Early teen exposure to cannabis may damage brain

According to experts, cannabis, the most common illicit drug by adolescents, suppresses activities in the brain that control the level of consciousness.

The study found chronic cannabis users who started smoking before their 15th birthday were at an elevated risk of neuropsychological problems compared to those who abused the street drug at the later stage.

Lead researcher Dr. Maria Fontes stated, “We found that early-onset, but not late-onset, chronic cannabis users had deficits in their cognitive functioning.

"We know that adolescence is a period in which the brain appears to be particularly vulnerable to the neurotoxic effects of cannabis.

“Brain imaging studies have shown that the brain before the age of 15 is still developing and maturing, so exposure to cannabis during this period may be more harmful and lead to lower mental flexibility.”

Study details
In order to determine whether early exposure to cannabis use can cause damage to teen’s brain, the researchers carried out a study.

They enrolled 104 young chronic cannabis users. Among them, 49 had started abusing the drug before hitting age 15 (early-onset users) while the remaining started smoking pot after crossing 15 years (late-onset users).

The early users had smoked cannabis for nearly 10.9 years and their lifetime consumption of the drug translated into 6,790 joints each.

On the other hand, the late users had abused the drug for an average of 8.7 years with their consumption of the illicit drug equating to 5,160 cigarettes each. The study also recruited another 44 teens who didn't use cannabis.

The volunteers participated in a series of mental exercises. The tests were designed to assess the neurological impact of early cannabis use.

“Brain imaging studies have shown that the brain before the age of 15 is still developing and maturing, so exposure to cannabis during this period may be more harmful and lead to lower mental flexibility.”--Lead researcher Dr Maria Fontes.

Outcome of the study
The study found no significant differences in IQ levels of the three groups. However, early abusers of cannabis fared poorly in tasks involving executive functioning, concentration and perseverance compared to the late users and the control group.

Early users of cannabis made more mistakes and were able to complete lesser categories in the card-sorting test. However, the score card of non-users and those who had acquired the drug habit later on was same.

Lead researcher Dr Maria Fontes stated, “It is possible people who start to use cannabis at a later age may use different neural networks, and be able to compensate for their cognitive deficits more than people who started using cannabis at an earlier stage of brain development.”

The study has been published in the 'British Journal of Psychiatry.'