CHICAGO, NOV. 24 -- Drinking the liqueur absinthe and possibly eating paint may have contributed to Vincent van Gogh's insanity and could provide an explanation for the artist's bizarre behavior, a scientist said today.

Wilfred Niels Arnold, a professor of biochemistry at the University of Kansas Medical Center in Kansas City, told the medical detective story in the Journal of the American Medical Association.

Studying the postimpressionist painter's letters and other records from van Gogh's short life (1853-1890), Arnold and others found indications that in late life van Gogh was a heavy drinker of absinthe, a strong, emerald green liqueur flavored with wormwood and other herbs. Another painter, Henri de Toulouse-Lautrec, may have introduced van Gogh to the bitter drink.

While other researchers have speculated absinthe may have aggravated a genetic disposition to mental illness that ran in van Gogh's family, biochemist Arnold reviewed the chemical structure of a compound in wormwood extract and related compounds.

This gave him new evidence that an affinity for terpenes, a common class of compounds in aromatic plants, may have caused the painter's fits and hallucinations, and possibly led to a pica, or "depraved appetite" for nonfood items like paint.

Absinthe was banned in France in 1922, but consumption of it was common during van Gogh's life "and four times the national average in Arles" and St. Re'my, where the painter spent much of his later life.

Arnold said wormwood contains thujone, a terpene that can cause stomach problems -- similar to those van Gogh complained of -- and nervous system problems like mood swings, convulsions, permanent brain damage and even death.

"In the last 18 months of his life, when van Gogh experienced at least four fits with hallucinations resembling those described by absinthe drinkers, he was exposing himself to increasing amounts of thujone," Arnold wrote.

Thujone can have especially strong effects in concert with nicotine, and van Gogh acknowledged he smoked too much.

Bromides, medications containing the element bromine, counter convulsions caused by thujone, and were given as treatment to van Gogh, along with orders to abstain from absinthe.

Along with overindulgence in absinthe, van Gogh did some very peculiar things Arnold believes may be linked to pinene and camphor, two terpenes that are similar to thujone.

In one letter to his brother, van Gogh said he fought "insomnia with a very, very strong dose of camphor in my pillow and mattress." Arnold said camphor has the same effects as thujone on the body.

Just before he was committed to an asylum, van Gogh had to be restrained from drinking "about a quart of essence of turpentine from the bottle." Others reported van Gogh ate paint containing turpentine, which contains pinene.

"Vincent developed an affinity for chemicals of this type," Arnold said in an interview. "This working hypothesis removes some of these episodes in van Gogh's later life from the realm of curious absurdities ... People have said eating paint is as absurd as eating an ashtray, but it's not if the guy had a strong affinity for terpenes."