Chronic cannabis use can lead to severe vomiting sickness.

Huh, and all this time I thought it was the Phish music that was making me puke. From EurekAlert:

This obscure clinical manifestation of severe vomiting sickness due to chronic abuse of marijuana, recognized by Dr. Sontineni and his colleagues at the Creighton University of Omaha, NE, was published on March 14, 2009 World Journal of Gastroenterology.

Recent research into the neurobiology of cannabis has led to the identification of different receptor types including two specific types that mediate neuropsychiatric and immunologic effects.

According to Dr. Sontineni, doctors and health care workers currently under recognize the syndrome leading to delayed diagnosis and expensive diagnostic investigations. Increasing consistent use of marijuana among United States populations, particularly young people, over several years will see a steady rise in the number of cases diagnosed each year.

The syndrome was first recognized in Australia around the Adelaide hills. The exact mechanism leading to generation of these symptoms, why it appears only after several years of marijuana abuse and why compulsive hot showering behavior relieves the symptoms is still under scientific investigation.