The usefulness of medical marijuana for the treatment of mental illness and disorders such as depression, bipolar disorder, anxiety, and schizophrenia is an open question today. There have been only a few really good studies on this issue, and their findings are decidedly mixed.
So let’s dive into the question and see if medical marijuana can help the symptoms of mental illness, or is it more likely to cause harm?
The reason this is a very complex issue is because, unlike medical marijuana for chronic, debilitating pain, there’s a lot of additional factors that must be taken into account when studying mental illness and a psychoactive substance like marijuana. We’re just going to examine marijuana for the use of depression, anxiety, and bipolar symptoms in this article, because those are the populations that have had the greatest number of research studies done.
Marijuana for Depression & Anxiety
Here’s what one recent study found when combing the recent research literature to better understand it:
Results from studies that have focused on recreational users and/or young adults are quite variable; some show a negative association between marijuana use and anxiety/depression (e.g., Denson & Earleywine, 2006; Sethi et al., 1986; Stewart, Karp, Pihl, & Peterson, 1997), others a positive association (e.g., Bonn-Miller, Zvolensky, Leen-Feldner, Feldner, & Yartz, 2005; Hayatbakhsh et al., 2007; Scholes-Balog, Hemphill, Patton, & Toumbourou, 2013), and still others no association (e.g., Green & Ritter, 2000; Musty & Kaback, 1995). Such a diverse pattern of results suggests that other factors may also interact with marijuana use to affect anxiety and depression. (Grunberg et al., 2015).
That’s a fair amount of research — but none of it really conclusive, and much of it contradictory.
That is characteristic of this area of research — complicated, with results often at odds with other research.
These researchers examined 375 University of Colorado students over a 3-year period to track their marijuana use, as well as depression and anxiety symptoms. They also understood that the complexity of human behavior requires a more nuanced approached to an analysis of marijuana use. “The temperament dimension of harm avoidance (HA) is particularly relevant for understanding anxiety and depression as it is characterized by heightened apprehension, shyness, pessimism, and inhibition of behaviors. Given these biases, it is not surprising that HA is positively associated with both anxiety and depression.” So the researchers ensured they also measured temperament. ((Notice, too, that the researchers are looking at recreational marijuana use and not medically-prescribed marijuana use. That’s because whether you get your marijuana from a prescription pad or from a local, informal source, marijuana is largely the same. It is equally as powerful and going to have very similar effects when taken regularly. And because marijuana isn’t recognized by most practitioners as a legitimate treatment for depression symptoms, it’s hard to do research on it.))
It is also important to consider that the simple relations we observed between marijuana use and depression symptoms differed from those obtained in the more complex models. That is, when only marijuana use was considered, results suggest a positive association between marijuana use and depression. […] [Ed. – This means that greater marijuana use was correlated with greater depressive symptoms.]
However, in the regression models that prospectively predict anxiety/depression and also include [multiple personality factors and temperament] interactions, and baseline anxiety or depression, marijuana use was not an independent predictor of depression symptoms. Moreover, in the models involving [novelty seeking], marijuana use negatively predicted depression symptoms (and anxiety).
These differing patterns of results first demonstrate the importance of measuring the effects of marijuana within the context of other factors known to affect anxiety and depression, as well as prior symptoms of anxiety and depression. The results might also indicate a complex causal relation between marijuana use and depression in which initial symptoms of depression facilitate marijuana use, which subsequently decreases depression (Grunberg et al., 2015).
As you can see, if you simply measure marijuana use and depressive or anxiety symptoms, you might walk away from your study believing that the two share some sort of causal relationship. But as Grunberg et al. found, when you dive deeper into patient histories and personality factors — especially temperament — that relationship goes away. And, in fact, marijuana use might actually help improve depressive symptoms.
What Happens When You Don’t Take the Complexity of These Disorders into Account?
