Heavy cannabis use is consistently associated with poorer attention and memory, and increased rates of metal health problems. Pe3k/F/ShutterstockGovernments and communities worldwide are softening their views on cannabis use. Trials of medicinal cannabis have been approved in Victoria, Queensland and New South Wales. And the Australian parliament is currently debating legislation to introduce a government regulator of medicinal cannabis. This follows decriminalisation of cannabis in Portugal and its legalisation in Uruguay and several US states. Cannabis is still the product of choice for many illicit drug users in Australia. Five times as many people use cannabis rather than cocaine or methamphetamines. But debate remains about the long-term effect the drug has on the brain, cognition and mental health. Most cannabis users start as