The Connection Between Depression and Cannabis Use

A new cross-sectional study by American researchers examined cannabis use among adults in the United States aged 20 to 59 from 2005 to 2016, focusing on its relationship with depression.

Cannabis is one of the most widely used psychoactive substances in the United States. Over the past two decades, its use among adults has steadily increased; from 2002 to 2017, past-month cannabis use rose by 98%, and daily or near-daily use increased by 40%. At the same time, perceived risks associated with cannabis have declined, its availability has grown, and U.S. marijuana laws have become more liberal: 34 states allow medical use, and 11 states permit recreational use.

As a result, scientists are increasingly concerned about the potential consequences of cannabis use, including cannabis use disorder, car accidents, social problems, and mental health disorders. Of particular concern is the possible negative impact of cannabis on major depressive disorder (MDD), which is often associated with cannabis use.

In the U.S., MDD is one of the most common reasons for seeking medical help, affecting over 17 million adults and causing significant impairment. Existing evidence suggests that cannabis may worsen depression symptoms, especially with regular use. Nevertheless, many people believe cannabis is helpful for treating depression. In a national survey of U.S. adults, nearly 50% said they believe cannabis is beneficial for anxiety or depression, and only 15% think it increases the risk of these conditions.

Depression is one of the most frequently reported reasons for cannabis use, with nearly 25% of adults with mood or anxiety disorders reporting cannabis use for self-medication. The belief that cannabis can relieve mood disorder symptoms may be partly due to misleading information in the media and advertising. One of the most common health claims in online ads for recreational cannabis dispensaries is that it treats depression. These messages may be becoming more frequent, while media coverage of marijuana has become more positive and contains less information about risks.

Study Design and Participants

This repeated cross-sectional study used data from 16,216 adults aged 20 to 59 who participated in the National Health and Nutrition Examination Survey (NHANES) in the U.S. from 2005 to 2016. Probable depression was identified using the Patient Health Questionnaire-9 (PHQ-9), a validated and widely used measure of depression in clinical research. Data analysis was conducted from January to February 2020.

The study considered any cannabis use in the past month (i.e., at least once in the last 30 days) and daily or near-daily use (i.e., at least 20 times in the last 30 days).

Key Findings

1. The prevalence of cannabis use among adults increased from 2005 to 2016. In 2005–2006, the prevalence of any past-month cannabis use was 12.2%, and daily or near-daily use was 3.8%. By 2015–2016, these rates had risen to 17.3% and 6.1%, respectively. These trends are consistent with other epidemiological studies. Since cannabis use—especially frequent and intensive use—is linked to negative outcomes (such as car accidents, memory impairment, and psychiatric symptoms), these results highlight the importance of monitoring cannabis use and mitigating its consequences.
2. There was a significant association between past-month cannabis use and depression. A strong link was also found between depression and daily cannabis use. In 2015–2016, over 30% of people with depression reported using cannabis in the past 30 days, and more than 15% reported using it almost daily. Although this study is cross-sectional and cannot determine the direction of the relationship between depression and cannabis use, these findings are concerning, given that both more intensive use and depression are associated with increased risk of cannabis-related harm. People with depression who use cannabis may be at high risk for adverse effects, including worsening depressive symptoms and suicidality. In clinical settings where depression is treated, it may be helpful to discuss cannabis use frequency, reduction strategies, and its impact on depression symptoms with patients.
3. The association between cannabis use and depression strengthened from 2005 to 2016. In 2005–2006, people with depression were 46% more likely to use cannabis and 30% more likely to use it daily compared to those without depression. By 2015–2016, people with depression were 130% more likely to use cannabis and 216% more likely to use it daily than those without depression. These results show that over time, more people with depression are using cannabis. This may be happening as more people with depression use cannabis for self-medication, potentially influenced by media and advertising portraying cannabis as beneficial for health.

What Can We Conclude?

Despite the many potential benefits of cannabis, it should not be relied upon as the sole treatment for serious conditions like depression. Marijuana remains a controversial plant, and its effects on life and health are only now being actively studied. If you have depression, cannabis is not the medicine to use if you want to be healthy. Rely on evidence-based medicine, qualified healthcare professionals, and remember: too much of anything can be harmful!