In 5 star hotels, bananas are often in a bowl at the check in desk, for their calming affect on travelers. I would be surprised if they typically increased anxiety.
Bananas contain a natural chemical which can make a person happy. This same chemical is actually also found in Prozac. I forgot what the chemical is called, but you can look it up....
Most people with anxiety, even extreme anxiety, seldom have seizures. I doubt the banana had anything to do with it, but in truth, I don't know that for sure. Call your local pharmacist and they can hopefully answer this question for you. But.........if someone you know is having seizures, get them to the ER immediately and let the doctors figure out what is causing them.
Seizures are very serious and time should not be wasted trying to figure out if fruit is the trigger.
Peace
Greenlydia