Will cannabis give you hangover or ‘stone-over’? An effect where you still feel impaired or dozy after a late night consuming cannabis.
If so, it has real implications for guidance on anyone consuming cannabis, who then has to work the next day using machinery or even driving.
For example, current drug driving laws use tests that look for THC in your saliva, hair, or blood. You can test positive, even if you consumed many days before the test.
So this begs the question – is it safe to work or drive the day after consuming cannabis? Does cannabis give you a hangover?
Evidence of effect of cannabis on performance
A study by Dahlgren in 2020 indicated that chronic long term use of errr..chronic, was associated with impaired driving.
Notably, participants were not actually intoxicated or obviously impaired at the time of undergoing a driving simulation test.
They had not actively consumed cannabis at least twelve hours before taking the test, but the study reported that their driving abilities were still affected.
This has major implications for anyone using cannabis long term. Even though you might not feel ‘impaired’, it could you make more likely to have a road traffic accident.
The study’s conclusion was that as cannabis use increases globally in line with increasing legalisation, policy markers need to be aware of the long term use of cannabis on driving impairment. But hang on!
The study also looked at the age at which people had started using cannabis. It was only those people who had started using the herb below the age of 16 who suffered impairment in the driving sim.
The role of personality in cannabis hangover
In the study, participants also completed a survey on their impulsivity. For example, do they speak before they think, do they pay attention, or are they likely to be planful before taking action?
Once natural impulsivity was discounted, there was very little evidence to show impact of long term cannabis on driving ability.
Surely, this means that it’s actually the higher impulsivity which makes you a worse driver? Somebody who doesn’t naturally ‘pay attention’ might be considered more dangerous when behind the wheel, than someone who is not under the influence of drugs.
Emerging evidence of the cannabis hangover
A very recent study in 2023 asserts that next day impairment of performance has been claimed by ‘low quality’ studies.
Low quality studies are generally where the scientific methods of testing theories are not robust enough, or conclusions made are not valid, given the evidence presented from the study.
209 out of the 345 tests conducted across 16 published studies showed no “next day” effects of THC. Nine of these 16 studies used randomized, double-blind, placebo-controlled methods, which is a much more robust way of testing for theories.
Indeed 12 out of 345 tests concluded that the “next day” effects of THC are real and do impair you, but none of them used randomized, double-blind, placebo-controlled designs and all were published more than 18 years ago.
Using cannabis and driving is illegal in the UK. If you are intoxicated when driving, then you are taking a huge risk, and could kill someone. You face being arrested and losing your licence, or even a criminal record.
Of course, many people will drive stoned and claim that they are still safe, and that’s its much less of a risk than drinking alcohol and driving. Obviously, we do NOT recommend that.
But the testing regime for drug driving is a blunt tool. It presumes that anyone who has consumed cannabis within the last week or so, is unable to drive.
This is largely in part due to outdated laws, poor research base, and a continuing narrow view on cannabis in many countries, particularly the UK.
At the same time, this is completely at odds with the guidance for medical cannabis users in the UK. Current government guidance is that if you feel affected by the cannabis, then you shouldn’t drive.
Many medical cannabis prescription labels read ‘Don’t drive unless you know how this medication will affect you” which to us says that you can drive if you feel that you’re ok, and have a legal prescription for cannabis.
Ultimately, the picture is complex, but the evidence is starting to contradict that idea that getting stoned, impairs you the next day, or indeed gives you a ‘hangover’.