Study: Weed Makes You Paranoid. No, Really?

Tell us something we don’t know. A new study out of Britain confirms a painfully obvious fact about marijuana use: It tends to make users paranoid.

Researchers Daniel and Jason Freeman, who wrote about their results in the Guardian, studied 121 people who had used weed at least once, had never been diagnosed with a mental illness, and reported paranoid thoughts within the past month.

All the participants got an injection, with two-thirds receiving as much THC as a “strong joint” and the other third receiving a placebo. Scientists closely monitored paranoia levels in the subjects.

Half of the participants who received THC reported paranoid thoughts, compared to 30 percent of the placebo group. That’s a statistically significant difference.

“That is, one in five had an increase in paranoia that was directly attributable to the THC,” the researchers wrote. The study demonstrates that “paranoia isn’t tenuously linked to THC: For a significant number of people, it’s a direct result.”

Paranoia is an unfounded or excessive belief that someone is out to hurt you. Whether it’s a knock on the door from the cops or an unexpected phone call from grandma at 2 a.m., the fear is real but unreasonable. That doesn’t necessarily mean it’s wrong, only that your anxiety is out of whack with reality.

Cannabis users are more susceptible to these thoughts than other people, the study found.

“[T]he belief that people are deliberately trying to harm you is three times as common among cannabis users as it is among non-users,” the researchers wrote. “The belief that people are trying to cause you serious injury or harm is five times as common among cannabis users.”

THC also appeared to cause other negative mental symptoms, including negative thoughts, anxiety, and depressed mood. It’s also responsible for “anomalous experiences” such as an altered sense of time and space.

The paranoia, the researchers wrote, could result from the confusion caused by these symptoms, combined with a vulnerable mood state.

weed make users paranoidIt’s not news to anyone who’s smoked more than a few tokes of weed that paranoia comes with the package. So do memory lapses and distortions in perception. These inconveniences are practically a way of life for many chronic smokers.

And they aren’t likely to go anywhere anytime soon. Paranoia can be especially annoying to first-time users, who aren’t prepared for the sensation, though it always subsides.

And that’s the good news out of this study. As THC leaves the body, paranoia vanishes.

Maybe someday science will discover a cure for weed-induced paranoia. In the meantime, it provides endless opportunities to prank your stoner friends.

About Brian Ellis

With 6 years' experience in business journalism, Brian is the person we turn to for anything related to the business of cannabis. His news coverage spans topics including marijuana business and finance. Brian's work features on, and