The polarizing question "Does marijuana cause depression?" is a complex one to answer. Smaller observational studies are beginning to address the issue.

Whenever the issue of substance abuse and depression comes up, people often wonder about the role of marijuana. With an ever-increasing number of states legalizing recreational use of marijuana, you may have heard that it can be used to help treat depression. At the same time, experts in addiction often warn that one of the symptoms of marijuana abuse is depression. So, which is it? Does marijuana cause depression—or can marijuana help depression?

The answer is not straightforward. That’s because marijuana affects moods in complex and sometimes unpredictable ways. It can also vary depending on how much is used and how often. Researchers at Colorado State University conducted a detailed survey of 178 marijuana users in their state who were aged 18 to 22. They found that casual users of marijuana had more symptoms of depression than either chronic regular users or nonusers.

The study, led by professor Lucy Troup, a cognitive neuroscientist at CSU, focused on the residual effects of marijuana over time, observing how participants assessed their levels of depression and anxiety. According to results, marijuana appeared to be counterproductive to aiding in the depression and anxiety treatments of individuals. Many of the participants claiming to use marijuana to treat depression or anxiety were found to have misconceptions of how helpful it actually is.

The researchers pointed out, however, that their analysis “does not say that cannabis causes depression or anxiety, nor that it cures it,” according to CSU’s The Source. But it underscores the need for further study around how the brain is affected by the drug, in light of legalization, and by some accounts, more widespread use in Colorado since legalization.”

Evidence for Marijuana Helping Depression

There is some evidence that marijuana can be effectively used to help manage problems that can make people depressed. These include helping to control pain, anxiety, spasticity from movement disorders, and nausea or vomiting. Obviously, if you have any of these problems and they’re getting you down, using marijuana to help relieve them could help lift your mood. But keep in mind that marijuana is less well-studied for these conditions than many other available medications.

Evidence that marijuana directly helps depression is less clear. Research in this area is mainly in its early stages. One preliminary study from the University of Buffalo showed in animals that chronic stress reduces the production of endocannabinoids in the brain. When similar chemicals known as cannabinoids were given to the stressed-out animals, these levels were restored.

Marijuana contains many cannabinoid compounds, so it is possible that stressed-out humans might feel better with marijuana, but experts are a long, long way from being able to confirm its effects.

If you’re depressed, talk with your doctor about whether trying marijuana (if it’s legal in your state) might be right for you. But don’t self-medicate without a doctor’s input, experts advise.

Does Marijuana Cause Depression? Evidence Provides Answer

Some studies have shown that people who smoke marijuana are more likely to be diagnosed with depression. These studies do not make it clear whether the depression is caused by using marijuana, however. It is also possible that people with symptoms of depression are drawn to marijuana because they feel it gives them relief from depression or relief from other conditions ( such as chronic pain) that may contribute to their depression.

The results from a recent Australian study, however, may seem alarming to some. Researchers followed about 1,600 adolescents aged 14 to 15 for seven years. Those who used marijuana regularly were significantly more likely to develop depression. In fact, those who used it daily were five times more likely to develop depression or anxiety later in life. But the opposite was not true. That is, those with depression beforehand were not more likely to use marijuana.

While the Australian study is by no means definitive, its results do suggest that marijuana could increase the risk of developing depression, at least in teens. This is particularly worrisome given other evidence that teens who commit suicide are more likely to be marijuana users.

Marijuana and Mental Health

Marijuana can likely trigger other mental health problems in vulnerable people. For example, it has been shown to trigger episodes of psychosis or dissociation, both of which are unpleasant mental states that disconnect people from reality.

Long-term use of marijuana also has been linked to an overall reduction in motivation, which, while not the same as depression, can appear similar in terms of symptoms. As a result, anyone with mental health problems or at risk for mental health problems should be very cautious about trying marijuana.

Experts advise young people—whose brains are still developing—to stay away from marijuana altogether until more findings and data on its safety are available. For now, it’s too risky.

Keep in mind, too, that marijuana may interact in unpredictable ways with medication that’s been prescribed for depression or other conditions. That’s another reason to clear its use with your doctor.