About 1 in 26 people will develop epilepsy during their lifetime, and many more will experience at least one seizure from a temporary trigger. Risk isn’t evenly distributed. Certain age groups, medical histories, and metabolic conditions raise the odds significantly, and some of these factors are preventable or manageable.
Age: Highest Risk at Both Ends of Life
Seizures are most likely to begin during two life stages: early childhood and after age 65. These aren’t the same types of seizures, and the underlying causes differ sharply.
In children, the most common seizure type is the febrile seizure, triggered by fever. Most febrile seizures happen between 6 months and 5 years of age, with the highest risk window between 12 and 18 months. Even a low-grade fever can set one off. The risk of having another febrile seizure goes up if the first one happened before 18 months, if it was triggered by only a mild fever, or if a close family member also had febrile seizures as a child. Febrile seizures are frightening to witness but rarely cause lasting harm, and most children outgrow them entirely.
In older adults, the picture is different. Stroke is the leading identifiable cause of new seizures after 65, responsible for more than half of cases where a cause can be pinpointed. Dementia and other neurodegenerative conditions also raise the risk. As the brain accumulates vascular damage or loses neurons over time, its electrical activity becomes less stable, making seizures more likely even in someone who has never had one before.
Family History and Genetics
Having a first-degree relative (parent, sibling, or child) with epilepsy roughly triples your risk of developing the condition yourself. A large population-based study in Rochester, Minnesota found that the chance of developing epilepsy by age 40 was about 4.7% for people with an affected first-degree relative, compared to 1.3% in the general population. The risk was similar whether the affected relative was a parent, sibling, or offspring.
Some forms of epilepsy are tied to specific genes, though in about half of all epilepsy cases, no clear cause is ever identified. Having a genetic predisposition doesn’t guarantee seizures. It simply lowers the threshold, meaning it may take less of a trigger to set one off.
Traumatic Brain Injury
A serious head injury is one of the strongest known risk factors for developing epilepsy later in life. After a severe traumatic brain injury, 10 to 20% of survivors develop post-traumatic epilepsy. A study tracking severe TBI survivors over time found that 25% had experienced seizures within five years, and 32% within fifteen years. That long timeline matters: seizures can start appearing years or even a decade after the original injury, well after someone assumed they were in the clear.
Milder head injuries carry a lower but still elevated risk. The more severe the injury (longer loss of consciousness, skull fractures, bleeding inside the skull), the higher the chance of seizures developing down the road.
Brain Infections
Infections that cause inflammation in the brain or the membranes surrounding it are a well-established seizure trigger. Meningitis produces seizures in roughly 23 to 29% of cases during the acute phase of illness. Encephalitis, which involves direct inflammation of brain tissue, carries a similar or higher risk. These seizures happen because the infection disrupts normal electrical signaling in the brain, sometimes causing lasting damage that leads to epilepsy even after the infection clears.
Metabolic and Blood Chemistry Disruptions
Your brain is extremely sensitive to the chemical balance in your blood. When certain electrolytes or blood sugar levels swing far enough from normal, seizures can happen even in people with no history of epilepsy. These are called acute symptomatic seizures, and they typically stop once the underlying imbalance is corrected.
The key thresholds where seizures become likely:
- Sodium: Dangerously low sodium (below about 115 mEq/L) commonly triggers seizures. If the drop happens rapidly, seizures can occur at somewhat higher levels. On the high end, sodium levels above 160 mEq/L also cause neurological problems including seizures.
- Blood sugar: Seizures from low blood sugar typically happen when glucose drops below 40 mg/dL. This is relevant for people with diabetes who use insulin, as well as anyone with conditions that cause hypoglycemia. Extremely high blood sugar (600 to 800 mg/dL) can also provoke seizures, though through a different mechanism.
- Calcium: Low calcium levels between 5 and 6 mg/dL are a known seizure trigger. This can occur with kidney disease, parathyroid problems, or severe vitamin D deficiency.
People with kidney disease, liver failure, uncontrolled diabetes, or eating disorders face higher risk because these conditions make dangerous electrolyte and glucose swings more likely.
Alcohol and Sedative Withdrawal
Stopping heavy alcohol use abruptly is a well-known seizure trigger. Withdrawal seizures typically appear 24 to 48 hours after the last drink and are usually generalized tonic-clonic seizures, the type involving full-body convulsions and loss of consciousness. The risk is highest in people who have been drinking heavily for weeks or longer, and it increases with each subsequent withdrawal episode.
Withdrawal from sedative medications (particularly benzodiazepines and barbiturates) follows a similar pattern. The brain adapts to the constant presence of these substances by becoming more excitable to compensate. When the substance is suddenly removed, that excess excitability can spill over into a seizure. This is why medical supervision during detox from alcohol or sedatives is so important.
Stroke and Vascular Disease
Stroke doesn’t just raise seizure risk in the elderly. At any age, a stroke that damages brain tissue can become a seizure focus, an area of scarred or injured brain that generates abnormal electrical activity. Both ischemic strokes (blocked blood flow) and hemorrhagic strokes (bleeding in the brain) carry this risk, though hemorrhagic strokes tend to be more epileptogenic. Seizures can begin within the first week after a stroke or develop months to years later.
Other Notable Risk Factors
Several additional conditions raise seizure risk in meaningful ways. Brain tumors, whether cancerous or benign, can irritate surrounding brain tissue and cause seizures. In fact, a new-onset seizure in a middle-aged adult with no prior history sometimes leads to the discovery of a tumor. Autoimmune conditions that target the brain, such as autoimmune encephalitis, are an increasingly recognized cause. Sleep deprivation is a potent trigger in people who already have a seizure disorder and can occasionally provoke seizures in otherwise healthy individuals.
Eclampsia, a serious complication of pregnancy involving dangerously high blood pressure, causes seizures in pregnant or recently postpartum women. It typically develops after the 20th week of pregnancy and is one reason blood pressure monitoring during prenatal care is so routine.
HIV, neurocysticercosis (a parasitic brain infection common in parts of Latin America, Asia, and Africa), and certain medications that lower the seizure threshold (some antidepressants, antipsychotics, and stimulants) also contribute to seizure risk in specific populations.