July 16, 2019 3 min read

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Scientists may have finally hit upon some answers for that curious phenomenon that anyone who has used marijuana has observed - either in others or themselves.

When using marijuana, some people can’t stop laughing. The smallest thing - a half-amusing television commercial, for example - can set them off into gales of wild laughter. They are happy.

Others, who smoked the very same weed, are not.

This second group becomes paranoid. You might see them constantly looking out the window, certain that bad news of some type is on its way. Worse, they may think what others are saying is somehow insulting or a threat to them.

What’s going on? Scientists recently tried to find an answer.

Related: New Findings Raise Doubts Whether Legal Weed Reduces Opioid Deaths

How the brain interacts with weed.

A new study from researchers at the University of Western Ontario in Canada examined the brain activity of rats who had been injected with THC, the chemical component in marijuana that causes the high feeling.

What they found is that how we experience marijuana may come down to the nucleus accumbens, the frontal region of the brain associated with reward behavior and the neurotransmitters dopamine and serotonin. THC seems to impact this area of the brain the most. When THC attaches primarily to receptors in the front area of the nucleus accumbens, it triggers euphoria but also stimulates further reward-related activity patterns in the neurons.

However, this region also is associated with “aversion processing,” in which potential threats are identified. If the THC attaches to receptors in the anterior of the nucleus accumbens, it can stimulate this area, leading to adverse symptoms of both the cognitive and emotional variety. It’s similar, the researchers said, to what is produced in people with schizophrenia.

Related: Researchers Find 'Recreational' Cannabis Customers Buy Weed to Sleep Better and Treat Pain

Why the same weed can affect people differently.

If you’ve felt paranoid after using a certain type of weed and wondered if you could just “get over it” or thought maybe it was because of your mood, the new research indicated that this is probably not the case.

“These findings are important because they suggest why some people have a very positive experience with marijuana when others have a very negative experience," Christopher Norris, one of the researchers, said in a statement about the research.

He went on to stay the research indicates that "because the reward and aversion are produced by anatomically distinct areas, the different effects between individuals is likely due to genetic variation leading to differential sensitivity of each area."

Genetic variation is obviously something people cannot control. It also means that different strains might impact users differently. The bottom line: whether you are happy or paranoid may simply come down to your DNA, not your personality type or mood that day.

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