A study published in the Journal of Alzheimer's disease indicates that smoking cannabis can increase the age of the brain by an average of three years. The drug was found to age the brain by 2.8 years, making it worse for the mind than both bipolar disorder or attention deficit hyperactivity disorder. In schizophrenics, the magnitude of aging was found to be even more significant, with the average found to be four years.

According to the New York Post, researchers analyzed 62,454 brain scans from 31,227 people for the study. Scans were collected during both rest and concentration from people aged between nine-month-old and 105-year-old to determine what factors contribute to brain aging — which is defined as the reduced blood flow through the organ. Reduced blood flow has also been linked to strokes and dementia in the past.

Researchers then analyzed this blood flow through 128 regions of the brain to determine how old the individual was using the person's actual age as a yardstick to measure how much the organ aged when the person smoked cannabis.

Speaking about the findings, lead study author Dr. Daniel Amen, the founder of Amen Clinics, warned against increased use of marijuana. "The cannabis abuse finding was especially important, as our culture is starting to see marijuana as an innocuous substance," he said. "This study should give us pause about it."

Sachit Egan, another author from Google, one of the partners, also spoke about the implications of their findings. "The results indicate that we can predict an individual’s age based on patterns of cerebral blood flow," he said. "Additionally, groundwork has been laid to further explore how common psychiatric disorders can influence healthy patterns of cerebral blood flow."

The results from the study also seem to show that bipolar disorder ages the brain by 1.6 years and attention deficit hyperactivity disorder ages the organ by 1.4 years, significantly smaller compared to the effects of cannabis smoking. Surprisingly, no link was found between depression and brain aging.

"Based on one of the largest brain imaging studies ever done, we can now track common disorders and behaviors that prematurely age the brain," Amen added. "Better treatment of these disorders can slow or even halt the process of brain aging."