Hi, great set of questions. I get asked these a lot so I realise most people aren't sure about these issues—so it's good to cover this ground.

Yes cannabis can be addictive. Many people who use cannabis report feelings of "addiction", which professionals call dependence, where they can't control their use, they need to smoke more cannabis to get the same effect, they spend a lot of time using cannabis, they will give up social or work activities to smoke, and they use cannabis even when it causes them problems. They also experience anxiety, poor appetite, restlessness or irritability, difficulty sleeping and dreams when they stop or cut down using cannabis.

Cannabis dependence is experienced by many users. The earlier a person begins using cannabis, the more likely they are to become dependent on it. About half of regular users would be considered dependent. Good news is that there are many effective treatments for cannabis dependence and the earlier a person seeks help the less likely they will experience problems.

Cannabis is not highly toxic (i.e. immediately dangerous), unlike drugs such as ecstasy or heroin, with no deaths from direct cannabis poisoning (overdose) recorded. However indirectly, cannabis use contributes to a high number of deaths on the road and maybe other accidental deaths.

In Victoria police have used roadside breath testing since 2004 to curb the number of drivers operating cars under the influence of cannabis. In the long term, cannabis use, like tobacco which it is often combined with, can lead to respiratory problems and possibly even cancers.

Other well recognised problems with cannabis are the negative effects it can have mental health. Many people experience feelings of panic, anxiety and paranoia. For people who have had psychosis, using cannabis can lead to further episodes. Other negatives come when combining cannabis with alcohol. This will intensify the feelings of each drug and can lead to unpleasant and unpredictable feelings such as "spinning out" or "greening out", which includes feeling dizzy, going pale and sweaty, feeling nauseous and sometimes vomiting.

Regular cannabis users also complain about feeling unmotivated—where they have no energy, withdraw from friends and can't be bothered doing anything socially or even getting things done at home. Some people who stop using can become abusive or aggressive due to feelings of extreme irritability. Cannabis may also have a negative effect on fertility, making it more difficult for women to become pregnant. It may also impact on newborns, leading to asthma, wheezing and chest infections if their mum smoked while pregnant. Babies can also be more unsettled and have a disrupted feeding cycle if the mum smokes cannabis while breastfeeding.

So overall, while cannabis won't kill you directly it is far from being the harmless herb that some people suggest it is.