Smoking weed can cause paranoia, though not for everyone and not all the time. And the reason may be that you're predisposed to negative thoughts.

In 2014, Researchers at Oxford University concluded what was - at the time - the largest study ever conducted on the effects of THC. They were particularly interested in the relationship between paranoia and cannabis use. After working with a group of 121 volunteers, they found that the same chemical that makes people high also makes some people panic.

"The results were clear: THC caused paranoid thoughts," the study's' author Daniel Freeman told The Guardian."Half of those given THC experienced paranoia, compared with 30 percent of the placebo group: that is, one in five had an increase in paranoia that was directly attributable to the THC."

But it's not really THC's fault so much as the way certain brains are wired. Every volunteer who consumed THC experienced what Freeman calls "'anomalous experiences': sounds seemed louder than usual and colors brighter; thoughts appeared to echo in the individuals’ minds; and time seemed to be distorted."

These changes in perception can be unsettling for some people, especially those who are already uncomfortable in unexpected situations.

"Worry leads us to the worst conclusions," Freeman explained. "So when we try to make sense of the anomalous experiences – when we try, in other words, to understand what’s happening to us – the world can appear a weird, frightening and hostile place. Hence the paranoia."

To avoid any negative cannabis experiences, you might want to go somewhere where you feel comfortable and relaxed before you smoke-up so that your sesh isn't ruined by negative thinking or anxiety. You can also speak to your bud-tender about exactly what you want from your cannabis experience so that they can help you pick the right strains for your needs. And if you are prone to panicky thoughts, it's probably best to avoid high-THC strains.