Generalized seizures can be caused by anything that disrupts the normal functioning of the brain. Sometimes generalized seizures can begin as partial seizures. This may occur when a condition (e.g. head injury, brain tumor) that affects a specific portion of the brain causes increased neuron (nerve cell) activity to spread throughout the brain. Conditions that cause illness throughout the whole body (e.g. severe infections, immune system disorders, low blood-sugar level as a result of diabetes) can cause generalized seizures.

Other common causes of generalized seizures include:

• High fever (102 degrees Fahrenheit or 39 degrees Celsius)
  
• Medication interactions
  
• Drug or alcohol abuse and withdrawal
  
• Metabolic abnormalities

The majority of people who experience a generalized seizure never have another seizure. However, generalized seizures may recur when they are caused by chronic neurological conditions, such as epilepsy. Having more than one idiopathic seizure (a seizure with no known cause) may be an indication of this condition.

People who are taking seizure medications for epilepsy are most likely to have a seizure if they miss a dose of medication. Other triggers for people with epilepsy may include lack of sleep, alcohol use, illness or fever.

Generalized seizures may also be triggered by certain sensory information. A small proportion of people who have epilepsy characterized by generalized seizures are particularly sensitive to light. This is called photosensitivity. Television screens, computer games and strobe lights are common triggers of seizures in these people, although the amount of light stimulation needed to trigger a seizure may vary from person to person. Studies indicate that lights that flash between 5 and 30 times per second are most likely to trigger seizures in people who are photosensitive.