Self-medicating for depression or anxiety with cannabis might not be a good idea in the long-term, new research at Colorado State University has found.

The conclusion comes from a study seeking to clarify how cannabis, particularly chronic, heavy use, affects neurological activity such as the processing of emotion. The study was performed using an in-depth, questionnaire-based analysis of 178 college-aged legal cannabis users in Colorado, where recreational use became legal in 2014. Several other states have since followed suit, and many others allow medical use.

“One thing we wanted to focus on was the significance of Colorado, the first state to legalize recreational cannabis, and its own unique population and use that occurs here,” said lead researcher Lucy Troup, assistant professor in the Department of Psychology at CSU.

The study was based solely on self-reported cannabis use, and aimed to draw correlations between depressive or anxious symptoms and consumption of the drug. Co-author Jeremy Andrzejewski led the development of a questionnaire called R-CUE (Recreational Cannabis Use Evaluation) which assessed users’ habits. This includes questions about whether users smoked the drug or used other stronger products like hash oil or edibles. Part of the researchers’ goal is to study biochemical and neurological reactions from higher-tetrahydracannabinol (THC) products available in the legal market, which can be up to 80-90 percent THC.

The team found that respondents with subclinical depression — who reported to use cannabis to self-treat their depressive symptoms — actually scored lower on anxiety symptoms than on depressive ones. In other words, they were more depressed than anxious. Self-reported anxiety sufferers were also found to be more anxious than depressed.

“If they were using cannabis for self-medication, it wasn’t doing what they thought it was doing,” explained co-author Jacob Braunwalder, a recently graduated student researcher in Troup’s lab.

The researchers point out that their findings don’t say that cannabis causes depression or anxiety, neither that it cures it. Andrzejewski says that it’s widely believed cannabis can help relieve feelings of anxiety, yet there is no research that supports this claim fully. Grad student and paper co-author Robert Torrence points to previous research that shows chronic use reduces the levels of natural endocannabinoids in the brain, known to play a role in mood and memory regulation.

But largely due to federal regulation, under which cannabis is considered a schedule I drug, the public’s perception of cannabis action on the brain is usually based on “mythos“, Braunwalder said.

“We want to add more information to the entire body of research,” he added.

The team believes their findings illustrate the need for further study on how cannabis influences the brain, especially in light of legalization and the more widespread use it could see in the future.

“There is research to suggest that cannabis can help with anxiety and depression in the beginning, but it has the reverse effect later on,” said Torrence, a U.S. Army veteran who is interested in studying cannabis’ effectiveness in treating PTSD.

The study relied on self-reporting as there are no CSU research labs with licensing and security measures in place to allow for administration of the drug for research. In the future, the researchers want to refine their results and concentrate on respondents’ level and length of exposure to legally available high-THC products like concentrates and hash oils, around which there has been little scientific inquiry.

“It is important not to demonize cannabis, but also not to glorify it,” Troup said.

“What we want to do is study it, and understand what it does. That’s what drives us.”

The full paper “The relationship between cannabis use and measures of anxiety and depression in a sample of college campus cannabis users and non-users post state legalization in Colorado” has been published in the journal PeerJ.

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