Active Ingredient in Marijuana Causes Paranoia

Marijuana can increase short-term paranoia, new study led by Oxford University researchers says.

The study shows that the active compound in the drug THC (Δ9-tetrahydrocannabinol) can induce paranoia. The research also found that low self-esteem and changes in perception led to cannabis users feeling more paranoid than non-users.

Marijuana is a highly popular and an easily-accessible drug. About 48 percent of all people in the U.S. have used the drug at some point of their lives. According to recent estimates from Centers for Disease Control and Prevention, more teens are now smoking marijuana than cigarettes. Studies showing that cannabis can be effective in treating chronic pain have also added to the drug's popularity. The latest study shows that marijuana-use is not without any risks.

"The study very convincingly shows that cannabis can cause short-term paranoia in some people,' says Professor Freeman."But more importantly it shines a light on the way our mind encourages paranoia. Paranoia is likely to occur when we are worried, think negatively about ourselves, and experience unsettling changes in our perceptions."

The study included 121 participants between ages 21 and 50 years. All the participants had taken cannabis at least once in the past one year.  Researchers tested participants' paranoia levels via questionnaires and interviews.

Researchers found that all the study participants had reported feelings of suspicions and mistrust about other people.

In the next part of the study, participants were randomly given either an intravenous 1.5mg dose of THC or a placebo. Researchers again looked for signs of paranoia in the study subjects.

The team found that THC did increase paranoia in the subjects. About half of the participants on THC reported paranoia compared to 30 percent on placebo.

Researchers also found that THC-use was associated with poor short-term memory, anxiety and changes in perception of sights and sounds.

"Paranoia is excessive thinking that other people are trying to harm us. It's very common because in our day-to-day lives we have to weigh up whether to trust or mistrust, and when we get it wrong - that's paranoia. Many people have a few paranoid thoughts, and a few people have many paranoid thoughts," said Freeman of the Department of Psychiatry, according to a news release.

The study doesn't have any implication for criminal justice or legalization of marijuana, researchers said. Instead, the research shows that several factors are associated with feelings of paranoia in cannabis users.

The research was funded by the Medical Research Council (MRC) and is published in the journal Schizophrenia Bulletin.