance fee. As she cruises through her games, she develops a crush on one of her opponents, a young man named Townes. After the second day of the tournament, during which her periods start, Beth comes home to find that Allston has deserted them. Beth fears that she will be sent back to the orphanage, but Alma tells her they will lie so she can stay. During her final game of the tournament against Harry Beltik, the highest-ranked player, Beth becomes flustered and runs to the restroom, where she takes a tranquilizer pill, then wins the game. Upon learning of the prize money on offer in a tournament in Cincinnati, Alma hatches a plan for the two women to support themselves.
This description makes it sound like tranquilizers are a performance-enhancing drug. Does taking tranquilizers count as cheating in chess? I'm aware that there is some kind of anti-doping tests in chess, but I do not know what the tests test for.