Friends are double dosing: Marijuana and Prozac

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,

The mere fact that you’ve asked such a thoughtful question shows that you genuinely care about the well-being of your friends. Regardless of why your friends may be using marijuana, it’s possible that mixing it and Prozac (generic name: fluoxetine) may be having negative effects on their health. To date, there have been a few studies which have revealed that marijuana may inhibit fluoxetine’s efficacy, and the two combined could produce unpleasant and unsafe side effects such as paranoia, fatigue, and mood swings. However, for the most part, there hasn't been extensive research investigating the interactions between the two substances. As such, it’s strongly recommended that your friends speak with their respective medical providers about their individual experiences, so they can learn about any risks they may face.

Although not much is known about how the two substances may influence one another, 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 any antidepressant, it comes with its fair share of side effects, including nervousness, drowsiness, anxiety, restlessness, sleepiness, or insomnia. Fortunately, these side effects usually improve within one to two weeks of use when used as indicated 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 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, and the worse the side effects may be. And sometimes, these symptoms can be even worse when marijuana has been laced with other drugs, such as phencyclidine (PCP), where feelings of paranoia are more likely to occur. So, on its own, marijuana might result in uncomfortable side effects and experiences.

With your friends’ current mental health in mind, it’s worthy to note that marijuana use has been shown to cause some depressive symptoms in people, particularly heavy users. 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. Also, 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 decision to currently mix it with fluoxetine might be exacerbating their symptoms. However, this is just speculation 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. Thus, certain activities including schoolwork, job responsibilities, and driving may become particularly difficult or unsafe when double-dosing.

Now, you might be skeptical about the idea of your friends speaking with their medical providers, depending on the legality of marijuana where they live. While this is an understandable and common concern, rest assured that if they’re in the United States, your friends are typically protected by laws that protect confidentiality between health care providers and patients. Regardless of where your friends live, 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, as it can help prevent various undesirable drug interactions. With this in mind, if your friends are also concerned, it could be beneficial for them 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.

As a friend, you may choose to talk to your friends about what you’ve noticed with their behavior and can provide them with this information and express your concern for their well-being. It might be helpful for your friends to consider how their cognitive abilities are being impacted. If they’re concerned about these changes in behavior, you can also recommend that they speak with a health care provider or mental health professional. They're lucky to have someone as observant and caring as you are looking out for them. For additional information on talking with your friends, consider checking out I'm worried about my friend's escalating drug use in the Go Ask Alice! archives.

Hopefully this helps!

Last updated Sep 29, 2017
Originally published Sep 17, 1999

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