Marijuana is one of the most widely used drugs in the United States, and many studies have linked chronic use during adolescence to physical and mental health issues in later life. However, a new study has challenged these findings and suggests that chronic marijuana use by adolescents is not associated with an increased risk of adverse long-term health effects.
Researchers from Rutgers University and the University of Pittsburgh Medical Center tracked more than 400 males from adolescence into the mid-30s to review the effects of marijuana over more than two decades. Published in the American Psychological Association's journal "Psychology of Addictive Behaviors" in August 2015, the study obtained data from the Pittsburgh Youth Study, a long-range project that began in the late 1980s as a means to analyze the development of physical, mental and social problems amongst male public school students.
The researchers placed the men into four groups based on self-reported marijuana use: low or no marijuana use (46 percent), marijuana use limited to adolescence (11 percent), marijuana use commencing in late adolescence and continuing through adulthood (21 percent) and early-onset chronic marijuana use (22 percent). Early-onset chronic users reported higher marijuana use, which rapidly increased during adolescence and peaked at the age of 22, when marijuana was used for more than 200 days per year, on average. The men were surveyed every six months for the first 2.5 years and then annually for 10 years until the age of 26. A follow-up survey was conducted in 2009-2010 when the men were 36 years old.
The researchers expected to find a link between adolescent marijuana use and health issues, such as psychotic symptoms, depression, cancer, asthma or respiratory problems in later life. However, the study revealed no significant differences in any of the four groups in terms of the prevalence of mental or physical health issues in the mid-30s, irrespective of the amount or frequency of cannabis used. It also revealed no differences based on race or ethnicity.
The findings suggest that marijuana is more beneficial than harmful and help to discredit claims that marijuana is bad for teens. They lend weight to the argument that marijuana should be removed from Schedule I of the Controlled Substances Act, a category reserved for the most dangerous drugs. Marijuana's classification as a Schedule I drug has been hotly debated for decades, with medical marijuana advocates pointing to the growing body of evidence demonstrating marijuana's efficacy as a treatment for a variety of health complaints.
Given that each day more than 3,000 teenagers in the United States use marijuana for the first time, a clear understanding of the long-term effects of marijuana must be established as more states consider moving towards permissiveness. While critics remain concerned that the legalization of medical marijuana will lead to a rise in marijuana use, especially among teenagers, research carried out by Columbia University Medical Center in New York and published in the journal "The Lancet" in June 2015 revealed a decrease in teen marijuana use in states that have legalized medical marijuana.