The Swiss government is questioning the results of a study showing a link between marijuana use and schizophrenia.
The Zurich University study showed a higher incidence of schizophrenia in the 1990s in the age groups most likely to use cannabis, Swissinfo said Wednesday.
"We know from other experimental studies that cannabis can cause psychosis, but we have now established a clear link to schizophrenia for the first time," study co-author Wulf Rossler said.
Swissinfo said the Federal Health Office is questioning the report, saying the patients' drug histories and other medical details remained unknown.
"It does not uncover the medical history of the patients, for instance the consumption of psychotic substances or other factors that could lead to psychotic illnesses," the health office in a statement.
Copyright 2007 by United Press International
Explore further: Clearing up confusion between correlation and causation