LEIGH SALES, PRESENTER: A powerful grass-roots campaign around the country has prompted federal and state politicians to embrace a push to legalise the use of marijuana as medicine.

New South Wales and Victoria are moving toward clinical trials, Tasmania is holding an inquiry and the Greens are pushing a private members bill to allow cannabis to be used to treat a range of ailments. Under the proposals, the patients treated with the drug would include children.

But some doctors are sounding a warning. They say emotional parents desperate for a cure for sick youngsters have hijacked the debate.

They also warn the scientific jury is still out on the medical effects and that cannabis can cause serious mental health problems - and even prompt suicide.

While marijuana producers and doctors who advocate its use wait for legalisation, some are openly flouting the law, as Conor Duffy reports.

CONOR DUFFY, REPORTER: In this suburban garage a crop's about to be harvested. It's not your average herb garden: it's hydroponic marijuana.

Former GP Andrew Katelaris is one of the key players at the centre of this controversial drug push.

ANDREW KATELARIS, DR, FORMER GP: Well, these tents are a very convenient way for people to produce their own cannabis. The setup costs would be about $1,000.

CONOR DUFFY: This is how medical marijuana works in Australia at the moment: Andrew Katelaris, a deregistered doctor spurned by the medical fraternity, believes these illegal mobile stash houses provide a valuable service.

Do you worry at all about what the wider medical establishment will think?

ANDREW KATELARIS: Well, they should worry more about what I think of them. I mean, it's been a very sad journey having very valid and very exciting scientific work being either ignored or denigrated or obfuscated by the medical profession.

The process is very, very simple...

CONOR DUFFY: Back at home in his kitchen, he mixes a rare strain of cannabis imported from Spain that's rich in the medically useful cannabinoid CBD but low in THC, the part of the plant that gets you stoned.

ANDREW KATELARIS: What we can do: we can make specific oils depending on their intended end use, right? For instance, I might combine this as a predominantly CBD cannabis with more THC cannabis depending on what we're treating. If we're treating, say, a child with seizures and spasticity, they generally do fairly well with some THC included.

CONOR DUFFY: He follows a special recipe, mixing pot with oil and heating it to about 50 degrees.

In 12 hours we'll filter and decant it into a bottle and it will be sealed and labelled and shipped for patient use.

This batch of hash oil will end up with 12 children around Australia with rare forms of epilepsy who take it several times a day. He claims it's succeeded where all other drugs have failed.

Literally, kids are going from wheelchairs to pushbikes. They're going from reading ages of three to eight in a couple of months of cannabis therapy.

Ten-year-old Hunter Elwell from the central coast of NSW is one of the children receiving medical marijuana. His mother Lorraine is an unlikely law-breaker. She gets jars from Dr Katelaris, places the oil into a syringe and feeds it into his stomach through a tube - the same way he gets his food.

LORRAINE ELWELL, MOTHER: OK? There you go. Good boy.

CONOR DUFFY: Hunter is 10 years old and he has Dravet syndrome, which is classified as a catastrophic seizure disorder and it's resistant to most, if not all anti-seizure medications.

Hold on, mate.

CONOR DUFFY: Hunter's seizures were so frequent and painful, he was regularly flown to hospital and given adult painkillers like morphine and fentanyl. Medical marijuana has transformed their lives.

LORRAINE ELWELL: Great. He hasn't had... in the 18 months he's been on it, he hasn't had one paramedic call for seizures at all. He hasn't had a stay for seizures in hospital and he probably has about four or five seizures a month now.

CONOR DUFFY: And what was it before?

LORRAINE ELWELL: Up to 20 to 30 a day. Yep. And that was on a good day. Yes. There were times when he was in hospital for three months because he was having a seizure every 30 seconds.

ANDREW KATELARIS: Here's another form of delivery using an aerosol. It's particularly useful as a rescue remedy.

CONOR DUFFY: Andrew Katelaris' kitchen is full of exotic cannabis sprays and oils. He's working on a mouth spray to rescue epileptic children from fits.

