A pattern of increasing marijuana use in adolescence may lead to higher rates of depression and lower educational accomplishments, according to a new study led by researchers from the University of Pittsburgh published in the journal Addiction. Researchers analyzed 158 boys and young men from Pittsburgh who completed questionnaires about their marijuana use and psychosocial outcomes like level of education and depression, and had an MRI brain scan. While researchers expected to see the worst outcomes in boys who reported consistently high marijuana use, boys who started occasionally using cannabis around 15 or 16 years old and gradually increased use by age 19 actually had the highest rates of depression, the lowest educational achievements, and the greatest dysfunction in brain reward circuitry. Dysfunction in the brain reward circuitry is an important measure as it suggests that these adolescents have impaired responses to things that are commonly seen as positive stimuli.
“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,” said lead author Erika Forbes, PhD. “Though the results do not show a direct causal link, it’s important to note that even though most people think marijuana isn’t harmful, it may have severe consequences for some people’s functioning, education and mood,” Forbes said. “While that may seem unimportant at age 20, the level of education you receive will likely have a huge effect on your quality of life and socioeconomic status later in adulthood.”
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