A new retrospective study from Johns Hopkins finds that adding the ketogenic diet to an existing CBD regimen may provide meaningful seizure reduction in patients whose epilepsy has not responded to standard medications. The sequencing appears to matter: initiating the ketogenic diet after CBD treatment is already underway produced better outcomes than starting either intervention in the other order.
Table of Contents
- When CBD Alone Isn’t Enough: New Data Support Adding the Ketogenic Diet for Treatment-Resistant Epilepsy
When CBD Alone Isn’t Enough: New Data Support Adding the Ketogenic Diet for Treatment-Resistant Epilepsy
A study published today in Epilepsy Research offers a practical clinical signal for patients and families facing pharmacoresistant epilepsy — the roughly one in three people with epilepsy whose seizures continue despite trying two or more appropriately chosen and dosed anti-seizure medications. The Johns Hopkins retrospective chart review of 58 patients found that combining cannabidiol (CBD) with ketogenic diet therapy (KDT) produced seizure reduction comparable to either treatment alone, with a specific advantage when the dietary intervention was layered on top of established CBD treatment.
Pharmacoresistant epilepsy affects approximately 30% of people with epilepsy and represents one of the most clinically challenging conditions seen in cannabis medicine practice. This study speaks directly to the sequencing question that comes up routinely in clinic: when patients are already on CBD, should we add dietary intervention? The answer, based on this new data, appears to be yes, particularly with KDT introduced after CBD stabilization.
What You’ll Learn in This Article
- What this Johns Hopkins study found about combining CBD and the ketogenic diet for treatment-resistant epilepsy
- Why the order of adding these two interventions appears to matter clinically
- How CBD and KDT work through different mechanisms that may explain why they complement each other
- What the study’s limitations mean for how clinicians should interpret these findings
- What patients and families currently managing pharmacoresistant epilepsy should discuss with their care team
TL;DR
- Johns Hopkins researchers reviewed outcomes in 58 patients with pharmacoresistant epilepsy receiving CBD, ketogenic diet therapy, or both
- The combination produced seizure reduction comparable to either treatment alone, with the clearest benefit when KDT was added after CBD had already been initiated
- The study is retrospective and small, which limits its conclusions, but its real-world design reflects actual clinical practice
- For patients who have not achieved adequate seizure control on CBD alone, adding KDT may be a reasonable next step worth discussing with their neurologist
Why This Matters
Pharmacoresistant epilepsy is not a rare edge case. It is the clinical reality for millions of people. Standard anti-seizure medications fail to control seizures in roughly 30 to 40% of epilepsy patients. For this population, the question is not whether to try additional interventions, it is which ones, in what combination, and in what order. Both CBD and the ketogenic diet have independent evidence bases in drug-resistant epilepsy. This study is the first to look at what happens when they are used together, and to examine whether timing of introduction changes the outcome.
Study at a Glance
| Title |
Combining Cannabidiol and Ketogenic Diet Therapy in Pharmacoresistant Epilepsy: A Retrospective Chart Review |
| Journal | Epilepsy Research |
| Published | May 5, 2026 |
| Lead Institution | The Johns Hopkins University School of Medicine |
| Study Design | Retrospective chart review |
| Sample Size | 58 patients with pharmacoresistant epilepsy |
| Interventions | CBD alone; ketogenic diet therapy (KDT) alone; CBD plus KDT |
| Key Finding | Combination therapy showed similar overall seizure reduction to either intervention alone; benefit was most pronounced when KDT was added after CBD was established |
| Primary Limitation | Retrospective design, single center, small sample — no randomization or control group |
| Clinical Implication | Supports considering KDT as an additive intervention for patients already receiving CBD who have not achieved adequate seizure control |
Clinical Summary
The study enrolled 58 patients treated at Johns Hopkins with epilepsy that had not responded to at least two appropriate anti-seizure medications. Patients were grouped by treatment: those on CBD alone, those on KDT alone, and those who received both interventions. Researchers compared seizure frequency before and after treatment in each group and also looked at whether it mattered whether CBD or KDT was started first in the combination group.
Across the groups, seizure reduction was broadly similar between the three treatment approaches. The finding that stood out was a sequencing effect: patients who began the ketogenic diet after their CBD regimen was already underway showed better outcomes than those who received KDT first and then added CBD. This suggests the two therapies may not simply be interchangeable add-ons, but may interact in ways that are sensitive to the order in which they are introduced. The researchers concluded the combination warrants consideration as an additive strategy, particularly when KDT is layered onto an existing CBD foundation.
Two Different Mechanisms, One Common Target
Part of why this combination is scientifically plausible is that CBD and the ketogenic diet reach the brain through entirely different biological routes. CBD interacts with the endocannabinoid system, modulating CB1 and CB2 receptors, affecting TRPV1 ion channels, and reducing neuronal excitability through several overlapping pathways that are still being characterized. It does not work the way classic anti-seizure medications work, which is precisely why it sometimes helps patients who have failed those medications.
The ketogenic diet reduces seizures through metabolic mechanisms. By shifting the brain’s primary fuel source from glucose to ketones, it alters the energy environment in which neurons operate, reduces glutamate-driven excitatory signaling, and appears to enhance GABAergic inhibition. These are not the same molecular levers CBD pulls. The question the Hopkins team was essentially asking is: does engaging two distinct anti-seizure mechanisms at the same time produce something better than either one alone? The answer, in this small but real-world dataset, is: comparably effective overall, and potentially better when sequenced correctly.
