Cannabis continues to be the world’s favourite illicit drug with
around 147m people
using it annually. However, there are fears that the drug is
becoming
increasingly potent and that it could pose a public health risk.
But how reliable is the evidence? And is it really getting stronger?
The debate about cannabis potency and harm is long running. In
the UK, where there are 2m annual
users, it predates the
2004
downgrading of cannabis classification from class B to class C.
But this episode demonstrated some of the issues with estimating the
harms of the drug. Research conducted at the time highlighted how
the relative harms of cannabis compared with other class B
substances was one of the factors behind the decision to reclassify.
However, critics accused the government of ignoring emerging
evidence that cannabis was becoming more potent and that it
represented a serious public health problem.
Those more sympathetic to the change in classification questioned
whether this interpretation of cannabis potency was accurate,
highlighting how an alternative conclusion had been drawn from
published research which suggested only modest changes in cannabis
potency over the
20 to 30 years prior to 2004.
Others, meanwhile, questioned the relevance of potency evidence,
pointing to a shortage of studies looking at the consumption of
cannabis in a natural setting and how users may well be smoking
higher strength strains, but that they could be
“titrating” their doses as a consequence, for example, by taking
smaller puffs.
The debate over potency is not helped by politicians referring to
the “lethal
quality” of today’s cannabis and although the evidence is
inconclusive, there is widespread acceptance that strains of
cannabis are stronger than in previous decades.
To date, most assessments of cannabis potency have focused on
increasing levels of
tetrahydrocannabinol (THC). But this doesn’t provide the full
story. Cannabis contains hundreds of compounds, some of which
interact with each other. For example, THC helps the user get high,
but another compound, cannabidiol (CBD), can counter this by
reducing unpleasant feelings such as anxiety. So it is the balance
between THC and CBD over time that is important.
It would seem that many cannabis producers have competed to
incrementally increase THC levels while selectively breeding out the
more
protective cannabinoids. Seizures from the US Drug Enforcement
Administration show how this ratio has changed in America over the
last 20 years.
This changing ratio was helped in the UK by the introduction of
hydroponic techniques in the 1980s for cultivating cannabis.
Proxy problems
Proxy measures of cannabis potency such as those based on home
seizures of cannabis are
widely used and quoted. But we don’t know if the cannabis seized
is a representative sample of the cannabis in circulation. Steve
Rolles, senior policy analyst for Transform Drug Policy Foundation,
describes it as “a massive data hole”.
Also, the quality and sophistication of the cannabis testing
procedures, such as chromatography, used to analyse seizures has
improved over recent decades. But this means seminal and widely
quoted research is outdated and less relevant.
Another factor to consider is how much cannabis is consumed in
the average joint. A recent analysis of over 10,000 cannabis
transactions carried out in the US between 2000 and 2010, estimated
that the
average joint contains 0.3g. This is significantly lower than
the previous estimates of 0.75 to 1g.
Other factors that influence the strength of the hit are how
deeply you inhale and how long you hold the smoke in your lungs.
The method used to ingest the drug also influences a user’s
experience, such as eating, vaping or smoking. Dose can be increased
by using a bong whereby a greater quantity of the drug is inhaled in
one go compared to a single hit on a joint. Higher potency
concentrates known as “dabs” have the potential to
alter the level of intoxication .
Without any quality assurance system such as the one recently
introduced
at a festival, it is likely that younger users – who haven’t
been using cannabis for long – are the most vulnerable to variations
in cannabis potency.
There are public health implications. Cannabis users have to rely
on their own knowledge when deciding on the dosage to achieve the
desired high. A regulated market such as the one in
Colorado could mean users are able to make better decisions and,
in turn, reduce the rate of people needing treatment services where
cannabis is the primary problem .
The government should regulate cannabis products to make them
safer, enabling consumers to make more informed choices. It should
create opportunities for targeted education and harm reduction, and
employ other evidence-based health interventions.
The science underpinning the cannabis potency story is
problematic. With so many people using cannabis, it can’t be
acceptable to continue with a system where basic information about
this product’s strength and purity are obscure. It is time for a
national survey of cannabis that not only provides information about
the strength of cannabis but how exactly it is consumed, too.