As a competitive antagonist of GABAA receptor, thujone alone is considered to be convulsant,[8] though by interfering with the inhibitory transmitter GABA, it may convey stimulating, mood-elevating effects at low doses.

Thujone is found in a number of plants, such as arborvitae (genus Thuja, hence the derivation of the name), Nootka cypress, some junipers, mugwort, oregano, common sage, tansy, and wormwood, most notably grand wormwood (Artemisia absinthium), usually as a mix of isomers in a 1:2 ratio.

[10] Quantitative 13C NMR spectroscopic analysis has demonstrated that the isoprene units used to form thujone in plants are derived from the methylerythritol phosphate pathway (MEP).

From (+)-sabinene (8), the proposed biosynthetic route to generate thujone follows a three-step pathway: (+)-sabinene is first oxidized to an isomer of (+)-sabinol (9-1, 9-2) by a cytochrome P450 enzyme, followed by conversion to (+)-sabinone (10) via a dehydrogenase.

By inhibiting GABA receptor activation, neurons may fire more easily, which can cause muscle spasms and convulsions.

[17] Pretreatment with GABA positive allosteric modulators like diazepam, phenobarbital, or 1 g/kg of ethanol protects against a lethal dose of 100 mg/kg.

[citation needed] Attention performance has been tested with low and high doses of thujone in alcohol.

Other thujone-containing plants such as the tree arborvitae (Thuja occidentalis) are used in herbal medicine, mainly for their alleged immune-system stimulating effects.

[24] GC–MS testing is important in this capacity because gas chromatography alone may record an inaccurately high reading of thujone as other compounds may interfere with and add to the apparent measured amount.

Based on this, absinthe, which contains a small amount of wormwood oil, was assumed to be more dangerous than ordinary alcohol.

[18] In light of modern evidence, these conclusions are questionable, as they are based on a poor understanding of other compounds and diseases,[26] and clouded by Magnan's belief that alcohol and absinthe were degenerating the French race.

[27] After absinthe was banned, research dropped off until the 1970s, when the British scientific journal Nature published an article comparing the molecular shape of thujone to tetrahydrocannabinol (THC), the primary psychoactive substance found in cannabis, and hypothesized it would act the same way on the brain, sparking the myth that thujone was a cannabinoid.