Does Marijuana Really Increase the Risk of Depression?

Marijuana comes from the cannabis plant and is one of the most commonly abused drugs in the United States.

Recently, numerous states have legalized the use of marijuana for medicinal purposes, and some states have legalized its use for recreational purposes; however, it remains classified as a Schedule I drug by the United States Drug Enforcement Administration.

Individuals who abuse any type of drug, including cannabis products, are at a greater risk to also be diagnosed with other psychological disorders, such as major depressive disorder. There is a large body of research that has attempted to investigate the nature of the relationship between major depressive disorder and the use of cannabis products.

Some of the Research Findings

doctor going over research findings about risk of depression from marijuana with patient

There are literally hundreds of research studies attempting to ascertain the relationship of cannabis use and having a diagnosis of major depressive disorder or some other psychological disorder. A few of the major studies in the research literature and their findings are described in this section.

In an article published in the journal Addiction, participants in Australia who completed the National Survey of Mental Health and Well-Being were utilized to determine if there was a relationship between cannabis use and depression. The researchers found a positive relationship between a diagnosis of depression and cannabis use, such that the relationship was more robust as individuals had histories of heavier cannabis use or problematic cannabis abuse. However, when the researchers controlled for the use of other drugs, such as tobacco and alcohol, the relationship between cannabis use and depression was no longer significant. Moreover, there was no evidence to support the notion that people with depression self-medicate their symptoms with use of cannabis. The researchers surmised that there was no direct causal relationship between the use of cannabis products and a diagnosis of major depressive disorder. However, the researchers hypothesized that the relationship between cannabis use and depression may be an indirect one, such that individuals who use cannabis and have significant issues with depression often have what is known as an avoidant coping style, which consists of individuals not attempting to directly address their emotional problems. Instead, these individuals will use drugs to cope with emotional distress. The authors hypothesized that the relationship between cannabis use and depression might be accounted for by individuals who have this type of coping style.

A research article published in the American Journal of Drug and Alcohol Abuse utilized data from the National Comorbidity Survey from the United States to assess the prevalence of the different mental health disorders in individuals with cannabis use disorders. The findings indicated that the vast majority of individuals with cannabis use disorders in the study also had some diagnosis of a mental health disorder in their lifetime compared to only about half of the control group that did not have issues with cannabis abuse. The individuals with cannabis use disorders were over two times more likely to have issues with clinical depression than those who did not abuse cannabis. However, the results of these findings were not significantly different from findings that occur in individuals with tobacco use disorders and their rates of diagnoses for depression. Thus, the overall relationship between cannabis and depression does not suggest a specific causal relationship but a more general type of relationship between depression and numerous drugs of abuse.

A more recent study reported in the open access journal PeerJ in 2016 investigated the relationship between depression and cannabis use in Colorado after cannabis products had been legalized. The researchers investigated the relationships of anxiety, depression, and cannabis use in college students. Three groups were compared:

  • A control group that reported never using cannabis products
  • A casual user group
  • A chronic cannabis user group

All three groups completed two psychometric instruments, the Center for Epidemiological Studies Depression Scale and the State – Trait Anxiety Inventory. The findings indicated that there was a relationship between casual cannabis use and higher scores on the depression scale, but there was no relationship between cannabis use and scores on the anxiety scale. The chronic cannabis users and the control group did not have significantly higher scores on the depression scale from one another (contrary to the findings in one of the above studies). These relationships did not suggest a causal connection, and the researchers admit that there are numerous flaws in the data. The most glaring conclusion from the study was that more research needs to be performed in order to understand the relationship between cannabis use and mood disorders.

Interestingly, numerous professional organizations like Mayo Clinic and the National Institute on Drug Abuse (NIDA) recognize that in many studies there is a relationship between significant depressive symptoms and the use of drugs like cannabis products; however, research has not yet determined the nature of this relationship. In addition, NIDA reports that there is a relationship between the use of cannabis products and other types of psychiatric conditions, such as psychosis, but again, no conclusions regarding the use of cannabis causing individuals to develop specific types of psychological disorders can be reliably stated based on the volumes of research available.

What Is Known?

