The age and frequency of marijuana usage during adolescence could cause depression and negatively affect educational performance, according to a study published in the Addiction journal on July 25, the University of Pittsburgh Medical Center reported.
“We know that cannabis use in adolescence is associated with outcomes like lower educational level and difficulties with mood and depression, but through this long-term study, we’ve been able to provide a much deeper insight into this relationship, showing that certain characteristics of use may be more important than others,” said Erika Forbes, a professor of psychiatry, psychology and pediatrics and the lead author of the study.
Researchers from the Department of Psychiatry at the University of Pittsburgh School of Medicine and Pitt Department of Psychology conducted the study. The researchers analyzed 158 young men who were a part of The Pitt Mother & Child Project (PMCP), a Pittsburgh study of males at risk of being anti-social based on low income, family size and gender. The young men were interviewed at age 20 about their annual marijuana usage. Their brains were also scanned to assess connectivity in the reward circuit. The young men also completed questionnaires at ages 20 and 22 that measured their depression and education.
The researchers examined the frequency of marijuana usage in the young males from age 14 to 19. The results revealed that the young males who began using the drug at around 15 to 16 years old and dramatically increased usage by 19 had the most dysfunction in their brain reward circuitry, the highest rates of depression, and lowest academic achievements.
“We expected to see that the young men who had a high, consistent level of marijuana use would have differences in brain function. However, it turned out that those who had an increasing pattern of use over their teens had the biggest differences,” Forbes said.