National Alliance on Mental Illness
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Marijuana and Mental Illness

Marijuana is the most commonly used illegal drug in America: approximately one in 10 adult Americans report having used marijuana in the past year. In recent years, laws addressing the use and possession of marijuana have been changing, and many states—including Colorado, California, Massachusetts and others—have passed regulations either legalizing marijuana for medical purposes or decriminalizing the non-medical use of marijuana. While different groups of professionals have had varied responses to the implications of this new legislation, mental health professionals have been largely united in expressing their concerns of the negative impact marijuana has for people with mental illness. Furthermore, the scientific data is clear that regular marijuana abuse is linked with increased risk of legal troubles and jail time, difficulties at school and at work, as well as abuse of alcohol and other drugs.

What happens when a person uses marijuana?

Marijuana causes a person to feel “high,” which can involve peaceful feelings such as being happy, silly, hungry or tired. People with mental illness are more likely to also experience negative emotions such as depressed mood, anxiety—including physical symptoms of shortness of breath and heart palpitations—or even paranoia. These reactions are most likely related to marijuana’s interactions with certain chemicals in the brain, including the neurotransmitter dopamine.

Many people incorrectly believe that marijuana isn’t addictive. While many people who use marijuana do not become addicted to this drug, recent scientific research has shown that a significant percentage of individuals who use marijuana will become physically dependent on the drug. This means that stopping their marijuana abuse will cause these people to experience a withdrawal syndrome. While not a medical emergency—compared with withdrawal from other substances such as alcohol—it can cause symptoms of fatigue, low energy and worsening depression or anxiety.

What is the relationship between marijuana and mental illness?

The overwhelming consensus from mental health professionals is that marijuana is not helpful—and potentially dangerous—for people with mental illness. Using marijuana can directly worsen symptoms of anxiety, depression or schizophrenia through its actions on the brain. People who smoke marijuana are also less likely to actively participate in their treatment—missing more appointments and having more difficulty with medication-adherence—than people who abstain from using this drug.

The relationship between marijuana and psychotic illness, specifically schizophrenia, has been studied for many years and is receiving increasing publicity in the mainstream media. Certainly not all people who smoke marijuana will develop schizophrenia, but people who are at risk of developing this illness—including individuals with close family relatives that have severe mental illness—will be more likely to experience psychosis if they are using marijuana. In this population of individuals, people who regularly smoke marijuana are diagnosed with schizophrenia at a younger age, hospitalized more frequently for their illness and are less likely to experience complete recovery even with high quality treatment. This is particularly concerning, as approximately one-third of people in America with schizophrenia regularly abuse marijuana.

What is the relationship between marijuana and medical illness?

The specifics of “medical marijuana” are largely beyond the scope of this review. However, it should be noted that while marijuana has been shown to be helpful in certain specific medical illnesses—such as severe pain caused by cancer—it is by no means a first-line treatment for these conditions. In fact, the majority of people who use marijuana—even for medical purposes—are at risk of significant side effects. Similar to smoking cigarettes, people who smoke marijuana are at increased risk of developing both chronic lung disease and lung cancer. Marijuana has also been shown to affect the reproductive hormones in the body and can cause significant side effects, such as problems with menstruation in women and gynecomastia (development of breasts) in males. Marijuana has also been linked with other medical problems including dental problems and cardiovascular concerns in older patients.

What treatments are available for people with marijuana abuse and dependency?

Multiple scientific studies have shown that treatment of mental illness is more effective in people who are not actively abusing marijuana. This is not to say that people with mental illness cannot be treated while they are still using marijuana; however, treatment of mental illness is generally more effective once individuals are sober and more able to be actively participate in their treatment.

There is no medication that can cure marijuana abuse. A number of different medications have been studied, but the details of this are largely beyond the scope of this review and have not yielded consistent results. Some people find therapy to be a helpful part of maintaining their sobriety. This can include self-help groups such as Marijuana Anonymous, Alcoholics Anonymous, Narcotics Anonymous or Smart Recovery. Individual therapy can also be useful, and some people will find that cognitive behavioral therapy (CBT) is an important part of their treatment plan. Another form of therapy called “motivational interviewing”—an interactive, patient-centered model of treatment focused on finding inspiration for behavioral change—has been found to be effective in helping people to stop using marijuana. These and other tools can be useful, as a significant majority of people will relapse at some point in their lives, even if they are eventually able to achieve long-lasting sobriety.

Family, friends and others can be most helpful in providing empathic and non-judgmental support of their loved ones. With this support and effective psychiatric treatment, many people with marijuana abuse and mental illness will be able to actively participate in their recovery journey.

Reviewed by Ken Duckworth, M.D., and Jacob L. Freedman, M.D., March 2013