As cannabis use becomes more common around the world, scientists are trying to better understand how the drug affects mental health.
While some people believe cannabis is relatively harmless, researchers continue finding evidence that heavy or long-term use may increase the risk of emotional and psychological problems in certain people.
One of the biggest concerns is cannabis use disorder, a condition where people lose control over their cannabis use and continue using it even when it causes problems in their lives.
People with cannabis use disorder may struggle to stop using cannabis, experience cravings, develop withdrawal symptoms, or have trouble functioning normally at work, school, or home.
At the same time, depression continues to affect hundreds of millions of people globally. Major depressive disorder is more than occasional sadness. It is a serious mental illness that can affect sleep, energy, concentration, motivation, appetite, and emotional well-being for long periods of time.
Researchers have long noticed that depression and cannabis addiction often appear together. However, experts were uncertain how strong the connection really was and whether one condition may contribute to the other.
Now, a very large study published in the Journal of Psychiatric Research has provided clearer evidence of this relationship. Researchers analyzed data from 55 separate studies involving more than 3 million people.
The scientists discovered that about 31 percent of people with cannabis use disorder also had major depressive disorder. In other words, nearly one-third of people struggling with cannabis addiction were also dealing with serious depression.
The study also found the opposite relationship. About 10 percent of people diagnosed with depression also had cannabis use disorder. Researchers say this suggests the connection between the two conditions may work in both directions.
To perform the research, an international team of scientists searched major scientific databases for studies published in English and Portuguese through 2024. They then used mathematical methods to combine all the information into one large analysis.
One interesting finding was that the connection between depression and cannabis addiction was much stronger in psychiatric treatment settings than in the general population.
Among members of the public, cannabis addiction rates in people with depression were lower. But among patients already receiving psychiatric treatment for depression, more than 28 percent also met the criteria for cannabis use disorder.
This suggests that people with more severe depression or other mental health challenges may face a higher risk of problematic cannabis use.
Researchers also found that depression and cannabis addiction often remain linked over many years. Some people with cannabis use disorder were not currently depressed but had experienced depression earlier in life.
According to the study, about 20 percent of people with cannabis use disorder were depressed during the time they participated in the studies. However, about 35 percent had experienced depression at some point in their lives.
Scientists believe there may be several explanations for this connection. Some people with depression may turn to cannabis in an attempt to feel calmer, sleep better, or escape emotional pain.
However, frequent cannabis use may also worsen mood symptoms in certain individuals. Researchers suspect cannabis may influence brain systems linked to motivation, emotional control, stress response, and sleep.
Cannabis addiction can also create problems that contribute to depression, including financial stress, relationship difficulties, social isolation, and reduced daily functioning.
Another challenge identified in the study is that cannabis withdrawal symptoms can closely resemble depression. When heavy cannabis users stop using the drug, they may experience irritability, anxiety, low mood, sleep problems, and emotional distress.
This overlap can make diagnosis difficult because doctors may not always be able to clearly separate cannabis withdrawal from major depressive disorder.
The researchers also pointed out that most of the available research came from North America. Because cannabis laws and cultural attitudes differ across countries, the results may not fully apply to all populations worldwide.
Even with these limitations, the researchers believe the findings are important enough to support routine screening.
They recommend that healthcare providers treating depression should regularly ask patients about cannabis use. Likewise, doctors and counselors helping people with cannabis addiction should also check for symptoms of depression.
Early identification of both conditions may improve treatment success and prevent mental health problems from becoming more severe.
If you care about mental health, please read studies about how dairy foods may influence depression risk, and 6 foods you can eat to improve mental health.
For more mental health information, please see recent studies about top foods to tame your stress, and Omega-3 fats may help reduce depression.
Source: Journal of Psychiatric Research.
