BBC News 18 February 2015
Cannabis is bad for you, cannabis is good for you – confused?
That’s not surprising. Complicated and controversial, cannabis is revealed by recent science to have a dual personality, with a dark side and a more positive one. Radio 4’s PM programme is this week running a whole series on cannabis, and the debate surrounding it.
Key to understanding this strange plant are two of the ingredients that make it up, known by their initials as THC and CBD.
I asked Professor Val Curran of University College London to describe how they work and she came up a memorable answer:
“In a way, THC and CBD are a bit like yin and yang. The THC makes you stoned, but it can also make you anxious. It can also make you feel a bit psychotic, and it will seriously impair your memory.
“The other side of the yin/yang is CBD, which has almost the opposite effects. CBD calms you down, it has anti-psychotic properties and it also offsets the effects on memory, so that on CBD-containing cannabis you’re less likely to forget what’s going on.”
So the first step to understanding cannabis is to realise how it can vary, how different types contain very different quantities of these polar opposites, with dramatically different outcomes.
The weed so familiar to many of my generation was characterised by a relatively balanced amount of THC and CBD.
Today, the vast majority of cannabis on sale on the streets is unrecognisably stronger.
Known as skunk, it contains a far higher proportion of THC – as much as 15% – which produces a much more powerful high, making it more appealing for users.
But, at the same time, because it hardly contains any of the CBD that might lessen its effects, the risks are correspondingly greater.
Prof Curran is among those worried about its potency.
“What concerns me is that on this high-THC skunk, people will experience more memory problems, which could affect how well they do at school. And in terms of addiction, 10% of people who use it will become addicted to the drug.”
According to a study by two researchers at UCL, Dr Tom Freeman and Dr Adam Winstock, the strongest cannabis increases the risk of addiction, along with memory loss and paranoia.