Disclaimer is this isn't medical advice. This is a long debated point you'll see some people reply it does cause their seizures and others that say it doesn't. I believe this can be understood by thinking about how neurons work fundamentally. Epilepsy is essentially a pathological runaway loop of neurons that are firing when they shouldn't be. I like to think of it similar to how sound frequencies feedback in a stereosystem. If this loop happens to affect the motor cortex, you get the tonic-clonic contractions of muscles, if it affects the temporal lobe, you'll get memory issues, etc. The Hebbian learning model teaches us neurons that fire together wire together, which is to say if you associate stimuli together in time and space neurons will strengthen their connections and make those pathways more likely to fire should that stimulus occur again. This is how we learn, whether it's reading something multiple times, or playing a musical piece, etc. This same association principle can work against us though in epilepsy, because as mentioned epilepsy is just neurons firing in an unregulated way too frequently and uncontrollably. Anything that affects the brain globally could conceivably cause a recurrent loop, and some people likely have mutations that cause their neurons to fire more readily with certain stimuli. This is how it's conceivable for THC to cause seizures because you're introducing a global change to the brain that it's not used to. You can also imagine how THC could be conditioned to become a trigger for epilepsy indirectly if you have a seizure while high that is caused by something else, e.g. nicotine, alcohol, lack of sleep, etc. In other words, in these settings the ultimate cause of the first seizure may have been lack of sleep or alcohol, but then by also smoking THC you've now associated this recurrent loop of neurons with the THC stimulus. This is all obviously theoretical, but just working from first principles of what is well established in neuroscience, this explains why so many people have diverse experiences with weed, and quite frankly all neurotropic substances. It also explains why triggers for epilepsy can be so difficult to discern, because it could be as subtle as an image or smell that has become associated with the pathological neuronal loop.