There is absolutely no link between chronic marijuana smoking during the teenage years and the development of mental health problems or other physical health problems later in life, a groundbreaking new study has found.

The study, which followed men from their teens into their 30s, was surprising to scientists, said psychology research fellow Dr. Jordan Bechtold at the University of Pittsburgh Medical Center according to a UPI report.

Scientists had expected to find some differences in the mental or physical health outcomes that were measured, but found absolutely none no matter what the frequency of marijuana use was, according to the report.

The study, which took place over a period of 20 years, contradicts previous studies that suggested chronic marijuana use during the teenage years resulted in a greater likelihood of developing symptoms of depression or other psychotic ailments. It was also theorized that marijuana had links to anxiety, headaches, high blood pressure, allergies, and other ailments.

A total of 408 people participated in the study, which began back when they were 14 years old in 1987 at public schools in Pittsburgh. These students were interview each year for 12 years, and then once more at the age of 36. The breakdown was about 54 percent black, 42 percent white, and 4 percent other.

In terms of usage, 46 percent used it only a low percentage of the time, 22 percent were chronic users, 11 percent smoked only as a teenager, and 21 percent smoked all the way from being a teenager into adulthood.

The purpose of the study was to truly understand the effects of marijuana on the health of individuals, especially with the growing debate in the U.S. about whether the drug should be legalized. The long-term effects of marijuana have been one of the major gray areas that opponents often cite as a reason to keep the drug illegal as several states push to legalize it. However, Bechtold warned that the issue was complex and one study wouldn’t be enough to settle the issue.