A new study is challenging whether pot smoking during adolescence could really lead to decline in intelligence. Smoking marijuana could be linked to something else that is behind a brainpower effect reported in some past studies, as per the study published in the Proceedings of the National Academy of Sciences.

Joshua Isen, a psychology lecturer at Loyola Marymount University in Los Angeles and an author of the new study, said that the other factor is not known yet, “But an adolescent at risk for smoking pot is probably going to show this IQ drop regardless of whether he or she is actually smoking marijuana”.

Some previous studies reported that pot smoking could harm the development of an adolescent brain. According to experts, it is not easy to conduct experiments on teen pot smoking and expose adolescents to marijuana just to compare results. Researchers can only use data of people who smoke marijuana on their own.

For the new study, Isen and other researchers collected data from two studies of twins and examined them. They analyzed data on about 3,066 volunteers who received a battery of intelligence tests when they were between nine to 12 years of age and again at ages 17 to 20.

They compared changes in tests scores and checked if those trajectories were different for users who smoked marijuana than those who didn’t. Most of the tests did not show any difference between the two groups, but the researchers noticed that the marijuana-user participants did fare more poorly than their counterparts.

According to the study, the data collected by the researchers did not reveal anything about if smoking pot harmed test scores. If previous researchers were correct, then the researchers would get data showing poorer trends for marijuana users.