There are already portable breathalyzers that let people put a number to their inebriation. However, what's a person to do if they want to receive a score on how high they are? Well, in the not-too-distant future, they could use the University of Chicago's "Am I Stoned" app.

First of all, the currently-in-development iPhone app is not intended to determine if the user is all right to drive, or perform other potentially-dangerous activities. Instead, it's designed more to help people understand just how susceptible they are to the effects of drugs such as marijuana, to keep them from overindulging.

To test an early version of it, a team led by Prof. Harriet de Wit started with a group of 24 healthy non-daily cannabis users, and gave each of them a capsule on three separate occasions. Some of those capsules contained either of two dosage levels of tetrahydrocannabinol (THC) – which is the ingredient in cannabis that makes people high – while others contained a placebo. Neither the test subjects nor the researchers administering the capsules knew which people were getting which.

After 90 minutes of allowing the THC to be absorbed, the test subjects got on a computer and took 15 to 20 minutes to perform a set of tasks known to detect impairment, plus they performed briefer versions of those tasks on the app. When their performance was assessed, it was found that three of the four computer tasks successfully detected which participants were high, but only one of the iPhone tasks did.

To that end, de Wit tells us that they are now refining the app tasks, to make them more sensitive to drug-induced impairment. App users will also initially have to perform the tasks while sober, to set a baseline.

"One of our long-term goals is for the app to improve the safety of cannabis use by making individual users more aware of their impairment," she says. "By gathering data from users in the field, the app will also contribute to the overall scientific knowledge in terms of how cannabis affects users."

The team's findings are being presented this week, at the 2018 Experimental Biology meeting in San Diego.

And if you think that a straight-up marijuana breathalyzer is the way to go, well, scientists at the National Institute of Standards and Technology are working on it.