By Alice || Edited by Go Ask Alice Editorial Team || Last edited Jun 09, 2023
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Cite this Response

Alice! Health Promotion. "Friends are double dosing: Marijuana and Prozac." Go Ask Alice!, Columbia University, 09 Jun. 2023, Accessed 24, May. 2024.

Alice! Health Promotion. (2023, June 09). Friends are double dosing: Marijuana and Prozac. Go Ask Alice!,

Dear Alice,

I have two friends who were recently diagnosed with depression. They were both prescribed Prozac by their respective doctors. Both of them are heavy marijuana users and both failed to mention that to their doctors. One has been on Prozac for two months and the other for six weeks. I have noticed that their behavior has become strange: mood swings, paranoia, oversleeping, fatigue. They continue taking their Prozac (20 mg a day) and continue smoking pot. I am afraid that there might be some negative interaction between the substances, one being an antidepressant and the other a depressant. Can you provide some insight?

— Concerned Friend

Dear Concerned Friend, 

Regardless of why your friends may be using marijuana, it’s possible that mixing it and Prozac (also known by its generic name fluoxetine) may be having negative effects on their health. Research investigating the interactions between the two substances is limited. However, those studies that have been conducted have shown that marijuana may inhibit fluoxetine’s efficacy. When the two are combined they could produce unpleasant and unsafe side effects such as paranoia, fatigue, increased heart rate, and mood swings. It’s strongly recommended that your friends speak with a medical provider about their individual experiences so they can learn about any risks they may face. 

Although the exact interaction between fluoxetine and marijuana is still being looked into, much is known about the effects of each substance on its own. Known for being one of the most common antidepressants on the market, fluoxetine is a selective serotonin reuptake inhibitor (SSRI). As an SSRI, it treats depression by altering the brain’s ability to absorb serotonin—a neurotransmitter that's involved in the regulation of emotions and mood. As with many antidepressants, it comes with its fair share of side effects including nervousness, drowsiness, anxiety, restlessness, sleepiness, and insomnia. Fortunately, these side effects usually improve within one to two weeks of use when used as directed by a health care provider. It may also be helpful to know that it can take between four and five weeks before people start to feel the full effects of the medication. That being said, the side effects of fluoxetine may resemble some of the side effects of marijuana use. 

As a psychoactive drug, marijuana can have varying effects on a person depending on their mood, surroundings, and frequency of use. Based on these factors, it can act as a sedative, hallucinogenic, or a stimulant. Though the majority of users smoke or eat it because of its associated “high” feeling, it can result in a lousy time for others. On its own, it can cause mood swings, fatigue, paranoia, worsened symptoms of schizophrenia, and anxiety. With an increased dosage comes an increased likelihood that marijuana will have a hallucinogenic effect. When marijuana is laced with other drugs, such as phencyclidine (PCP), symptoms can be even worse and include feelings of paranoia. On its own, marijuana has the ability to result in uncomfortable side effects and experiences. 

With your friends’ current mental health in mind, it’s worth noting that marijuana use has been shown to cause some depressive symptoms in people as well, particularly in heavy users—this is considered to be daily or more. While some people with major depressive disorder (MDD) report using marijuana to reduce their symptoms, some studies found that it can create more depressive-like behaviors in those experiencing MDD. Additionally, compared to non-marijuana users, frequent marijuana users report poorer mental health outcomes and lower life satisfaction. As such, it’s possible that your friends’ marijuana use prior to fluoxetine may have influenced or heightened their depressive states, and their current decision to mix it with fluoxetine might be making their symptoms worse. However, this is only a guess and can only be confirmed by a medical provider. 

In addition to altering your friends emotional and physical states, fluoxetine and marijuana can alter their cognitive abilities—especially when combined. On its own, marijuana is known to lessen a person’s ability to concentrate and alter their general perceptions of space and time. Much like marijuana, fluoxetine has been found to affect motor skills, decision-making skills, and perception. This can make certain activities including schoolwork, job responsibilities, and driving particularly difficult or unsafe when double-dosing. 

Medical providers need to know about their patients’ potential illicit, prescription, and over-the-counter drug use; by being informed, they’re able to make safe and appropriate recommendations and avoid suggesting something that may result in an undesirable drug interaction. If you feel comfortable, you might talk with your friends about your concerns, and encourage them to speak to their medical provider about their drug use. If they're worried about getting in trouble or other people finding out about their drug use, note that if they’re in the United States, your friends may be protected by laws that ensure confidentiality between health care providers and patients. Another strategy to consider might be for your friends to monitor their drug usage—whether it be prescription, over the counter, controlled, or illicit—and record any noticeable changes in their moods, behaviors, or physical and cognitive abilities. After taking these notes, they could meet with their medical providers who can potentially shed light on why they are experiencing unpleasant symptoms and seek to mitigate them. 

If your friends decide to make any changes regarding their substance or medication use, they should note that suddenly going off of antidepressants can make depressive symptoms more intense. Therefore, if they want to stop taking fluoxetine, it’s recommended that they speak with a health care professional first so that they can make a plan to taper the medication over time. The good news is that there are alternative forms of treatment if your friends decide that they don’t want to use fluoxetine anymore. Cognitive behavioral therapy (CBT), exercise programs, and a healthy sleep routine have all been associated with reduced depressive symptoms. Keep in mind, though, that how “right” a treatment method is for a person will depend on factors such as how severe their depression is, how long they have had depression, their preferences when it comes to treatment, and whether or not they are impacted by any side effects. 

As a friend, you may choose to talk with your friends about what you’ve noticed with their behavior and can provide them with this information while expressing your concern for their well-being. If you choose to do so, it’s a good idea to talk to them in a private, comfortable place that may help them to be more open to discussion. You could try expressing to them what worries you about their drug use and listen to how they feel about it. It’s possible that they might become defensive or angry, so you may want to ensure that you are calm and patient when you approach the subject. If they’re also concerned about these changes in behavior, you could recommend that they speak with a health care provider or mental health professional—just make sure that you do so in a supportive, non-judgmental way. Your friends are lucky to have someone as observant and caring as you looking out for them. Remember, too, that your own mental health is important and deserves just as much care! 

Wishing you and your friends peace moving forward 

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