Can Tetrahydrocannabinol (THC) interact with Selective Serotonin Reuptake Inhibitor (SSRI) medications?

From the Guidelines

Yes, THC can potentially interfere with SSRI medications, and this interaction may increase the risk of serotonin syndrome, a potentially serious condition. The most recent and highest quality study, 1, published in 2024, highlights the potential for drug-drug interactions between cannabis and/or cannabinoids with systemic medications, including SSRIs. Although the study focuses on the use of cannabis in adults with cancer, its findings on the pharmacokinetics and pharmacodynamics of THC and CBD are relevant to the potential interaction with SSRIs.

Key Considerations

• THC and SSRIs are metabolized by the same liver enzymes (cytochrome P450), which can lead to higher blood levels of either substance.
• Both substances affect serotonin and other neurotransmitters in the brain, and their combined effects may be unpredictable.
• The risk of serotonin syndrome, characterized by agitation, confusion, rapid heart rate, high blood pressure, dilated pupils, muscle rigidity, and in severe cases, seizures or loss of consciousness, is a concern when combining THC and SSRIs.

Recommendations

• If you're taking SSRIs and considering using cannabis products containing THC, it's essential to consult with your healthcare provider first.
• Your healthcare provider may need to monitor you more closely or adjust your medication dosage to minimize the risk of adverse interactions.
• Never stop taking prescribed SSRIs suddenly to use cannabis, as this can lead to withdrawal symptoms and worsening of the condition being treated.

Additional Information

• A study published in 2021, 1, notes that the risk of serotonin syndrome with combining triptans and SSRIs or SNRIs is low, but it's still important to exercise caution when using these medications together.
• Another study published in 2023, 1, highlights the potential for drug-drug interactions between ozanimod and serotonergic/adrenergic drugs, including SSRIs, which further emphasizes the need for careful consideration when combining these medications.

From the Research

THC and SSRI Interactions

• THC can potentially interfere with SSRI medications, as it may alter serotonergic transmission and modulate SSRI response 2
• The combination of THC and SSRIs may increase the risk of adverse events, such as cough, diarrhea, dizziness, and fatigue 2
• Cannabinoids, including THC, can inhibit cytochrome activity, which may affect the metabolism of SSRIs and increase their concentrations in the body 2

Serotonin Syndrome Risk

• The use of SSRIs and other serotonergic drugs, including THC, may increase the risk of serotonin syndrome, a potentially life-threatening condition 3
• Serotonin syndrome is characterized by increased serotonergic activity, which can cause symptoms such as neuromuscular abnormalities, autonomic hyperactivity, and mental state changes 3
• The risk of serotonin syndrome is higher when multiple serotonergic drugs are used concurrently, and clinicians should be aware of this potential interaction when prescribing SSRIs to patients using THC 3

Clinical Considerations

• Clinicians should discuss THC use with patients prescribed SSRIs and monitor for potential interactions and adverse events 2
• The decision to continue or discontinue SSRI treatment should be made on a case-by-case basis, taking into account the patient's individual risk-benefit profile and potential interactions with THC 4
• Patients using SSRIs and THC should be closely monitored for signs of serotonin syndrome and other adverse events, and clinicians should be prepared to adjust treatment as needed 3, 2