Epilepsy is a group of neurological conditions characterized by recurring seizures. These seizures happen when there’s a sudden burst of electrical activity in the brain. While some events that look like seizures aren’t due to epilepsy, a diagnosis of epilepsy means there’s an ongoing risk for repeated seizures.

But what causes epilepsy to develop? The answer isn’t always straightforward — epilepsy can have many different origins, and for some people, the cause remains unknown.

Doctors generally classify epilepsy based on whether the underlying cause is known. Sometimes, epilepsy stems from clear factors like genetic changes, brain injuries, or developmental differences (when the brain doesn’t form or function in the usual way, often starting before birth).

In other cases, no specific cause can be identified, even after thorough testing. Knowing what might cause epilepsy helps guide treatment options and reduce risks.

Below, we’ll explore the most common causes of epilepsy, including genetic risks, structural changes in the brain, and other contributing factors. We’ll also discuss what it means if your epilepsy has no identifiable cause.

Genetic Causes of Epilepsy

Almost 4 percent of people — or about 1 in 26 — will have epilepsy during their lifetime. Having a first-degree relative (parent, child, or sibling) with epilepsy increases your risk about threefold. It’s common for family members to have different types of epilepsy from one another. When a disorder or disease tends to run in families, it likely has a genetic link. In fact, genes are known to play a role in about 30 percent of epilepsy cases.

Many cases of epilepsy are caused by mutations (changes), usually on genes responsible for the communication of neurons (nerve cells) in the brain. Mutations there cause the bursts of electrical activity that lead to symptoms associated with seizures.

However, many people with these gene changes will never have seizures or develop epilepsy. This indicates that genes aren’t the only factor — environmental factors also play a role. These may include brain injuries, infections, prenatal complications, or exposure to certain toxins.

Genes aren’t the only factor involved in epilepsy — environmental factors also play a role.

Some types of epilepsy can be passed down in families. Known genetic causes of epilepsy include:

• Angelman syndrome — Affects the nervous system, causing developmental delays, balance problems, and seizures
• Doose syndrome — Causes sudden muscle jerks and drop seizures, mostly in young children (also called myoclonic-atonic epilepsy)
• Lennox-Gastaut syndrome — Involves multiple types of seizures and intellectual disability and begins in early childhood
• Dravet syndrome — Begins in infancy, with prolonged seizures often triggered by fever

There’s also an association between autism spectrum disorder and epilepsy. About 20 percent to 40 percent of autistic children eventually develop epilepsy. This risk is greater than that of the general population. Certain genetic conditions, including Rett, fragile X, Prader-Willi, and Angelman syndromes, are linked to both seizures and autism.

Autistic children who also have an intellectual disability have a higher risk of epilepsy. One study found epilepsy in about 22 percent of autistic people who also have an intellectual disability, compared with 8 percent of those without an intellectual disability. Researchers believe that more severe forms of epilepsy may be more strongly associated with autism, but additional studies are needed.

Some researchers think all forms of epilepsy may have a genetic component. In this theory, genetics makes everyone who has seizures more likely to experience them. Therefore, seizures that start after a brain injury or other structural change may be due to both the injury or change and the person’s genetics. This idea might help explain why some people develop epilepsy after a brain injury but others don’t.

Structural Causes of Epilepsy

Abnormalities in the brain’s structure can also cause seizures. These problems can be congenital (present at birth) or develop later from a brain tumor or traumatic brain injury, such as a head injury from a car accident.

Congenital brain damage can happen due to poor nutrition or infection during pregnancy. Being born prematurely (early) or losing oxygen at birth can cause brain damage and lead to seizures.

Typically, about 60 percent of children with epilepsy eventually achieve seizure remission (being symptom- and seizure-free). The chances for remission are higher if seizures aren’t complicated and don’t arise from underlying neurological problems. The chances are lower if seizures don’t respond to anti-seizure medications.

Other causes — such as stroke or brain infections like meningitis — can also affect the brain and lead to seizures. In autoimmune encephalitis, the body’s own immune system attacks the brain by mistake, which can lead to seizures or epilepsy. Strokes are the most common cause of new epilepsy in older adults. It’s not always clear why epilepsy develops after a stroke, but recent research suggests that changes in brain cell pathways and a buildup of harmful substances may play a role.

Other Risk Factors for Epilepsy and Seizures

Other risk factors can also raise the risk of epilepsy. Different types of seizures may have different risk factors. For example, major risk factors for absence seizures (brief loss of consciousness) include:

• Age — These seizures are more common in children ages 4 to 14.
• Sex — Females are at increased risk, according to Mayo Clinic.
• Genes — Absence seizures tend to run in families.

Older age can also raise the risk of epilepsy or seizures. For example, Alzheimer’s disease is linked to seizure activity and epilepsy.

More than 200 metabolic diseases can cause epilepsy. These medical conditions can deprive brain cells of the glucose (blood sugar) they need for fuel or upset the balance of electrolytes (minerals such as sodium or calcium) that the body needs to function properly. These changes can trigger seizures.

Epilepsy With Unknown Causes

Sometimes, healthcare providers can’t find a clear cause for epilepsy. This is called “epilepsy of unknown cause.” About 50 percent of people with epilepsy have this type. As medical testing improves, doctors hope to better understand what causes these seizures.

Talk With Others Who Understand

MyEpilepsyTeam is the social network for people with epilepsy and their loved ones. On MyEpilepsyTeam, members come together to ask questions, give advice, and share their stories with others who understand life with epilepsy.

Have you identified what caused epilepsy in you or your child? Are you interested in learning more about the genetic or structural causes of epilepsy? Share your experience in the comments below, or start a conversation by posting on your Activities page.