Like the chicken or the egg, marijuana use and psychosis can go both ways, a new study has revealed. While using marijuana has been linked to the development of psychotic symptoms in teens, new findings revealed that the reverse could also be true after a new Dutch study linked psychosis in teens to later pot use.

"We have focused mainly on temporal order; is it the chicken or the egg? As the study shows, it is a bidirectional relationship," the study's lead author Merel Griffith-Lendering, a doctoral candidate at Leiden University in The Netherlands, told Reuters Health.

Scientists have previously found that psychosis is an effect of cannabis use, but some questioned whether it was marijuana that increased the risk of mental illness or whether people were using marijuana to ease their psychotic symptoms such as confusion, hallucinations, delusions and having a lack of self-awareness.

Dr. Gregory Seeger, medical director for addiction services at Rochester General Hospital in New York, told Reuters that the "interesting" thing about the new study is that it appears that "both processes are going on at the same time."

He pointed out that researchers were particularly interested in the effect of tetrahydrocannabinol (THC), the active property in marijuana, on an adolescent's developing brain, adding that those who have a family history of schizophrenia and psychosis were more sensitive to the toxic effects of THC.

Dutch researchers who wanted to find out whether pot or psychosis came first studied 2,120 Dutch teenagers. The teens filled out surveys that asked them about their past marijuana use at the age of 14, 16 and 19. Researchers also gave participants psychosis vulnerability tests that determined their ability to concentrate, their feelings of loneliness and whether they hallucinate or see things that other people don't.

Griffith-Lendering and her team found that about 44 percent or 940 teens in the study reported smoking marijuana, and that there was a bidirectional link between using marijuana and psychosis.

For instance, researchers found that using marijuana at the age of 16 was linked to psychotic symptoms three years later, and having psychotic symptoms at the age of 16 was linked to marijuana use at age 19.

Researchers said the findings held true even when they accounted for family history of mental illness, alcohol use and tobacco use.

Researchers said they could not quantify the exact risk young marijuana users were likely to show psychotic symptoms later on, or whether one causes the other.

However, Griffith-Lendering and her team conclude that genetics may also play a role between pot use and psychosis.

"We can say for some people that cannabis comes first and psychosis comes second, but for some people they have some (undiagnosed) psychosis (and) perhaps cannabis makes them feel better," said Dr. Marta Di Forti, of King's College, London, who was not involved with the new study, according to Reuters.

The researcher who has studied the link between marijuana use and psychosis said that she believes that marijuana is not a cause but a risk factor for psychosis.

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