Opinion: Five years ago, many mocked a speech calling for liberalised drug laws. Today, such a position is becoming mainstream, writes former ACT leader Don Brash.

It is astonishing how rapidly attitudes towards marijuana are changing. Less than five years ago, most politicians thought I had lost my mind (indeed, perhaps had been smoking pot myself) when, in a speech as Leader of the ACT Party, I suggested that decriminalising, and even legalising, marijuana should be seriously considered.

The day after I gave that speech I was interviewed on Campbell Live. John Campbell invited viewers to text or email their opinions on the matter, and 72% of those who responded indicated they agreed with my view. Most politicians dismissed the “vote”, arguing rightly that it was in no sense a scientific poll.

Today, a UMR poll suggests that more than 70% of New Zealanders favour legalising medical marijuana, with people divided equally between those who favour legalising marijuana for personal use and those who remain opposed.

We’ve seen a similar shift in public opinion overseas. In 2011, the Global Commission on Drug Policy issued a report which began with the words “The global war on drugs has failed, with devastating consequences for individuals and societies around the world.” Instead of a policy of harsh law enforcement, the report advocated “decriminalising drug use by those who do no harm to others”.

And who were the people on this Commission? Twenty-two of the great and the good, including the former presidents of Brazil, Chile, Columbia, Mexico, Poland, Portugal and Switzerland, Kofi Annan, George Shultz (the former US Secretary of State), Paul Volcker (former chairman of the US Federal Reserve Board), and Richard Branson.

A month or two later, the Liberal Democrats in the UK – at the time in coalition with the Conservative Party – called for the decriminalisation of all drugs.

In October 2011, the California Medical Association called for the legalisation of marijuana (using cannabis for medical purposes had been legal in California since 1996). In the same month, Time magazine reported the results of a Gallup poll which showed that 50% of Americans favoured the legalisation of cannabis.

And so it’s gone on in the years since. In many US states, it is possible to acquire cannabis for medical purposes, and in several states marijuana is now fully legalised.

It appears that New Zealand may be catching up. Peter Dunne, in his capacity as Associate Health Minister, has recently approved the use of medical cannabis in a limited number of specific cases, and last week – following yet another international study which found that the punitive approach to drug offending hasn’t worked –“reiterated the Government’s commitment to review drug policy and make sure drug offending is primarily seen as a health matter”.

What do we know about marijuana?

We know first that, despite the current law making it a criminal offence to sell, possess or use marijuana, many hundreds of thousands of New Zealanders flout the law. The Law Commission undertook a major study on the issue in 2011 and noted that “nearly half this country’s adult population has used [cannabis] at some point in their lives and about one in seven, or the equivalent of 385,000 people, were classified as current users in 2006”. Indeed, although statistics are not entirely reliable, it appears that New Zealanders are amongst the heaviest users of marijuana in the world.

Second, we know from many studies that frequent use of marijuana by teenagers does quite serious damage to their developing brains. Perhaps the most comprehensive study was based on the internationally acclaimed study of 1037 babies born in Dunedin in 1972 and 1973, published in the Proceedings of the National Academy of Sciences in the US. This found that “adolescent-onset users experienced marked neuropsychological decline” amounting to some eight IQ points for persistent users. Other studies have found similarly adverse effects on teenagers. On the other hand, occasional use by adults appears to have minimally adverse effects, arguably less adverse effects than those caused by alcohol.

Third, we know that making the possession and use of marijuana a criminal offence does exactly what prohibition of alcohol did in the US – it substantially increases the power of the criminal gangs which supply the stuff. Because using it puts the user beyond the law, it probably also makes it easier for suppliers to entice users to try other more serious and more addictive drugs.

And of course because using it is a criminal offence, users risk incurring a criminal conviction for a crime which overwhelmingly does damage to the user himself, not to others, although getting the money to buy cannabis may well lead to much more serious crime.

So where does that leave me? It leaves me strongly in favour of legalisation but with one important caveat: every effort should be made to reduce – better still eliminate –the use of marijuana by teenagers, as is done with tobacco and alcohol. (And by the way – unlike many others, I have never used the stuff, and have no plans to do so.)