One such study that didn’t look into personality factors or temperament was conducted more recently by Bahorik et al. (2017). As they note, “Marijuana is frequently used by those with depression, yet whether its use contributes to significant barriers to recovery in this population has been understudied.” That’s very true.
So the researchers examined the marijuana use and depression and anxiety symptoms of 307 psychiatry outpatients with depression; assessed at baseline, 3-, and 6-months on symptom (PHQ-9 and GAD-7), functioning (SF-12) and past-month marijuana use for a substance use intervention trial.
What they found was that a considerable number of patients used marijuana within 30-days of baseline — just slightly over 40%. What else did they find? “Depression symptoms contributed to increased marijuana use over the follow-up, and those aged 50+ increased their marijuana use compared to the youngest age group. Marijuana use worsened depression and anxiety symptoms; marijuana use led to poorer mental health functioning.” In addition, they found — surprisingly — that medical marijuana was associated with poorer physical health functioning. ((It could be that those in poorer physical health need medical marijuana to help alleviate a chronic pain or other health condition.))
The researchers concluded that, “marijuana use is common and associated with poor recovery among psychiatry outpatients with depression. Assessing for marijuana use and considering its use in light of its impact on depression recovery may help improve outcomes (Bahorik et al., 2017).”
What about Marijuana for Bipolar Disorder?
Another study looked at the benefits and drawbacks of marijuana for bipolar disorder, because it is the most widely used illicit substance by people with this disorder. Does it help (or hurt) not only symptoms associated with bipolar I disorder, but also cognitive functioning?
The study consisted of 74 adults: 12 with bipolar disorder who smoke marijuana (MJBP), 18 bipolar patients who do not smoke (BP), 23 marijuana smokers without other Axis 1 pathology (MJ), and 21 healthy controls (HC), all of whom completed a neuropsychological battery. Participants also rated their mood 3 times daily, as well as after each instance of marijuana use over a 4 week period.
The researchers found that although the three groups each exhibited some degree of cognitive impairment relative to healthy controls, no significant differences between the two bipolar disorder-diagnosed groups were apparent, providing no evidence of an additive negative impact of bipolar disorder and marijuana use on one’s thinking abilities.
Additionally, the mood ratings indicated alleviation of mood symptoms in the MJBP group after marijuana use; MJBP participants experienced a substantial decrease in a composite measure of mood symptoms. As the researchers note, “Findings suggest that for some bipolar patients, marijuana may result in partial alleviation of clinical symptoms. Moreover, this improvement is not at the expense of additional cognitive impairment” (Sagar et al., 2016).
This research actually helps support previous research conducted by Gruber et al. in 2012. In their study of 43 adults, they found “Significant mood improvement was observed in the MJBP group on a range of clinical scales after smoking MJ […] Notably, total mood disturbance, a composite of the Profile of Mood States, was significantly reduced in the MJBP group” (Gruber et al., 2012).
Further, while the MJBP group reported generally worse mood ratings than the bipolar group prior to smoking marijuana, they demonstrated improvement on several scales post-marijuana use as compared to bipolar, non-marijuana participants. These data provide empirical support for anecdotal reports that marijuana acts to alleviate mood-related symptoms in at least a subset of bipolar patients and underscore the importance of examining marijuana use in this population. (Gruber et al., 2012).
So Does Marijuana Help with Depression, Anxiety, & Bipolar Disorder?
The data is decidedly mixed, and it’s not at all clear whether marijuana would help someone with a mental health condition or not. I suspect that, in the end, it would come down to an individual’s unique reaction, similar to how each individual reacts differently to different psychiatric medications. Well-done research studies seem to indicate that marijuana would help certain people, while it may not help others. But how to determine which group you fall into remains an exercise for future research.
It may be a few more years before we have a more concrete understanding of the benefits and drawbacks of medical marijuana for mental disorders. Until then, you could try it if you feel comfortable doing so, but as always, you should consult your medical or mental health professional before trying any treatment.