Study: how marijuana causes paranoia

In what is deemed the largest and most in-depth study of the effects of the main ingredient in marijuana, researchers say they have identified the psychological factors that can lead to feelings of paranoia among users of the drug.

The research team, led by Prof. Daniel Freeman of the University of Oxford in the UK, recently published their findings in the journal Schizophrenia Bulletin.

Marijuana, also known as cannabis, is a drug that is produced from the plants Cannabis sativa or Cannabis indica. The main active ingredient in marijuana is delta-9-tetrahydrocannabinol (THC), which is responsible for the majority of the drug’s psychological effects, such as hallucinations and delusions.
cannabis leaf
Researchers suggest that THC - the main active ingredient in marijuana - causes certain negative feelings and changes perceptions that induce paranoid feelings among users of the drug.

Past research has indicated that marijuana use can induce paranoia - which Prof. Freeman describes as “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,” he explains." Many people have a few paranoid thoughts, and a few people have many paranoid thoughts."

For the study, Prof. Freeman and colleagues tested the effects of THC on 121 participants ages 21-50 in order to see whether the compound triggers paranoid feelings and how it does this. All participants had used cannabis at least once previously and had no history of mental health conditions.

Two thirds of participants were injected with THC at a dose equivalent to a strong joint, while a third of participants were injected with a placebo. The researchers note that they chose to inject the participants with the compound as it ensured they all had similar levels of THC in their bloodstream. The researchers report that the effects of THC on participants lasted for 90 minutes.
THC causes ‘negative feelings and changes in perception that induce paranoia’

Results of the study revealed that among participants who were injected with THC, around 50% reported paranoid thoughts, compared with 30% of participants who received the placebo. The researchers note that as the compound left the bloodstream, feelings of paranoia reduced.

The team found that THC also induced anxiety, worry, reduced mood, negative thoughts about oneself, changes in perception - including the report of louder noises and clouds being brighter - and altered their perception of time. Using a statistical analysis, the researchers found that it may be these negative feelings and changes in perception that cause paranoid feelings among marijuana users.