By Lisa Rapaport
(Reuters Health) - - More than two in five teens who use marijuana experience psychotic symptoms like hallucinations, paranoia and anxiety, a U.S. study suggests.
Marijuana use during adolescence has long been linked to an increased risk of developing psychotic disorders like schizophrenia as well as other mental health problems, researchers note in JAMA Pediatrics. While previous research has found otherwise healthy adult marijuana users can experience psychotic symptoms, less is known about the potential for this to occur among teens.
For the current study, researchers surveyed 146 teen marijuana users, ages 14 to 18. Forty, or 27 percent, reported hallucinations while using the drug and 49, or 34 percent, said they had experienced paranoia or anxiety.
"This is yet more reason for parents to keep their kids away from marijuana," said study co-author Dr. Sharon Levy, director of the adolescent substance use and addiction program at Boston Children's Hospital.
Teens in the current study were 17 years old on average, and almost half of them said they used marijuana at least monthly during the past year.
Compared to youth who said they had only tried marijuana once or twice, adolescents who used it every month were more than three times more likely to experience hallucinations, paranoia or anxiety.
Almost one in four teens in the study reported symptoms of depression.
Adolescents with depression symptoms were more than three times more likely to experience paranoia and anxiety and 51 percent more likely to report hallucinations than teens without symptoms of depression.
And 26 participants, or 18 percent, had symptoms of anxiety. Compared to teens who didn't have anxiety symptoms, those who did were more than twice as likely to experience paranoia and 84 percent more likely to experience hallucinations.
The study wasn't designed to prove whether marijuana directly causes hallucinations, paranoia or anxiety or whether mental health problems like depression might play a role in this relationship.
"We don't know if the greater exposure to marijuana over time made the brain more susceptible to psychotic symptoms, whether kids who experienced psychotic symptoms became more likely to continue to use marijuana or if some third factor, such as depression, made kids both more likely to use marijuana heavily and also more susceptible to psychotic symptoms triggered by marijuana," Levy said by email.
"Regardless of which of these explanations is most accurate, there is clearly an interaction between marijuana use and brain function," Levy added.
Some previous research suggests that effects of marijuana use may be more pronounced in teens than adults because adolescence is a period of rapid brain development, said Dr. Koen Bolhuis, a specialist in child and adolescent psychiatry at Erasmus University Medical Centre in Rotterdam, the Netherlands.
It's also possible that some teens who use marijuana might have unmet mental health needs, Bolhuis, who wasn't involved in the study, said by email.
"It is important for parents to have an open conversation with their children about their cannabis use," Bolhuis said by email. "Cannabis use might be an indication of pre-existing, underlying mental health difficulties."