More than a third of people who present at Sydney emergency departments after smoking cannabis are violent and half have mental health problems such as severe anxiety and suicidal thoughts, shattering the image that dope smokers are relaxed and sleepy, researchers have found.
The data, collected by the National Cannabis Prevention and Information Centre, at the University of NSW, indicates that cannabis users can be as aggressive as crystal methamphetamine users, with almost one in four men and one in three women being violent toward hospital staff or injuring themselves after acting aggressively. Almost 12 per cent were considered a suicide risk.
"It flies in the face of what people typically think of cannabis - that it is a natural herb that makes people mellow," the centre's director, Professor Jan Copeland, said yesterday.
"The reality is that it can make people highly agitated and trigger acute episodes of anxiety."
She said the study, which covered two hospitals from 2004 to 2006, revealed that more than 9 per cent of cannabis users had depression or bipolar disorder, 5 per cent had schizophrenia and 4 per cent had paranoia and a history of self-harm.
"It's the first time we have ever gathered this data and it is highly surprising. It's apparent that we need a higher level of early intervention to pick up these problems before they get to the emergency department," Professor Copeland said.
The head of emergency at St Vincent's hospital, Gordian Fulde, said yesterday most people still believed marijuana was a soft drug, but "the old image of feeling sleepy and having the munchies after you've had a smoke is entirely inappropriate for modern-day marijuana".
"The grass we smoked in the '60s could have been lawn clippings compared to this completely different breed of nasty cat," he said.
"With hydroponic cannabis, the levels of THC [the active ingredient tetrahydrocannabinol] can be tenfold what they are in normal cannabis so we are seeing some very, very serious fallout."
Cannabis use was soaring among young professionals in the city and inner west, Dr Fulde said, but users rarely needed sedation.