British doctors have connected marijuana use with rising rates of depression, psychosis and schizophrenia.

The Royal College of General Practitioners said that acceptance of the drug and greater availability of stronger forms of it were leading to rising rates of depression, psychosis and schizophrenia, The Telegraph of London reported Sunday.

“Health warnings are falling on deaf ears, drowned out by the cries of powerful liberal pro-legalization groups,” said Dr. Clare Gerada of the college’s drugs misuse unit.

“There is clear evidence that high levels of use, especially among teenagers who are physically and mentally still developing, carries with it the increased risk of psychosis and respiratory conditions such as asthma,” she said.

More worrying, Gerada said, was the increase in super-strong versions of the drug, known as skunk. “The truth is, genetically modified forms of the drug are the norm,” she said.

The British Medical Journal in its January 2005 issue revealed that smoking cannabis once or twice a week almost doubled the risk of developing psychotic symptoms later in life.

Robin Murray, a professor of psychiatry at King’s College London, has said that since the 1980s doctors have begun to see a link between psychotic symptoms and cannabis.