Epilepsy covers a very wide range of 'conditions' from short (split-second) unconsciousness - without fanting,
irrational actions*, to generalized tonic-clonic seizures as most people associate with the disease.
In some cases - about 5 percent of those with epilepsy - flashing lights (or patterns with contrasting colours) can cause these seizures.
*These irrational actions can in some cases imitate insanity, but the person is unaware of his/her actions.