What it boils down to is that individuals who are prone to developing issues with substance abuse are also prone to developing other types of psychological disorders, including depressive disorders, anxiety disorders, bipolar disorder, etc. This relationship is not a direct causal one, such that it can be definitively stated that using cannabis products leads to the development of some other psychological disorder or that the development of some psychological disorder results in one using cannabis more often. As it turns out, in some cases, individuals may have had pre-existing psychiatric issues and began using drugs like cannabis products, and in other cases, individuals started out using drugs and/or alcohol and later began to display symptoms consistent with different types of mental health disorders. The fact of the matter is that numerous risk factors interact in ways that are not fully understood that result in an individual being more prone to develop any type of potential mental health disorder. These risk factors include:

  • Genetics: Numerous research studies have linked specific genetic factors to increased risks for the development of different types of psychological issues. However, the research is often inconsistent; difficulties replicating research findings regarding genetic influences on behavior are common. In addition, the studies often have serious methodological issues, and there are no genetic markers that can be used to diagnose the majority of mental disorders listed in the Diagnostic and Statistical Manual of Mental Disorders – Fifth Edition. Individuals who have family members with a history of being diagnosed with these disorders are at an increased risk to develop some type of psychological disorder themselves. While the observation that having a family history of some disorder is most often associated with genetic factors, having family history of substance abuse can also easily be linked to learning this behavior as well.
  • Environmental experiences: Certain types of environmental experiences are linked to an increased risk of developing both depression and any type of substance use disorder. These environmental experiences include but are not limited to:
  • A history of physical or sexual abuse
  • Being separated from one’s parents as a result of a parent dying or divorce
  • Poor parental supervision
  • Involvement with peers who use drugs or alcohol
  • Growing up in an environment where drug use is considered an acceptable coping strategy
  • Other variables: Certain demographic features appear to increase the risk of developing depression, substance abuse, or both that can include gender, social economic status, cognitive impairment, having certain physical conditions, etc.

Risk factors are conditions or experiences that can increase the probability that one will develop some specific disorder or condition, but their presence or absence does not guarantee that the individual will or will not develop the disorder. Risk factors are also cumulative, such that individuals who have several risk factors are at a greater risk to develop a specific type of disorder/condition.

The relationship between the use of any type of substance, including cannabis, and the development of mental health disorders, such as depression, may be best explained by the notion of common liability, such that individuals who meet the diagnostic criteria for one type of psychiatric disorder are at greater risk to also be diagnosed with any another type of psychiatric disorder. Thus, individuals who would meet the diagnostic criteria for a substance use disorder would be a greater risk to be diagnosed with any other type of psychological disorder and vice versa.

Individuals Who Suffer from Clinical Depression Should Not Abuse Drugs

Unless a person is prescribed a specific medication for the treatment of depression or some other medical condition by a licensed physician, individuals who have issues with depression should not use any type of drugs, including cannabis products, for several reasons.

  • Cannabis interferes with judgment. Individuals under the influence of marijuana or other cannabis products often have their decision-making ability affected. For individuals who already have pre-existing issues with depression, this can lead to issues with impulsive behaviors (e.g., suicidality, accidents, mixing cannabis with potentially dangerous drugs, disruption of personal relationships, ignoring personal responsibilities, etc.). The ramifications of actions while using cannabis products may be quite severe and may fuel depression.
  • The side effects of cannabis use can exacerbate depressive symptoms. The side effects include:
  • Increased feelings of jitteriness or anxiety
  • Suppressed thinking rate
  • Increased risk to develop numerous physical conditions, including issues with one’s respiratory system and cardiovascular system
  • Less physical activity, which can exacerbate issues with depression
  • Neglected personal care, which can exacerbate depressive symptoms
  • The development of tolerance to and withdrawal from cannabis, which can increase one’s level of depression if one cannot habitually use cannabis products
  • Use of cannabis is often a method of avoiding personal issues. The practice of avoiding dealing with one’s difficulties will simply make it more difficult for one to actually cope with these difficulties.

While it is still uncertain that the use of cannabis products causes an individual to develop depression, or that individuals who have pre-existing depression are more likely to use cannabis products, it is best for individuals who have pre-existing issues with depression to avoid use of cannabis and other drugs that are not formally prescribed to them. This can help to ensure that individuals can proactively address their issues with mood through the use of prescribed medications, therapy, support, and other interventions like diet and exercise.

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