But he's a controversial figure, banned from practicing medicine because of a long history of taking and supplying cannabis and other scheduled drugs to patients and with a previous conviction for growing a medical marijuana crop.

It can also be reconstituted. For instance, if I have...

CONOR DUFFY: There are no formal scientific controls and many doctors would be concerned the parents he supplies are left to regulate their own doses.

They may well be concerned and I'm sure there's a fair bit of tut-tutting but the results speak for themselves. I'm providing a safe and effective herbal medicine which in this backwater country has been made illegal - and currently remains illegal - whereas around the world medical cannabis is now freely available.

EMMA ALBERICI, PRESENTER (Lateline, ABC TV, Sep. 16): In NSW the Baird Government has announced a clinical trial of medicinal cannabis.

CONOR DUFFY: Two state governments are moving toward further trials of medical marijuana and even the Prime Minister has endorsed it as momentum builds.

NICHOLAS TALLEY, PROF., ROYAL AUSTRALASIAN COLLEGE OF PHYSICIANS: I think we need to be very, very careful.

CONOR DUFFY: Some doctors, like Professor Nicholas Talley, support trials but fear children and adults using medical marijuana now are putting themselves at risk.

NICHOLAS TALLEY: So for example, people who drive and are taking marijuana: well, they're putting themselves and others at risk. There's an increased risk, based on studies, of suicide. There's an increased risk of certain cancers with chronic marijuana use. This is not a totally safe product, like some people - in fact, perhaps many people - believe.

(Footage of medical marijuana dispensaries, Venice Beach, Los Angeles)

SPRUIKER: Medical marijuana evaluations. The doctor is in.

(Footage ends)

CONOR DUFFY: Overseas there has been more than 90 studies of medical marijuana. Professor Talley says, at best, they provide inconclusive evidence cannabis can treat a small number of conditions.

NICHOLAS TALLEY: Areas where there might be some benefits: nausea and vomiting, particularly from chemotherapy - although there are better options, according to the experts in most cases and marijuana can cause you to vomit, so it's not as simple or as straightforward as one might think; some pain conditions not responsive to other things - although, again, the evidence is not very conclusive; spasticity problems; perhaps rare forms of epilepsy.

CONOR DUFFY: Doctors here believe their overseas counterparts have struggled to find the right dose level and a safe way to give it to patients.

NICHOLAS TALLEY: The problems have been that practitioners don't quite know how to dose, how to prescribe, how to ensure people will actually get effective levels of drug, what the effective levels are, who to prescribe it for, what indications.

They're pretty serious issues.

CONOR DUFFY: Professor Iain McGregor is one of Australia's most experienced drug researchers. He also wants more trials but believes the illnesses medical marijuana is treating are so serious that immediate use is an acceptable risk.

IAIN McGREGOR, PROF., PSYCHOPHARMACOLOGY DEPT., SYDNEY UNI: I think where you've got, you know, people who are suffering abominable levels of pain - for example in end-stage cancer - why would you deny them any sort of medicines that is potentially useful? Similarly, in childhood epilepsy, if you have kids that are having 50 seizures a day, you can't imagine what that's like for the child and for their parents.

CONOR DUFFY: Professor McGregor led a groundbreaking study that laid out some of the risks of sourcing your own weed for medical use in Australia.

IAIN McGREGOR: We did the first ever analysis of street cannabis in Australia and what we found was that the street cannabis was very high in THC - so very potent in terms of its ability to intoxicate - but it was actually very low in the good cannabinoids. And this is quite distressing from the point of view of mental health in particular.

CONOR DUFFY: The holy grail is coming up with strains of marijuana that won't get patients high but will treat a range of conditions from multiple sclerosis to cancer sickness and spasticity. That will mean expensive trials.

IAIN McGREGOR: I would make a special plea that we start looking at cannabis and particularly these different cannabinoids as potential wonder medicines and start to run proper clinical trials, looking at their efficacy in a whole range of different conditions.

ANDREW KATELARIS: Medical cannabis is a life saver; it's a game-changing medication for these people.

LEIGH SALES: And you can join Andrew Katelaris from that story in a discussion about medical marijuana on our Facebook page.