Epilepsy has many different causes, and sometimes doctors never find one
Epilepsy starts when something disrupts the electrical signals in your brain. That disruption can come from a head injury, a stroke, a brain tumor, an infection, a genetic condition you were born with, or sometimes nothing doctors can identify. About one-third of people with epilepsy have a known cause; the other two-thirds have what doctors call idiopathic epilepsy, meaning the cause is unknown. Knowing the cause matters because it can change how the seizures are treated and what to expect over time.
The brain works by sending electrical signals between neurons. Epilepsy happens when those signals misfire in a way that triggers repeated seizures. A single seizure does not mean you have epilepsy—it means something disrupted your brain's electrical activity that one time. Epilepsy is the tendency to have seizures over and over, usually without a clear trigger each time.
Key Takeaways
- Head injuries, strokes, brain tumors, and infections are common identifiable causes of epilepsy, but many people with epilepsy have no known cause.
- Some people are born with genetic conditions that make seizures more likely, and these can run in families.
- Brain damage from lack of oxygen at birth, premature birth, or severe jaundice in infants can lead to epilepsy later in childhood.
- Knowing the cause of your epilepsy can help your doctor choose the right treatment and predict how the condition may change over time.
Head injuries and brain trauma
A serious head injury is one of the most common causes of epilepsy in adults. The risk is highest in the first few years after the injury, but seizures can start months or even years later. The severity of the injury matters—a mild concussion carries much lower risk than a traumatic brain injury with bleeding or bruising inside the skull.
Repeated head impacts, even if each one seems minor, can also increase seizure risk over time. This is why people who play contact sports or have occupations with fall risk are sometimes counseled about the long-term consequences. If you have had a significant head injury and later develop seizures, tell your doctor about the injury—it helps them understand what type of epilepsy you have.
Stroke and other blood vessel problems in the brain
A stroke happens when blood flow to part of the brain is blocked or a blood vessel ruptures. The brain tissue that loses blood supply can be damaged permanently, and that scarred tissue can become a source of seizures. Stroke is the most common cause of epilepsy in older adults, particularly in people over 60.
Other blood vessel problems can also trigger epilepsy, including bleeding in the brain, abnormally formed blood vessels, or blood clots. If you have had a stroke or been told you have a blood vessel abnormality in your brain, your doctor will monitor you for seizure risk and may start preventive treatment depending on the type and location of the damage.
Brain tumors and other growths
A tumor in the brain—whether it started there or spread from cancer elsewhere in the body—can cause seizures. The tumor itself can irritate the surrounding brain tissue, or swelling around the tumor can disrupt electrical signals. Seizures are sometimes the first sign that someone has a brain tumor, which is why a first seizure in an adult always warrants imaging to rule out a tumor.
Not everyone with a brain tumor develops seizures, and not all seizures in someone with a tumor are caused by the tumor itself. Treatment of the underlying tumor—surgery, radiation, or chemotherapy—sometimes reduces or stops the seizures, though some people continue to have them even after the tumor is treated.
Infections and inflammation of the brain
Infections that reach the brain tissue, such as meningitis or encephalitis, can cause seizures during the acute illness and sometimes lead to long-term epilepsy afterward. Viral infections like herpes simplex virus, measles, or COVID-19 have been linked to seizures. Bacterial infections, fungal infections, and parasitic infections can all damage brain tissue in ways that trigger seizures.
The inflammation from these infections can scar the brain, and scar tissue is prone to generating seizures. Even after the infection is treated and cleared, the person may continue to have seizures months or years later. If you have had meningitis, encephalitis, or another serious brain infection, your doctor may discuss seizure risk with you and what signs to watch for.
Genetic and developmental conditions present from birth
Some people inherit genes that make seizures more likely. These genetic forms of epilepsy can run in families, though not everyone who carries the gene will develop seizures. Genetic testing can identify some of these conditions, and knowing which gene is involved can help guide treatment choices because certain medications work better for certain genetic types.
Developmental conditions that affect the brain's structure from birth can also cause epilepsy. These include conditions like tuberous sclerosis, where benign tumors grow in the brain; cortical malformations, where the brain's surface did not form normally; and metabolic disorders that affect how the brain uses energy. Some of these are diagnosed before seizures start through prenatal screening or imaging; others are discovered only after a seizure occurs.
Brain damage from lack of oxygen or difficult birth
Infants who do not get enough oxygen during birth or in the hours after birth can develop brain damage that leads to seizures in childhood or adulthood. Premature birth, severe jaundice that goes untreated, or complications during labor can all reduce oxygen to the brain. The damage may be visible on brain imaging as areas of scarring or abnormal development.
Not every infant with birth-related oxygen deprivation develops epilepsy, but the risk is higher than in the general population. If you or your child had a difficult birth or were told about oxygen deprivation, mention this to your doctor if seizures develop later, as it provides important context for diagnosis and treatment.
Aging and degenerative brain conditions
As people age, the risk of developing epilepsy increases, particularly after age 60. This is often because of stroke, dementia, or other age-related changes in the brain. Conditions like Alzheimer's disease, Parkinson's disease, and other forms of dementia can increase seizure risk, though seizures are not inevitable in these conditions.
The seizures in older adults may look different from seizures in younger people—they can be subtle, brief, or occur mainly during sleep. If an older person develops new seizures, doctors investigate whether there is an underlying condition like stroke or dementia that needs treatment, because treating the underlying cause sometimes helps control the seizures.
Frequently Asked Questions
Can epilepsy be caused by stress or emotional trauma?
Stress and emotional trauma do not cause epilepsy, though they can trigger seizures in someone who already has the condition. The underlying cause of epilepsy is always a physical change in the brain—whether from injury, infection, genetics, or something else. Stress management is still important for people with epilepsy because reducing stress can help reduce seizure frequency.
If my parent has epilepsy, will I definitely get it?
Not necessarily. Even if epilepsy runs in your family, inheriting the genetic tendency does not may provide you will develop seizures. Some people with the genetic risk never have a seizure. If you have a family history of epilepsy, tell your doctor, but having relatives with epilepsy does not mean you will develop it.
Can a single seizure turn into epilepsy?
A single seizure does not automatically become epilepsy. Epilepsy is defined as a tendency to have repeated seizures. However, if you have had one seizure, your doctor may recommend brain imaging and other tests to look for an underlying cause that could lead to more seizures in the future.
Does epilepsy get worse over time?
This depends on the cause and type of epilepsy. Some forms are stable and do not worsen. Others improve with age or with treatment. Some people's seizures become harder to control over time. Your doctor can discuss what to expect based on your specific type of epilepsy and what is causing it.
If doctors cannot find a cause, does that mean my epilepsy is less serious?
Unknown cause does not mean less serious. Idiopathic epilepsy—epilepsy with no identified cause—can range from mild to severe. The seriousness depends on how often seizures occur, how long they last, and how well they respond to treatment, not on whether doctors found the underlying cause.