Vincent van Gogh likely suffered from "delirium" caused by alcohol withdrawal, according to a new study of the artist's psychiatric illnesses.
In order to investigate the artist's possible psychiatric disorders, experts interviewed art historians familiar with 902 letters from the artist -- 820 to his brother, Theo -- and studied medical records made by doctors who treated him.
The Dutch master, who produced some 900 paintings during his lifetime, died by suicide in 1890 at the age of 37 following years of mental illness.
He is thought to have suffered from a combination of bipolar and borderline personality disorder, though these illnesses were never diagnosed.
Researchers from The University Medical Center Groningen, in the Netherlands, say that they believe Van Gogh experienced two brief psychotic episodes, presumed to be delirium caused by alcohol withdrawal, following his admission to hospital after cutting off his own ear with a razor in 1888.
The experts believe the delirium was caused after the artist was forced to stop drinking alcohol after being admitted to hospital.
Researchers say that the Dutch master experienced several severe depressive episodes in the last year of his life -- at least one with psychotic features.
The team also ruled out some theories surrounding Van Gogh's suspected illnesses, finding notions that Van Gogh suffered from schizophrenia, the rare metabolic disease porphyria and gas poisoning from carbon monoxide "highly improbable."
However, experts say the theory that Van Gogh suffered from epilepsy, a diagnosis established by his own doctors, remains "open for discussion."
In the study, published Monday in the International Journal of Bipolar Disorders, researchers say that the artist's likely "masked epilepsy," also known as "focal epilepsy," could have led to differing manifestations of anxiety, delusions and hallucinations.
In Van Gogh's case, it could have been caused as a result of brain damage linked to his alcohol abuse, malnutrition, poor sleep and mental exhaustion.
However, as examinations such as imaging techniques and EEG tests (electric signal tests) were not available, experts say it is difficult to say for sure if he suffered from epilepsy.
Researchers caution that as they did not interview the artist themselves, their conclusions should be treated with caution.
"We think we can safely rule out some previously suggested diagnoses and we are more or less certain about several illnesses that he suffered from, but we will never really know for sure," Willem Nolen, Emeritus Professor of Psychiatry who coordinated the research, said in a statement.
"And although Van Gogh's letters contain a lot of information, we must remember that he didn't write them to his doctors, but to his brother Theo and other family members and other relatives in order to inform them, to reassure them or to get something done. He might have downplayed or even embellished certain things. Therefore, our article certainly won't be the last on Van Gogh's illnesses," he added.