Why the Order of Implementation May Matter
The sequencing signal in this study is worth dwelling on because it has immediate clinical relevance. Many families come to cannabis medicine already managing a ketogenic diet, particularly in pediatric epilepsy where KDT has a longer clinical track record. Others are on CBD first and asking whether dietary changes might help further. This study’s suggestion that CBD-first, then KDT may be a more favorable sequence gives clinicians a specific framework to discuss with patients and families considering combination therapy.
It is not yet clear why sequencing matters. One hypothesis is that CBD may help stabilize seizure activity enough to allow the metabolic transition to ketosis to take hold without destabilizing the patient. The ketogenic diet introduces significant physiological changes, including shifts in gut microbiome, mitochondrial function, and neurotransmitter availability. Beginning that transition in a patient whose seizures are already partially managed by CBD may allow a smoother neurological adaptation. This is speculative, but it is a testable hypothesis and one that prospective research could address.
What Kind of Evidence Is This, and What Does It Mean in Practice
Retrospective chart reviews have real limitations. There is no randomization, no control group, and significant potential for selection bias. Patients who received both CBD and KDT may differ in important ways from those who received either alone, and the study cannot fully account for those differences. The sample size of 58 is small by the standards of modern clinical research, and findings from a single center at Johns Hopkins may not generalize to other clinical settings or patient populations.
At the same time, retrospective studies in rare or difficult-to-treat conditions have value precisely because they reflect what actually happens in practice. Randomized controlled trials in pharmacoresistant epilepsy are logistically demanding and can take years to complete. Real-world chart review data from an experienced epilepsy center at a major academic institution captures a kind of clinical truth that idealized trial conditions sometimes cannot. The Hopkins team is transparent about these limitations in the paper, which adds credibility to their conclusions. This is not practice-changing evidence; it is practice-informing evidence, and that distinction matters.
What Patients and Families Should Know
If you or someone you care for has epilepsy that has not responded to standard medications, and you are already using CBD or considering it, this study is worth bringing to your neurologist. It does not mean the ketogenic diet is right for everyone, or that CBD is the first step for every patient. KDT is nutritionally demanding and requires close medical supervision, particularly in children. CBD, meanwhile, carries its own interaction profile, especially with other anti-seizure medications.
What this study adds is a signal: the conversation about combining these two approaches is one the evidence now supports having. For families in Massachusetts and across New England who are already navigating cannabis medicine with us at CED Clinic, this is the kind of real-world clinical data that informs how we think about sequencing and layering interventions, not as a substitute for individual clinical judgment, but as one more input into it.
Further Reading at CED Clinic
For a broader review of the evidence behind CBD in treatment-resistant epilepsy, including safety data and adverse event profiles, see our 2025 systematic review summary: CBD Probably Reduces Seizures in Refractory Epilepsy, But Raises Risk of Serious Adverse Events. For a deeper look at how CBD works in the brain at the mechanistic level, our article on the proposed mechanisms of CBD in epilepsy walks through the relevant biology. And for an overview of the full cannabis and epilepsy evidence base, Medical Cannabis and Epilepsy: The Evidence provides the clinical context.
Pharmacoresistant epilepsy is one of the most humbling conditions I encounter in cannabis medicine practice. These are patients and families who have already tried and failed multiple pharmaceutical options. They are not coming to us looking for a cure. They are looking for reduction, for fewer bad days, for a little more quality of life. When a family asks me whether they should try CBD, or the ketogenic diet, or both, the honest answer has always been: we think both can help, and we think the combination makes biological sense, but we did not have much direct data on the combination itself. We do now.
What strikes me most about this Hopkins study is not the seizure reduction numbers, which are meaningful but modest. It is the sequencing finding. The idea that CBD first, KDT second may outperform the reverse is something I would not have predicted with confidence before this data. It suggests that how we build a treatment plan, the order in which we introduce interventions, may matter as much as which interventions we choose. That is a principle I apply across cannabis medicine broadly, and it is good to see it showing up in the epilepsy literature with some empirical weight behind it. This study is small and retrospective, and I would not revise clinical practice guidelines based on it alone. But it moves the conversation forward in a meaningful way, and that is worth paying attention to.
For families working through this at CED Clinic, my message is consistent: CBD and the ketogenic diet are not competitors, and they are not mutually exclusive. If CBD is your starting point and you are not where you want to be with seizure control, the data now give us a reason to talk seriously about adding KDT. Bring this study to your neurologist and have that conversation. That is exactly the kind of collaborative, informed discussion that leads to better outcomes.
Clinical Perspective: How This Fits the Broader Evidence
The case for CBD in treatment-resistant epilepsy is well-established. FDA approval of Epidiolex, the pharmaceutical-grade CBD formulation, for Dravet syndrome, Lennox-Gastaut syndrome, and tuberous sclerosis complex reflects a genuine and replicated evidence base. The ketogenic diet’s role in pediatric epilepsy has decades of clinical backing, with response rates of 50% or better in appropriately selected patients. What the field has lacked is clear guidance on combination use and, specifically, on sequencing.
This Hopkins study begins to fill that gap. It joins a small but growing body of real-world evidence suggesting that multimodal approaches to pharmacoresistant epilepsy, ones that target neuronal excitability through distinct biological pathways simultaneously, may offer advantages that single-modality treatments cannot. As the field moves toward larger prospective studies of this combination, clinicians working in cannabis medicine have a responsibility to stay current and to bring this evidence into their consultations with patients who are running out of conventional options.
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Disclaimer: This article is intended for educational purposes and does not constitute medical advice. Cannabis medicine should be discussed with a qualified clinician familiar with your individual health history.