Many who have tried marijuana often said that they've suffered from short-term paranoia. It has now been proven by British scientists that taking weed can actually cause a person to be paranoid for a short time due to the ingredient tetrahydrocannabinol (THC).

Paranoia is a common side effect of marijuana and a study conducted by the University of Oxford researchers say that there are psychological factors involved. According to lead researcher Daniel Freeman, THC in weed causes increased paranoia in others because it magnifies the feelings of worry.

In their study, the researchers tested the effect of marijuana THC to three groups. One group was given a THC dose via injections and another was given a placebo. The THC dose was equal to the amount of taking a good dose of weed.

They found out that 50 percent of those who were injected with marijuana THC got paranoid. The short-term paranoia in the subjects declined after the active ingredient, THC, left their bodies, CBS News reports.

Marijuana-induced paranoia is also caused by a person's state of mind. Bustle reports that THC affects everyone's endocannabinoid system differently. When the cannabinoid interacts with the amygdala of the brain which is responsible for paranoia, stress and fear, the communication of the brain and body is temporarily changed.

Furthermore, marijuana and THC affects everyone differently which is why some people get more paranoid than others. However, this is not caused by taking of any of the popular weed strains, sativa or indica. The paranoia may also be coming from its illegality.

In some states where marijuana is still illegal, some users are known to get more paranoid with using it. Marijuana users with advanced ages may also be more paranoid when using weed than their younger counterparts. The outlet adds that people might have different reactions to THC when they get older.