No, you do not have to be born with epilepsy. While some forms are genetic and appear in childhood, epilepsy can develop at any age, and roughly 20 to 30 percent of all cases are directly caused by acquired factors like strokes, head injuries, or brain tumors. In about half of all epilepsy cases, no specific cause is ever identified. The condition has two peaks of new diagnoses: early childhood and after age 55.
Genetic Epilepsy Doesn’t Always Mean “Born With It”
Genetics play a role in a large share of epilepsy cases, but genetic epilepsy is not the same as being born with seizures. Many genetic epilepsy syndromes don’t show up until specific ages as the brain develops. Early onset absence epilepsy typically appears around age 2. Childhood absence epilepsy surfaces between ages 4 and 8. Juvenile myoclonic epilepsy, one of the most common genetic forms, doesn’t usually begin until around age 14, and onset can stretch into the mid-20s.
In these cases, a person carries the genetic predisposition from birth, but their brain doesn’t start producing seizures until it reaches a particular stage of development. Some genetic epilepsies also involve complex interactions between multiple genes and environmental triggers, meaning a genetic vulnerability alone may not be enough to cause the condition.
Common Causes of Epilepsy Later in Life
Epilepsy that develops in adulthood usually has a clear trigger. The most common ones include:
- Stroke. In adults over 35, stroke is the leading cause of new epilepsy. Damaged brain tissue can become a source of abnormal electrical activity.
- Traumatic brain injury. Car accidents, falls, and other head trauma can trigger epilepsy weeks, months, or even decades later.
- Brain tumors. Both cancerous and noncancerous growths can disrupt normal brain signaling.
- Infections. Meningitis, encephalitis, HIV, and certain parasitic infections can scar or inflame brain tissue enough to cause recurring seizures.
- Prenatal injury. Oxygen deprivation, infections during pregnancy, or poor nutrition can damage a baby’s developing brain, leading to epilepsy that appears in infancy or early childhood.
How a Brain Injury Becomes Epilepsy
When the brain is damaged by trauma, stroke, or infection, seizures don’t necessarily start right away. There’s often a “silent period” during which the injured brain tissue gradually reorganizes in ways that make it prone to generating abnormal electrical bursts. This process, called epileptogenesis, can take anywhere from six months to 30 years after the initial injury, though about 80 percent of post-traumatic epilepsy cases begin within the first two years.
This delay is part of what makes acquired epilepsy feel so unexpected. Someone can recover fully from a head injury, feel fine for months or years, and then have their first seizure seemingly out of nowhere. The injury set the process in motion long before symptoms appeared.
Risk After a Head Injury
Not everyone who hits their head develops epilepsy. The risk depends heavily on severity. A large nationwide study found that the 10-year risk of epilepsy after any traumatic brain injury was about 4 percent, compared to less than 1 percent in people without a head injury. But that number varies dramatically by injury type: mild concussions carried a 2.6 percent risk, while focal brain injuries (localized damage to a specific area) carried a 12.9 percent risk over 10 years. People with the most severe injuries were 16 times more likely to develop epilepsy than the general population.
Risk After Brain Infections
Central nervous system infections also carry meaningful epilepsy risk, though it varies by type and whether seizures occurred during the acute illness. Viral encephalitis poses the highest risk: people who had seizures during the infection faced a 22 percent chance of developing unprovoked seizures within 20 years. Even without early seizures, the 20-year risk after viral encephalitis was 10 percent. Bacterial meningitis with early seizures carried a 13 percent risk, dropping to about 2.4 percent without them. Milder viral meningitis didn’t raise the risk above the general population baseline.
Why Epilepsy Rates Rise in Older Adults
Epilepsy incidence is highest in the earliest years of life and then rises again after age 55, progressively increasing with each decade. The main drivers in older adults are strokes and neurodegenerative diseases. As blood vessels in the brain become more vulnerable to blockages or bleeds, and as conditions like Alzheimer’s disease cause accumulating damage to brain cells, the aging brain becomes increasingly susceptible to seizure activity. Cardiovascular risk factors like high blood pressure and high cholesterol appear to play a role in this connection, which is why some research has explored whether cholesterol-lowering medications might reduce the risk of epilepsy after stroke.
How Epilepsy Gets Diagnosed
The current international definition of epilepsy requires one of three things: at least two unprovoked seizures more than 24 hours apart, a single unprovoked seizure with a high enough recurrence risk (at least 60 percent over 10 years), or a recognized epilepsy syndrome identified through clinical features and testing. This means a single seizure after a night of heavy drinking or during a high fever doesn’t automatically count. The hallmark of epilepsy is a brain that has become prone to generating seizures on its own, without an obvious immediate trigger.
For people who develop seizures after a brain injury or stroke, the distinction matters. An early seizure within the first week after a head injury is considered a provoked response to acute damage. It’s the unprovoked seizures, the ones that come later after the brain has supposedly healed, that point to epilepsy.
The Bottom Line on Timing
Epilepsy is not a condition you have to be born with. It can begin at 2 months old, at 25 after a car accident, or at 70 after a stroke. Even the genetic forms often don’t produce their first seizure until years into childhood or adolescence. The brain’s vulnerability to epilepsy shifts across a lifetime, shaped by genetics, injuries, infections, and aging. About 1 in 100 children will be diagnosed with epilepsy by age 18, but new cases continue to accumulate well into old age.