As a general psychiatrist and addiction psychiatrist, I’m asked all the time about my opinions on cannabis, and what I think the pros and cons of marijuana use are for individual or public health. People want to know if it’s good for sleep, for anxiety reduction, and whether or not I think it should be legal or taken regularly to reduce their post-traumatic stress disorder symptoms. Be it in the office, or outside of it, there’s no paucity of curiosity and debate in our current environment about its use.
But what about for depression? Although anxiety and sleep are commonly cited reasons that people use cannabis, people also sometimes use it to lighten their mood, or to feel better. Another question that I hear, but which I see less addressed in the current literature, is also an important one: If I or a loved one suffer from depression, what impact does marijuana use have? Below, I’ll do my best to answer this question.
As of July 2021, marijuana is legal in 18 states, and many more states have approved its use for medical reasons. Every year sees more and more research into the utility and harms of cannabis-containing compounds and cannabinoid receptor targets for the treatment of psychiatric problems. Some states even allow medical marijuana cards to be issued for the treatment of depression.
So how can my answer be so definitively negative about its ability to improve depression? Well, as we all know, policy doesn’t always follow science.
Marijuana is not an efficacious treatment for depression
The best way for researchers to determine whether a treatment works is to do a randomized controlled trial, and to compare outcomes from an active treatment group with a group that received a placebo. If, on average, people are found to improve in a single-group study, it’s hard to know why the change happened; It could have been due to the intervention, a “placebo effect” or other study-related factors. A meta-analysis is also a useful way to find definitive, less-biased answers as it compiles data from numerous pre-existing studies.
An important meta-analysis, including 12 randomized trials and more than 1,500 patients with depression symptoms found no change in depression from pharmaceutical grade THC over 4-12 weeks of treatment. Observational and epidemiological studies using marijuana have also not found a positive long-term effect of cannabis use on the course and outcome of depression.
CBD is another component of marijuana which has less direct effects on the brain and carries a lower addiction risk than THC. Studies show that it might help reduce anxiety and marijuana withdrawal symptoms, but so far it has not been found to reduce depressive symptoms.
Cannabis may make psychiatric symptoms worse
We have known for a while that heavy cannabis use increases the risk of getting a psychotic disorder, especially in adolescents. It also can impair attention and memory, and trigger panic attacks. Most importantly, though, for the depression question, two large-scale, rigorous meta-analyses have found that extremely heavy use increases depression. One study determined that heavy cannabis use increases the odds of developing depressive symptoms later on. Another concluded that cannabis consumption in adolescence increases the risk of developing major depression and suicidality in young adulthood. Several expert panels now oppose the use of cannabis for major depressive disorder treatment.
The trickiness of self-medicating and addiction
So how do we explain the fact that so many people report mood benefits from consuming marijuana? For one, THC causes euphoria, just like other drugs of abuse. Second, it’s possible that some of these people are confusing mood improvement with alleviation of withdrawal symptoms. Just like other addictive substances, cannabis use is habit-forming. Frequent heavy use will change the brain over time such that withdrawal symptoms set in upon reduction or cessation of use. Symptoms of cannabis withdrawal include irritability, anxiety, poor sleep, loss of appetite, restlessness, depression, and these may start within a week of cessation. In people who frequently use marijuana, use relieves these symptoms which can trick them into thinking it’s helping their mood.
The bottom line
Current research does not support the use of marijuana for the treatment of depression, and people who report improvement in mood might just be relieving withdrawal. An alternate explanation is that, for a subgroup of people, marijuana actually is benefiting their depression. But, until the science can tell us which subgroup of people are most likely to benefit, it’s best to utilize strategies that have been proven to be effective and for which side effects are better known.