Study claims teens who smoke weed have worse grades

The odd "harmless" joint may also heighten emotional problems, say scientists.

They warned that it is not unusual for a young teenager to smoke dope "only a few times" before showing signs of withdrawal and worsening mood.

The study found that using cannabis just once or twice a month was associated with worse school performance and emotional distress for teenagers.

The more frequently teens used dope, the more likely they were to report emotional distress and other social or academic problems, according to the findings published in the journal Pediatric.

Study leader Dr. Ryan Sultán said: “While previous studies have focused on the effects of frequent cannabis use among teens, our study found that any amount of cannabis use at all may put kids at risk of falling behind in school, and the kids using most often may have the greatest risk.

“A few ‘harmless’ joints can snowball into real academic consequences.

"Teens using it regularly often struggle to focus, miss school, and may lose interest in their future plans.”

While use of many substances is at record lows among American youths, he says cannabis remains an exception.

Roughly one in five high school students currently use cannabis, and around 6% of 12th graders use it daily - a rate that has increased over the past decade.

Dr. Sultán, an Assistant Professor of clinical psychiatry at Columbia University Vagelos College of Physicians and Surgeons in New York, said: “The real-world impact can be dramatic.

“It’s not uncommon for a young teen to smoke marijuana only a few times before showing signs of withdrawal and worsening mood.”

Scientists are especially concerned because today’s cannabis products contain two to three times more THC - the ingredient that causes a "high" - than in the past, making them more potent.

Previous research has shown that using cannabis during adolescence, when the brain is still developing critical neural connections, may have lasting effects on cognitive functions that are critical to academic performance.

Study co-author Dr. Tim Becker, a child psychiatrist at Weill Cornell Medicine, New York said: “A teenager’s brain is still developing the circuits for learning, self-control, and emotional regulation.

“Using cannabis, even casually, during these critical growth periods interferes with those processes and can derail normal development.”

The new study analyzed data from a nationally representative survey of more than 160,000 American students.

More than a quarter of them reported using cannabis, while less than 20% reported monthly or less frequent use and much smaller percentages said they used cannabis weekly or almost every day.

Adolescents who used cannabis once or twice a month reported higher rates of depression-like symptoms, anxiety, and impulsive behavior than those who abstained.

Near-daily users were almost four times as likely to have poor grades and were frequently disengaged from school activities.

The associations were even stronger for younger cannabis users, according to the findings.

Experts recommend that parents and caregivers should have "frank, non-judgmental" conversations with teenagers about cannabis "early and often".

Dr. Sultán said: “Make sure they understand that 'natural' doesn’t mean 'safe.'”

He added: “Parents also need to keep an eye out for warning signs like declining grades, mood changes, or loss of interest in hobbies – and consider that cannabis could be a factor.”