Soulcatcher, maybe this makes it more clear:
Quoting from Wikipedia:
At the height of this popularity, absinthe was portrayed as a dangerously addictive, psychoactive drug; the chemical thujone was blamed for most of its deleterious effects. By 1915, it was banned in a number of European countries and the United States. Even though it was vilified, no evidence shows it to be any more dangerous or psychoactive than ordinary alcohol.
Thujone is a ketone and a monoterpene that exists in two stereoisomeric forms - (+)-3-thujone or ?-thujone and (-)-3-thujone or ?-thujone - and has a menthol odor. Even though it is best known for being a chemical in absinthe, recent tests show absinthe contains only small quantities. In the early 20th century thujone was blamed for the supposed dangerous and even hallucinatory effects of absinthe, however modern studies show these concerns to be unfounded. Thujone acts on the GABA receptors in the brain and does not cause hallucinations. In many countries the amount of thujone allowed in food or drink products is regulated.