Your smartphone can tell if you have consumed marijuana

Cannabis intoxication has been associated with slow response time.

A smartphone sensor, much like what is used in GPS systems, might be a way to determine whether or not someone is intoxicated after consuming marijuana, a new study suggests.

The study, which evaluated the feasibility of using smartphone sensor data to identify episodes of cannabis intoxication in the natural environment, a combination of time features (tracking the time of day and day of the week) and smartphone sensor data had a 90 per cent rate of accuracy.

"Using the sensors in a person`s phone, 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 researcher Tammy Chung from Rutgers University.

For the study, published in the journal Drug and Alcohol Dependence, the researchers analysed daily data collected from young adults who reported cannabis use at least twice per week. They examined phone surveys, self-initiated reports of cannabis use, and continuous phone sensor data to determine the importance of time of day and day of the week in detecting use and identified which phone sensors are most useful in detecting self-reported cannabis intoxication.

They found that time of day and day of the week had 60 per cent accuracy in detecting self-reporting of cannabis intoxication and the combination of time features and smartphone sensor data had 90 per cent accuracy in detecting cannabis intoxication.

Cannabis intoxication has been associated with slowed response time, affecting performance at work or school or impairing driving behaviour leading to injuries or fatalities.

Existing detection measures, such as blood, urine or saliva tests, have limitations as indicators of cannabis intoxication and cannabis-related impairment in daily life.