Cannabis will be classified as a class C drug from Thursday
Thousands of posters are being sent out to schools and colleges across
Northern Ireland warning that cannabis is still illegal.
It coincides with new legislation coming into existence on Thursday, under which cannabis will be considered a class C drug instead of class B.
The government has begun a major campaign to alert users
to the law changes, with more than 100,000 leaflets going to schools, employers and voluntary and community organisations.
Another 4,000 posters are being put up in pubs and clubs using phrases such as "collared", "nicked" and "nabbed" to try to drive home the message that users are breaking the law.
Northern Ireland's Criminal Justice Minister John Spellar said arrests for possession could still be made.
"Reclassification does not mean that cannabis is now a legal
drug, or that it is not harmful to health," he said.
"It is against the law to have, give away, or deal in cannabis in any form,
John Spellar: Warned of dangers of cannabis
"While this campaign does not specifically spell out the dangers to health,
these haven't changed as a result of reclassification.
"Smoking cannabis could harm your health yesterday and it can equally harm
your health today."
The decision to reclassify the drug was taken by Home Secretary David Blunkett following advice from the Advisory Council on the Misuse of Drugs.
Even though the body concluded the drug was not harmless and posed risks to health and society, it said it was less harmful than other class B substances.
As part of the reclassification, the maximum penalty for trafficking in class C drugs is being increased from five to 14 years.
But Professor Robin Murray, a mental health expert, said studies had demonstrated the danger of increased cannabis use.
Speaking after attending a mental health conference in Belfast, he said:"Schizophrenia might go up by 25%. That would be my expectation."
Professor Murray said tests carried out on 1,000 people monitored over a period of 10 years found those taking the drug at the age of 15 were nearly five times as likely to develop schizophrenia by the age of 26.