Lennox-Gastaut Syndrome Diagnoses Spiked After FDA Approved CBD — Then Returned to Normal | Research

The takeaway

New LGS diagnoses jumped nearly 60% after CBD was approved for the condition in 2018, suggesting some diagnoses may have been influenced by treatment availability rather than clinical criteria.

Epileptologists, FDA policy analysts, ICD coding researchers, diagnostic accuracy advocates

What the researchers found

Annual LGS incidence rose ~30% from 2018 to 2019 and ~60% from 2017 to 2019, before returning to pre-approval baseline (2020-2023). This temporary spike occurred in temporal proximity to the 2018 FDA approval of CBD (Epidiolex) for LGS-associated seizures.

Why it matters

If new treatments drive diagnoses rather than the other way around, it undermines both clinical accuracy and research integrity. This pattern suggests some patients may have been labeled with LGS specifically to access CBD treatment.

The numbers in context

Incidence rate: ~30% increase 2018-2019, ~60% increase 2017-2019. Returned to baseline 2020-2023. Temporal correlation with June 2018 FDA approval of Epidiolex for LGS.

How the study worked

Retrospective analysis computing annual new LGS diagnoses in the US from 2017-2023 using a large population-based electronic health record database.

What this study cannot tell us

Administrative data with ICD codes cannot confirm diagnostic accuracy. Cannot prove causation between CBD approval and diagnosis increase. Multiple factors may have contributed. COVID-19 may have affected 2020-2021 diagnostic patterns. Insurance coding practices may have changed independently.

How to read the evidence

Large population-based database provides reliable trend data, but administrative records cannot distinguish genuine incidence changes from coding practice changes.

When this study was published

Published 2026 analyzing 2017-2023 EHR data following 2018 Epidiolex FDA approval.

The bigger picture

This is a cautionary tale about how treatment availability can distort diagnostic practices — relevant beyond just epilepsy, as new cannabis-based treatments for other conditions could create similar diagnostic inflation if criteria aren't strictly maintained.

Questions still open

Were the excess diagnoses actual LGS, diagnostic code updates, or misdiagnoses? Did patients who received expanded LGS diagnoses benefit from CBD treatment? Should approval of new treatments trigger enhanced diagnostic auditing?

Common questions

Did CBD approval change how often Lennox-Gastaut syndrome was diagnosed?

It appears so — new LGS diagnoses jumped about 60% in the year after CBD was approved for the condition, before returning to normal levels by 2020, suggesting some diagnoses may have been motivated by treatment access.

Were people being misdiagnosed to get CBD?

The study can't prove that, but the temporary spike and return to baseline strongly suggest that at least some of the increase reflected diagnostic practices influenced by treatment availability — including possible code updates and misdiagnosis of other severe epilepsies as LGS.

Read the original research

A temporary spike: Investigating Lennox-Gastaut syndrome incidence in the US following FDA approval of cannabidiol.

Epileptic disorders : international epilepsy journal with videotape

View on PubMed ↗Publisher’s paper ↗

Citation

Marcinski Nascimento, Kaley J; Li, Yifan; Lin, Binx Y; Dixon-Salazar, Tracy; Perry, M Scott; Xu, Kevin Young; Nascimento, Fábio A. (2026). A temporary spike: Investigating Lennox-Gastaut syndrome incidence in the US following FDA approval of cannabidiol.. Epileptic disorders : international epilepsy journal with videotape. https://doi.org/10.1002/epd2.70168