NEW YORK (Reuters Health) - Various reports indicate that young people who use cannabis tend to experience psychological and social problems. However, there is no evidence that marijuana use is directly linked with such problems, according to the results of a study published in The Lancet. "Currently, there is no strong evidence that use of cannabis of itself causes psychological or social problems," such as mental illness or school failure, lead study author Dr. John Macleod of the University of Birmingham in the UK told Reuters Health. "There is a great deal of evidence that cannabis use is associated with...