The EconomistAugust 31st 2019 531T
he doctor was blunt with Hannah
Deacon, the mother of an epileptic boy.
He told her that she would “never” get a
prescription on the National Health Ser-
vice (nhs) for medicine based on tetra-
hydrocannabinol (thc), the psychoactive
ingredient in cannabis. The British govern-
ment, too, was unhelpful, maintaining in
February 2018 that cannabis had no medi-
cal value—a position that it had held for
over 50 years, even as the country grew and
exported cannabis for medicinal use. Yet
within months, it had made a u-turn, ac-
cepting thatCannabis sativahad medical
uses. Eight months after Ms Deacon made
her first public plea for it, her son, Alfie, got
thc-based medicine on the nhs.
Legislatures across the planet have been
having similar changes of heart. This may
presage broader legalisation. History sug-
gests that when medical cannabis is per-
mitted this is often the prelude to broader
recreational access.
People have exploited C. sativafor thou-
sands of years and its medicinal use can be
traced as far back at least as 400ad. But, like
other recreational drugs, it started to face
restrictions during the first half of the 20th
century. Fear-mongering was common. A
turning-point came in the 1900s when John
Warnock, a British expatriate doctor in
Egypt, suggested that cannabis was re-
sponsible for a large amount of the insanity
and crime in the country. When the League
of Nations met in 1924 to discuss narcotics
such as opium and heroin, his “evidence”
of the dangers of cannabis was influential.
But his methodology was dubious. Data
were gathered only from patients in the
Egyptian Department of Lunacy. He spoke
no Arabic, and an important way to deter-
mine if patients had been users was to note
their “excited” denials when asked if they
had tried the drug.Reefer madness
Then in the 1930s America was afflicted
with a moral panic, as cannabis was ac-
cused of inciting violence among Mexican
immigrants and of corrupting America’s
children. When the international system
of drug control, the Single Convention onNarcotic Drugs, was set up in 1961 at the Un-
ited Nations, the use of cannabis in tradi-
tional medicine was ignored. It was treated
as having limited or no therapeutic use,
and as being a dangerous drug, like heroin,
requiring the strictest controls.
Within the plant are chemicals called
cannabinoids, similar to molecules pro-
duced by the human body, known as endo-
cannabinoids. A wide network of receptors
in the human brain and body respond to
the plant and human versions of these
molecules. The body’s endocannabinoid
system is involved in regulating everything
from pain to mood, appetite, stress, sleep
and memory. So far, 144 different cannabi-
noids have been found in C. sativa—most
of them barely understood—and new prop-
erties are being discovered all the time.
The best known are thc, the ingredient
that gets you high, and cannabidiol (cbd),
which does not and which is increasingly
used as a food additive and supplement.
Drug treaties have severely impeded re-
search into cannabis. But over the years ev-
idence from clinical trials and elsewhere
has shown its efficacy in treating a range of
conditions, such as muscle pain in multi-
ple sclerosis, nausea induced by chemo-
therapy, treatment-resistant epilepsy and
chronic pain in adults.
Helpful both in alleviating pain and in
giving pleasure, pot has been wildly popu-
lar in the decades since the Single Conven-
tion and the drug-control treaties that fol-
lowed it. It is the world’s most widelyCannabis
Going to pot
A global revolution in attitudes towards cannabis is under way
International