For someone with schizophrenia who has used cannabis, to say it doesn't cause schizophrenia, I am either delusional or well informed.

I am a mental health specialist journalist, and have spoken to various scientists at the leading edge of research, in my personal quest to find answers about my own illness. I also understand the logical pathways involved in the descent into delusion or conspiracy theory. I get delusions, and like the conspiracy theories I see in my journalism, enjoy picking them apart.

The fact is, no direct links can be shown between cannabis and schizophrenia at present. In an article for another title I spoke to a government scientist who told me that the links have all been researched, and no researchers at all globally are looking at the links any more - because it is widely regarded as being impossible to find.

My first psychiatrist explained to my father that 1 in one hundred people among the world population will develop schizophrenia. You could be the son of Rupert Murdoch and develop schizophrenia, or you could be a nomad in Mongolia and have the same chances.

As someone with a psychotic illness I have a genuine fear of the readership of the UK tabloid newspaper the Daily Mail. To those that believe everything they read in said paper I am not a married journalist and social justice campaigner, but someone with severe risk of murdering someone in the street who should be locked up indefinitely merely for having mental illness. I often end up in combat with them, generally arguing until they get aggressive and start raving, making me scared they may have a knife on them.

I take everything I read in that paper with a pinch of salt. In July 2007 it came up with the unshakeable truth that you have a much higher chance of developing schizophrenia if you smoke a joint. 'The researchers, from four British universities, analysed the results of 35 studies into cannabis use from around the world. This suggested that trying cannabis only once was enough to raise the risk of schizophrenia by 41 per cent.'

Speak to one of those researchers about what they do as scientists, and they will tell you they cannot 'prove' anything. They can show something though. I could do a study of the psychology of Daily Mail readers and show how dangerous to society said paper is, and argue that those who read it should be locked up indefinitely merely for reading the paper. I can't prove you are dangerous merely because you read it - I can show, though...

A blog on the Cannabis Law Reform (CLEAR) website counters the argument made by the Daily Mail. Referring to 2009 study by Dr Stanley Zammit, one of the world's leading schizophrenia researchers, it shows that 'if cannabis did cause schizophrenia then to prevent just one case in adults over 20 or so, we would have to prevent around 3,000 heavy cannabis users, or 150,000 light users.' It should be stated that Zammit was one of the researchers in the paper referred to in the Daily Mail article - research often counters itself, and with Zammit showing one argument and then another, you will see that proof does not come easily.

Speaking to Zammit for my 2007 book (Giving Voice to the Inner Scream, now out of print) he told me that THC, one of the psychoactive ingredients of cannabis, is used to induce psychotic symptoms in medical research. Less known in common understanding of cannabis is another ingredient called Cannabidol (CBD) which is shown to cause antipsychotic effects - a counterbalance to THC's psychotic effects. The CLEAR blog quotes another study which suggests that 'determining how the constituents of cannabis act on the brain is fundamental to understanding the role of cannabis use in the aetiology of psychiatric disorders'.

In the case of THC induced psychosis the condition is known as a temporary disorder termed 'toxic psychosis'. Toxic psychosis leaves the brain soon after the chemical causing it has been digested - different to what may be termed 'organic psychosis', one of the symptoms that dogs me permanently.

Psychosis is only one symptom of schizophrenia. The Royal College of Psychiatrists has an easy to understand explanation of the various symptoms someone with schizophrenia can have here. Broadly you must have 'positive symptoms' AND negative symptoms. If you believe that Rupert Murdoch is head of the Bilderbergers and rules the world, that is a positive symptom - but you are only a conspiracy theorist if you believe that and do not have negative symptoms. Negative symptoms include lack of insight - not being able to understand that you are mentally unwell - and thought interruption - the inability to keep to a thread of thought, such as reading this article to the end.

In a 2010 article for the social workers' journal Community Care I concluded that my schizophrenia is multifactorial in causation. I suggested that 'It seems that a combination in my case of genetics, prolonged stress and cannabis may have reached the critical mass responsible for the disorder developing.' If I was not predisposed to the illness, cannabis probably would not have contributed to organic psychosis. I may have joined my fellow undergraduate university smokers and led a successful life beginning in my 20's, as opposed to my 30's as would happen in the end.

Does this mean I can enjoy a spliff personally? No. Nor can I enjoy a drink of beer down the pub because alcohol was also a contributing factor to my psychosis. People who are susceptible to psychosis should not smoke cannabis. Cannabis campaigners say just this: 'a bad reaction to cannabis might be an early warning that a person is likely to develop schizophrenia'. In the same way, choking and spluttering my way through my first cigarettes as a youngster, I should have taken the message instead of becoming hooked to a drug that has a verifiably high chance of killing me!

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