Even if you don't smoke cannabis, you have probably heard the term “contact high” and wondered if it's something that really exists. Maybe you've even questioned if you've gotten one yourself after spending a little too much time at your marijuana-loving friend's apartment or getting stuck in a “hot box” situation.
To clear up any confusion, a “contact high” refers to the psychological phenomenon a sober person can experience simply by being near people smoking cannabis, and to this day cannabis users and non-users alike debate as to whether you can really get a one. Until recently, scientific research on whether or not contact highs really exist have been scarce, but as the scope of research into marijuana widens, science has been reexamining the concept of a contact high. So far, studies have shown that under certain conditions, the smoking of cannabis can produce the same psychological effects (on a milder scale) in non-smokers who are close by.
For example, a 2015 study led by researchers from Johns Hopkins University School of Medicine tested the effects of lingering smoke from cannabis on non-smoking subjects. The experiment put a group of six people smoking cannabis and another group of six non-smokers together in a sealed Plexiglas room with manually controlled ventilation mechanisms for 1-hour intervals. Some trials exposed the subjects to unventilated conditions, while others allowed for a ventilation rate of 11 air exchanges per hour.
Researchers found that “under extreme, unventilated conditions, secondhand cannabis smoke exposure can produce detectable levels of THC in blood and urine, minor physiological and subjective drug effects, and minor impairment on a task requiring psychomotor ability and working memory.” The unventilated trials resulted in the six non-smoking subjects experiencing inhibited cognitive skills, increased heart rates, and sedative effects. The non-smoking participants also had detectable levels of cannabinoids in their blood and urine after the unventilated sessions.
To end, it seems that “contact highs” do exist to some degree and an environment's ability to circulate fresh air plays an important role in whether someone will experience a one from others smoking cannabis around them.