Is Cannabis Good or Bad for Depression?

“I’ve suffered from bipolar depression since my teens, but I was only formally diagnosed in my 40s,” says Kelly, a 50 year-old pensioner from Edmonton, Alberta, who requested that we not share her last name. “I suffered in private for years.”

Kelly has been using cannabis to self-treat her depression since her teens, and has used it every day since quitting alcohol in 1998. Kelly says consuming cannabis reduces the physical pain associated with depression. “That’s the big part for me. It gives me energy and I can get going,” she explains.

What the research says

Many people like Kelly credit cannabis with helping them cope with symptoms of depression. Anecdotal evidence for the herb’s ability to help abounds, but when it comes to studies and hard evidence, it’s hard to get the whole story.

That’s because human studies on cannabis and depression are observational and not experimental, meaning researchers can’t decide who takes cannabis and who doesn’t. They can only observe people who choose to use and people who don’t, and compare the results. But this study design runs into the age-old problem of correlation vs. causation.

For example, a 2003 review found that cannabis use was actually associated with increased depression in humans. However, since the studies were observational, it’s impossible to tell if the cannabis was causing depression or if people with depression were simply more likely to use cannabis to self-treat.

Recent studies on animals may also help shed some light on the matter. Experiments on animals — which are designed to prove a causal role — have shown that both the cannabinoids THC and CBD have antidepressant effects. THC is the chemical responsible for the cannabis high, while CBD has more subtle, non-intoxicating effects.

A 2014 review of animal studies concluded that CBD showed antidepressant effects. More recently, a 2016 study on a mouse model of depression showed that CBD seemed to have fast-acting antidepressant effects, particularly on symptoms of anhedonia (loss of pleasure).

A 2007 study found that a synthetic cannabinoid mimicking the effects of THC had a strong antidepressant-like effect in rats, and another 2012 study reported antidepressant effects of THC.

These results can help explain why many people find relief from depression in cannabis.

Strain types

Kelly finds certain strains work better for her symptoms than others. “I [prefer to] smoke sativas or hybrid strains. I find indica makes me tired,” she explains.

Although the terms ‘indica’ and ‘sativa’ are scientifically contentious, they have become shorthand for different effects. So-called sativa strains are described as euphoric and energetic, with a “head high”, while so-called indicas are described as more sedative, with a “body buzz”.

Many scientists believe that these differences are not due to genetic variations – as was previously believed – but due to differences in terpene composition. The terpene myrcene, in particular, is believed to be responsible for “flipping” the energetic effects of THC into more of a couch-lock effect. Thus, so-called indica strains, associated with a sedative, body buzz or “couch lock” experience, may actually be high-myrcene strains.

Regardless, both strains we call sativa and strains we call indica may be helpful for depression. Energetic, euphoric sativa strains may help with motivation, anhedonia, and fatigue symptoms. Relaxing, sleepy indica strains may help with restlessness, stress, and insomnia. Each may play a role in a person’s individual treatment plan.

Cannabis for depression in older adults

Now that Kelly is getting older, she has found cannabis to be “even more helpful.” “I’ve developed arthritis [in recent years] and it’s great for the pain,” she says.

Kelly also finds that cannabis mixes well with her other prescriptions, and even helps her deal with side effects.

“Since [being] diagnosed, I’m now on a combination of medications. I take a mood stabilizer, three antidepressants and approximately three grams of weed per day. [It] took four years with my psychiatrist to get the right combination but weed was always the constant,” she explains.

“The weed helps [with the] nausea and other side-effects from my prescribed medications. It was the only thing that could relax me and help me sleep. I’ve been on this combination for five years now and it seems to be working well. I haven’t had a manic episode or a panic attack in years.”

Older adults tend to have higher rates of depression than their younger counterparts. They’re also more likely to take other medications which may interact with their antidepressants, and may experience a number of side-effects as a result. If cannabis can address some of these issues, it may be a helpful adjunct to traditional therapies for older adults in particular.

What the experts say

Natural Care nurse practitioner Lynn Haslam says that treating depression can be challenging.

“Many patients may be unsure of the feelings that they are experiencing. They may question whether they [really] have depression, or if their feelings are normal. Because of this, some patients are hesitant to ask for help. In addition to this, many patients experience side effects from conventional medications.”

Haslam emphasized the lack of human research on cannabis and depression, but has a theory of her own:

“There [are not very many] human studies that look at cannabis for treatment of depression. We do know that chronic stress may suppress the production of endocannabinoids, which can lead to depression symptoms. Theoretically, an introduction of cannabis into the system may help to restore normal levels of the body’s natural endocannabinoids, and ease symptoms of depression.”

If someone uses cannabis as part of their depression treatment plan, it’s extremely important important to inform their healthcare provider, Haslam says, adding that cannabis is often best used as an adjunct to other therapies.

“I think careful and slow titration of cannabis in someone with depression may be a [beneficial] adjunct to conventional treatments,” she says.

The takeaway

Many people report that cannabis is a useful part of their depression treatment plan. For some, it may help with the side-effects of other pharmaceuticals, or it may treat a number of conditions at once. While human studies are challenging to design and control, animal studies have shown promising results for both THC and CBD. Cannabis is often best used as an add-on to other treatments. If you decide to use cannabis for depression, it’s important to always let your healthcare provider know.