It’s well known that alcohol
affects our ability to drive.
It’s a major road safety issue.
Drink driving is decreasing
but the incidents of drug taking
and driving is on the increase
and the effects
are little understood.
So the Transport Research Lab
is assessing the effect
of illegal drugs,
in this case cannabis, on driving.
We’re looking at cannabis
because we’ve just completed
a three-year study
of drugs in fatalities and we found
compared with a study
we did 10 years ago,
there’s been a massive increase
in illicit drug use
by a factor of about five or six
and the majority
of that illicit use is cannabis.
It’s a sophisticated protocol.
A double-blind, placebo controlled,
We first used a double-blind trial
because this means
that the participants
what dose they were receiving.
The double element means
that the person giving them the dose
and anyone else associated
closely with them in the trial
also didn’t know
what they were receiving.
Thereby they couldn’t contaminate
them in any sense
by influencing them in some way.
In one trial
they were given a placebo
which looks real but
has the active ingredient in cannabis
called THC removed.
The placebo controlled element
is very important
because people know
they’re part of an experiment.
They have been given something
but they don’t know what.
They’re going to react
in a particular way,
they maybe think
they’re getting something
and if they’re giving them nothing
and they still react
then this might look like an effect.
So you do want to compare them
against giving them nothing.
The cross-over design
gives another level of control.
The cross-over trial
in this context
was used because
we wanted to bring people in
to give them four different doses
People vary hugely between themselves
and vary less within themselves
the sort of activities involved,
driving type activities,
other laboratory experiments.
So we want a control
for that sort of variation,
we want to reduce the variation.
So we use them as their own controls.
To do that
we bring them in four times
and we call that a cross-over trial.
The participants were allocated
to one of three groups.
The groups being defined
depending upon the dose order.
In other words
participants in the first group
might have taken a placebo
on the first visit,
the low dose on the second visit
and a high dose on the third visit.
Participants in the second group
might have started with a low dose
and participants in the third group
with a high dose.
for this sort of trial
has got several tricky elements.
First and foremost we couldn’t
afford to use people who are naive
in terms of smoking cannabis.
Use of naive people
would be totally inappropriate.
They have to be users basically.
But of course smoking cannabis
or possession of cannabis
is an illegal act.
So we’re looking for people
who on a day-to-day basis,
at least a weekly basis in our terms,
were conducting an illegal act.
That’s slightly tricky
in terms of finding them.
You can’t just
put an advert in the paper.
So what do you do?
Virtually everybody you know
will know somebody
who probably uses cannabis.
So that’s the sort of route we took.
Do you think from
the Ethics Committee point of view
that would be completely acceptable?
They’ll want to see the way
that we propose to run the study.
Who’s going to be smoking what
And how we’re going to monitor it.
They’re going to want to see
that we’re taking some safeguards
the health of the volunteers,
that they won’t come to any harm.
But they shouldn’t do because
they’re already smoking the stuff.
also screened participants
to prove they were
regular cannabis users
and were not taking
other illegal drugs.
participants were monitored
over the course of the experiment.
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