Your phone can tell when you’re high: Data from accelerometer and GPS sensors can be used to predict with 90% accuracy if someone is stoned, study finds
Sensors on a person’s smartphone can be used to determine if they’re high with uncanny precision, according to a new study out of Rutgers University
Researchers at the school’s Institute for Health, Health Care Policy and Aging Research found that an algorithm that combined sensors tracking movements and GPS location with data on the time of day and day of the week had a 90 percent accuracy rate in determining if someone was stoned.
The algorithm could help law enforcement and health professionals more accurately predict if an individual is currently experiencing ‘cannabis intoxication,’ according to a release.
‘We might be able to detect when a person might be experiencing cannabis intoxication and deliver a brief intervention when and where it might have the most impact to reduce cannabis-related harm,’ said co-author Tammy Chung, director of the Institute’s Center for Population Behavioral Health in the statement.
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Researchers have been able to create an algorithm that predicts whether a regular pot smoker is high with 90 percent accuracy. The system combines GPS and movement data from their smartphone with info on the time of day and day of the week
The study, published in the journal Drug and Alcohol Dependence, evaluated the feasibility of using smartphone sensor data to identify episodes of ‘cannabis intoxication’ — being noticeably high— in a non-lab environment.
The researchers collected daily data from volunteers in Pittsburgh ages 18 to 25 who said they smoked marijuana at least twice per week.
Using self-initiated reports and phone surveys over a 30-day period, the researchers developed an algorithm that could accurately predict if a participant was high with 60 percent accuracy just based on the time of day and day of week.
Adding in continuous data gleaned from smartphone sensors boosted that rate to 90 percent.
Just based on the time of day and day of week, the algorithm had a 60 percent accuracy rate
The most important phone features in detecting cannabis intoxication were travel patterns from GPS when a subject said they felt high and movement data from the device’s accelerometer.
Typically, an accelerometer measures different motions — like tilting or swinging — and changes the orientation of your phone’s display from portrait to landscape accordingly.
It can also detect a sudden change in acceleration, like if you drop your phone, and shut off the hard drive to prevent data damage, according to software developer Credencys.
Getting high has been linked to slower response times, which can impair driving and other focus-intensive activities.
Existing marijuana detection measures — like blood and urine tests — present logistical issues and would be too time-consuming to use as an intervention.
In addition, such tests can return positive results for up to three days after a subject has last used marijuana and would no longer be considered high.
As more states legalize marijuana, a smartphone app could be used to determine acute cannabis intoxication, rather than just general usage.
The authors of the study, who include faculty from Stevens Institute of Technology, Stanford University, Carnegie Mellon University, University of Tokyo and the University of Washington say future research should investigate how algorithms like theirs would rate in classifying people who use weed less frequently.
Most current marijuana tests can return positive results for up to three days after a subject has last used pot. The algorithm could help ‘detect when a person might be experiencing cannabis intoxication and deliver a brief intervention when and where it might have the most impact,’ researchers say
Currently, 18 states and the District of Columbia have legalized recreational marijuana and another nine approve its use medically.
An article published Monday in the Journal of the American Medical Association found there was no increase in cannabis use among the general population or previous users after their states legalized marijuana.
In September, Senators Cory Booker, Ron Wyden and Chuck Schumer introduced the Cannabis Administration and Opportunity Act, which would decriminalize marijuana on the federal level.
WHY IS IT DIFFICULT TO DEVELOP SOBRIETY TESTS FOR MARIJUANA?
Determining when someone is too high to drive is a problem that has evaded the chemists, psychiatrists, law enforcement agents and public policy makers.
Scientists explained to Daily Mail Online why the most scientific tests may not be the best way to determine how high is too high and the unique chemistry that makes marijuana a drug-screening enigma.
Some are unique to the drug, but one is true of just about any substance: tolerance.
Depending on how often and in what doses someone uses any substance, the amount it takes to for the drink or drug to have an effect varies drastically.
So, people with medical marijuana prescriptions, for example, who might smoke weed every day, seem totally unaffected and breezily pass a field sobriety test – which involves tests for coordination and balance, like walking the line, as well as some for memory and attention – even though they’ve recently ingested lots of the drug.
Beyond that, marijuana moves through the body in a very different way from alcohol.
Marijuana – more specifically, its psychoactive component – leaves the blood very quickly, but it lingers in the fat and brain, meaning its cognitive effects do, too.
According to Dr Richard Clark, director of the division of medical toxicology at the University of California, San Diego, marijuana may even move from these tissues back into the blood days later in ‘chronic’ smokers.
And just to add an extra level of difficulty, the THC in increasingly popular edibles gets converted quickly to anther compound in the stomach, so a THC test might not even detect it, even when a high was in full effect.
Blood and urine tests are available, but sometimes a long time passes between when someone is pulled over and when the test can be administered.
There are two recently developed breathalyzers for THC – one from Hound Labs and another from Cannabix – and several other tests in development, but these face the same challenges of disparity between blood level and actual high.
‘Field sobriety testing introduces subjectivity into something you’d really like to be subjective,’ says Dr Hall.
For now, however, no method is perfect.
‘So what does it all mean,’ Hall said, ‘except it’s better to drive completely sober.’
-Natalie Rahhal, Deputy Health Editor for Dailymail.com