How Do Marijuana Strains And Doses Affect Depression And Anxiety? A New Study Looks For Answers

David DiSalvo,

AFP PHOTO / Robyn Beck / Getty Images

Can marijuana improve symptoms of depression, stress and anxiety, or does it make them worse? As the legalization movement continues pushing forward, that topic is becoming one of the more hotly debated among many, and researchers are trying to find answers. A new study conducted by scientists from Washington State University used a novel approach to address the topic with data from thousands of medical marijuana users, and the results are worth unpacking.

The study used data from the Strainprint app that lets medical marijuana users rate their physical or mental symptoms before and after smoking. Before using, they enter the name of the strain and rate the severity of their symptoms (in this case symptoms of depression, stress and anxiety) and then 20 minutes later they enter how many puffs they took and a new symptom rating.

Using an app like Strainprint to gather study data has a few big limitations (we’ll discuss those in a minute), but one advantage is that the app produced about 12,000 anonymous entries, a solid chunk of data with instructive associations between doses and effects. The data set also allowed researchers to break out effects linked to higher or lower percentages of the two main psychoactive compounds in marijuana: tetrahydrocannabinol (THC) and cannabidiol (CBD). THC is mainly responsible for getting users high, while CBD has been credited in previous studies with a variety of possible benefits.


The results in the latest study suggest that most users experienced positive effects, at least initially. The majority reported a before-and-after decrease in symptom severity for depression, stress and anxiety and not much worsening of symptoms in the short term. A small percentage reported experiencing no change in symptoms.

Here are the breakouts for all of the app sessions tracked in the study ("reduced" means the symptoms improved, "increased" means they got worse):
Depression: Symptom ratings were reduced in 89.3% of the sessions, increased in 3.2%, no change in 7.5%.
Anxiety: Symptom ratings were reduced in 93.5% of the sessions, increased in 2.1%, no change in 4.4%.
Stress: Symptom ratings were reduced in 93.3% of the sessions, increased in 2.7%, no change in 4%.
Both women and men reported an overall reduction in symptoms, but women reported a greater reduction in anxiety symptoms.

An analysis of the strains the app users reported smoking showed a few different outcomes depending on the percentages of THC and CBD. For depression, strains higher in CBD and lower in THC produced the largest reduction in symptoms. For anxiety, CBD and THC percentages seemed to make little difference in the results. For stress, users reported significant symptom reduction when using strains high in both CBD and THC.

The dosage analysis showed that depression symptoms decreased with high CBD strains after just one puff (and more puffs didn’t decrease symptoms beyond that point). For anxiety, symptoms decreased after two puffs of any strain regardless of CBD and THC content (symptoms didn’t decrease further after two puffs), and for stress the largest symptom reduction came after 10 or more puffs of strains high in THC and CBD.

When the researchers examined changes in symptoms experienced over time, they found little change for anxiety and stress, but a significant increase in depression symptoms. That outcome lines up with previous studies showing similar results, indicating an initial, and fleeting, masking of symptoms. Quoting from the study: “This is consistent with recent evidence indicating that using cannabis to cope with distress is associated with more cannabis-related problems and increased symptoms of depression.”

Now for the study limitations, and there are a couple biggies. First, the Strainprint app relies on medical marijuana users to self-report what strains they are smoking, the dose, and how they perceive the effects. Since there’s no good way of strictly monitoring self-reported information, a generous margin of error is baked into these results. We also don’t have a control group to compare results against, so we can’t know how much users were influenced by the placebo effect. The researchers addressed this limitation, among others: “As such, it is possible – and likely – that at least some of the detected effects are driven by expectations individuals have about the efficacy of cannabis for treating states of negative affect.”

The study also wasn’t able to control for the exact percentages of compounds in the strains, although the researchers report that “the majority of the data on THC and CBD levels were obtained from licensed producers who are held to strict testing standards by Health Canada.”

These limitations position this study as a starting point for going deeper with more rigorous, controlled research. The results don’t provide reliable guidelines for using cannabis to treat depression, anxiety or stress, but they can help inform the design of future studies.

A final upside worth mentioning is that the study pulled data from people using medical marijuana as they really use it, not in tightly controlled, artificial environments.

"Existing research on the effects of cannabis on depression, anxiety and stress are very rare and have almost exclusively been done with orally administered THC pills in a laboratory," said lead study author Carrie Cuttler, clinical assistant professor of psychology at Washington State Univeristy.

"We looked at actual inhaled cannabis by medical marijuana patients who were using it in the comfort of their own homes as opposed to a laboratory."

That sort of data isn't easy to come by, and there are trade-offs for using it, as this study shows.