Can Cannabis Control Depression?

Marijuana is under investigation as a potential treatment for depression -- as well as other mental illnesses. What are the positives and negatives of cannabis as a depression therapy?

Untreated and inadequately controlled depression is a big problem. In 2016, 16.2 million American adults experienced at least one major depressive episode, according to the National Institute of Mental Health. Approximately 37% did not receive any kind of professional treatment –- no counseling, no antidepressants, no mental health evaluation. That’s nearly 6 million people living, working and parenting under a cloud of depression.

Additionally, somewhere between 10 and 30% of those who receive treatment for depression do not improve or only improve partially. Many eventually quit their antidepressant medication and therapy due to frustration.

Could cannabis help these patients? At least one doctor thinks so. Jordan Tishler, MD, a Harvard-trained internal medicine physician who currently serves as the president of the Association of Cannabis Specialists and treats patients via his private practice, Inhale MD, recommends cannabis as a substitute for or adjunct to prescription antidepressants.

“Cannabis can be a good substitute [for medication], but only under certain circumstances,” Dr. Tishler says.

Marijuana & Mood: What We Know – and What We Don’t

To date, scientific research regarding the effects of Cannabis sativa (marijuana) on mood have been mixed. Some studies suggest that marijuana usage has a negative impact on mood; that cannabis use over time can cause or worsen depression. Other studies suggest that cannabis can alleviate depression.

The problem with the research is that it’s incomplete. Under US federal law, marijuana is still a Schedule I drug and therefore subject to strict rules. Researchers can’t, for instance, give subjects cannabis. “The best they can do,” Dr. Tishler says, “is have them bring their own cannabis or talk about their cannabis use.”

Such studies don’t allow researchers to control or compare strains of cannabis, and make it difficult to accurately assess dosage. That’s a problem because “that’s exactly where the devil lies in this particular discussion,” Dr. Tishler says.

The only source of marijuana approved for medical studies is under control of the National Institute for Drug Abuse (NIDA) at the University of Mississippi. And it requires researchers to complete a mountain of paperwork just to have NIDA consider such a request.

One researcher who requested marijuana from NIDA — and was approved — is Sue Sisley, MD, the president and principal investigator at Phoenix’s Scottsdale Research Institute, arguably the nation’s foremost private research institute investigating medicinal uses of marijuana.

Sisley echoed Tishler’s concerns. Speaking at a panel on marijuana at the American Psychiatric Association Annual Meeting in New York City earlier this month, she mentioned one problem with NIDA’s marijuana once it arrived at her offices. The marijuana had not only the leaves, but stems and other parts that are considered non-therapeutic. In other words, much of the marijuana sent to her via FedEx was useless.

But that wasn’t the worst of it. Sisley added that she suspected the marijuana was bagged years ago and not stored under proper conditions in Mississippi, because mold was present.

A 2007 study published in the Journal of Neuroscience examined the impact of cannabis on rats, concluding that tetrahydrocannabinol, or THC, cannabis’ psychoactive chemical, has antidepressant effects at low doses. High doses of THC, however, can worsen depression, at least in rats.

Data on cannabis’ effect on human mood is sparse. “We don’t have clean data in patients with depression. We have data from people who suffer from multiple sclerosis or other diseases, such as epilepsy,” says Gabriella Gobbi, MD, PhD, CSPQ, a psychiatrist in the Mood Disorders

Program at the McGill University Health Centre in Montreal. In other words, some researchers who were assessing the effectiveness of marijuana to treat multiple sclerosis, epilepsy and other diseases asked subjects about the drug’s impact on their mood, but no one has formally studied cannabis as a treatment for depression.

“We need to do randomized clinical trials in people with depression,” Dr. Gobbi says. Such trials would compare cannabis versus a placebo, and assess the treatment’s effect on depressive symptoms.

Available human and animal studies suggest that adolescents and adults respond differently to cannabis. “In animal experiments, it’s very clear: Cannabis given during adolescence every day increases the risk of developing depression in adulthood,” Dr. Gobbi says. “If you start cannabis later in life, this risk to develop depression is less important.”

The Risks & Benefits of Using Cannabis to Treat Depression

Although cannabis is known for inducing euphoria, “it’s a relatively weak antidepressant,” Dr. Tishler says. Therefore, it’s not likely to be an effective stand-alone treatment for many people with depression. Cannabis can also trigger mania or psychotic episodes in people with bipolar depression or a family history of psychosis or bipolar depression.

Other risks of cannabis use include “the acute risk of impaired judgment and driving,” says Kevin Hill, MD, MHS, director of the Division of Addiction Psychiatry at Beth Israel Deaconess Medical Center and author of Marijuana: The Unbiased Truth About the World’s Most Popular Weed. Risks from chronic use, he says, include “worsening depression or even addiction.”

Dr. Tishler tries to control risks by carefully selecting patients for treatment. “If a patient comes in and says, ‘Doc, I’m on a starter dose of Zoloft (sertraline), 25 milligrams, and it’s working but I want to get off it because of side effects,’ then I think cannabis is reasonable substitution,” he says. “But if somebody is on a high dose – 100 milligrams or more –- then I don’t think it’s reasonable or responsible to try to do a substitution.” Instead, he might suggest cannabis as an adjunct to prescription antidepressant medication.

“Adding cannabis on top of a selective serotonin reuptake inhibitor (SSRI) can let some of the joy of life come back,” Dr. Tishler says. “The other thing we should mention is that SSRIs, generally speaking, are terrible for one’s libido. Cannabis is good for libido.”

Medical professionals agree that it is not a good idea to self-treat depression with cannabis. Dr. Tishler says that patients who are considering using cannabis should consult with a physician. “Even physicians who don’t know very much about cannabis, assuming they are open-minded to it, still know more about human biology and healthcare” than the clerk at the nearest weed shop, he says.

Dr. Hill says it’s critical for patients to discuss their mood openly with their physicians. “Decisions about how to treat depression should be made as part of a conversation between a patient and a doctor who knows them well,” Dr. Hill says. “Patients should collaborate with their physician to make sure that evidence-based treatments have been given a chance to work before turning toward treatments like cannabis that have no evidence behind them.”