Ask the Doctors

Dear Doctor: How often do flashing lights cause seizures? Does it happen only in people with epilepsy? I ask because I recently saw a warning about flashing lights in the new "Incredibles 2" movie.

Dear Reader: While the idea that the makers of an animated children's film would issue a health alert to potential viewers sounds like an urban legend, that is indeed what happened with "Incredibles 2," the long-awaited sequel to "The Incredibles" from Disney. Specifically, several sequences -- in which the film's villain uses a strobelike weapon -- can act as triggers for a seizure for some people. The issue emerged the same day the film opened as discussions of the specific scenes spread on social media. Several blog posts written by people susceptible to seizures due to strobing lights also helped move the issue into the mainstream. According to one blogger, whose post on the topic went viral, "After last night, I can say that the movie is unlike anything I have ever seen before, in that the villain's weapon of choice can hurt not only characters on screen, but can also hurt the people in the audience as well. The weapon? Continuous sequences of rapidly flashing/strobing lights."

The condition is known as photosensitive epilepsy. It affects about 3 percent of those living with epilepsy, which is a disorder of the brain in which abnormal electrical activity can lead to a range of different types of seizures. In photosensitive epilepsy, lights that flash at certain intensities, in certain visual patterns, or with contrasting light and dark patterns, can act as triggers for a seizure. According to the Epilepsy Foundation, photosensitive epilepsy tends to be more common among children and adolescents, particularly those with generalized epilepsy and a type known as juvenile myoclonic epilepsy.

But other populations can be adversely affected by strobing lights and patterns as well. These include anyone who is prone to migraine or other headache disorders, people with vertigo, individuals with autism or ADHD, and those living with non-epilepsy seizure disorders. For these populations, the sequences of the film with the flashing lights -- one scene reportedly lasts for more than a minute -- may not cause seizures, but can lead to headache, nausea, balance issues, light sensitivity, loss of bladder control or general physical discomfort.

There is no cure for photosensitive epilepsy, and once a seizure or other physical reaction has started, there is no way to stop it. Therefore, it's to Disney's credit that, as soon as the issue with the strobe lights emerged, the studio sent out an advisory to all theaters showing the film. The theaters then posted prominent signs, and some even had their ticket takers issue verbal warnings regarding the potentially disruptive scenes.

If this sounds a bit familiar, it may be because back in 1997, an episode of a "Pokemon" cartoon that featured similarly strobing lights adversely affected nearly 700 children in Japan. Many of them wound up in hospitals, and the issue of photosensitive epilepsy moved from medical books to the front pages of newspapers.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

More like Ask the Doctors