Epilepsy refers to a spectrum of neurological disorders that involve recurring seizures. It’s also possible to have nonepileptic spells — events that aren’t caused by an epileptic disorder. Epilepsy has many different causes.

Epilepsy can be broken into two broad categories depending on whether the cause of seizure activity is known or unknown. When the cause of a person’s epilepsy is known, it’s called symptomatic or secondary epilepsy. Epilepsy with unknown causes is referred to as idiopathic or cryptogenic epilepsy. Some epilepsy is inherited, or due to a genetic mutation (change). In other cases, epilepsy is structural in origin, resulting from brain damage or abnormal brain development. Epilepsy isn’t contagious.

Forms of epilepsy caused by a genetic mutation or brain damage that occurred during birth or pregnancy tend to show up and be diagnosed during childhood. Other types can be more common later in life.

Genetic Causes of Epilepsy

About 4 percent of people — or about 1 in 26 — will develop epilepsy at some point. Having a first-degree relative (parent, child, or sibling) with epilepsy increases your risk of epilepsy 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’s thought to have a genetic component. In fact, genes are known to play a role in about 30 percent to 40 percent of epilepsy cases.

Many cases of epilepsy are caused by a mutation, usually on a gene responsible for the activity 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 a genetic mutation will never have seizures or develop epilepsy. This indicates that genes aren’t the only factor — environmental factors also play a role.

Many types of epilepsy can be inherited. Known genetic causes of epilepsy include:

• Angelman syndrome
• Doose syndrome
• Down syndrome
• Lennox-Gastaut syndrome
• Panayiotopoulos syndrome

There’s also an association between autism spectrum disorder and epilepsy. About one-third of people with autism also have epilepsy. Certain genetic syndromes, including Rett, fragile X, Prader-Willi, and Angelman syndromes, are linked with both seizures and autism.

In children with autism, intellectual disability increases the risk of epilepsy. A study published in the journal Biological Psychiatry reported that about 22 percent of autistic children with intellectual disability develop epilepsy, whereas 8 percent of those without intellectual problems begin having seizures. No specific type of epilepsy or severity of seizure is associated with autism spectrum disorder. Altogether, the relationship between autism and epilepsy is poorly understood.

Some researchers believe there may be a genetic component to all forms of epilepsy. In this theory, everyone who has seizures is genetically predisposed to them. If that’s the case, then seizures that start after a brain injury or other structural change may be due to both the injury or change and the person’s genetic predisposition to seizures. This theory might explain why a brain injury might lead to epilepsy in one person but not another.

Structural Causes of Epilepsy

Abnormalities in the brain’s structure or metabolism (the chemical process of breaking down substances) can cause seizures. Some are considered epileptic seizures, and others are considered nonepileptic seizures.

Structural problems may be congenital (present at birth) or caused later by a brain tumor or traumatic brain injury, perhaps the result of a head injury from a car crash or another accident. Strokes, brain infections such as meningitis, and alcohol or drug abuse can also cause a structural problem that leads to seizure activity. In situations like these, normal brain structure is distorted or disrupted, resulting in abnormal brain waves that trigger seizures.

In addition, more than 200 metabolic diseases are known to cause epilepsy. Metabolic problems can deprive brain cells of the glucose they require for fuel or reduce levels of electrolytes such as sodium or potassium — minerals the body needs to function properly. The result is abnormal brain waves that cause seizures.

Inflammation, which may be the result of a traumatic brain injury or a chronic inflammatory condition such as lupus, can also flood the brain with proteins that may trigger seizures.

Congenital brain damage may be caused by malnutrition, infection, trauma, or drug use during pregnancy. It may also be due to a genetic defect. Children who are born prematurely or deprived of oxygen during birth can develop brain damage that causes seizures. Many newborns outgrow their seizures, but a small number have seizures that can be lifelong and difficult to treat.

Typically, 50 percent to 70 percent of children who have epilepsy eventually achieve seizure remission (having no seizures or symptoms). The chances for remission are higher if seizures aren’t frequent and are adequately treated by antiepileptic drugs, as well as if there are no underlying neurological problems.

Other Risk Factors for Epilepsy and Seizures

It’s important to keep in mind other risk factors for epilepsy. Different types of seizures might have different risk factors.

For instance, major risk factors for absence seizures (in which the person experiences a loss of consciousness) include:

• Age — These seizures are more frequent in children between ages 4 and 14.
• Biological sex — Females are more at risk.
• Genes — Absence seizures tend to run in families.

Sometimes, older age can be a risk factor for epilepsy or seizure. For example, Alzheimer’s disease is associated with seizure activity and epilepsy.

Epilepsy With Unknown Causes

If your doctor can’t identify the source of your epilepsy, you’ll be diagnosed with idiopathic or cryptogenic epilepsy. “Idiopathic” comes from Greek words meaning “a disease of its own kind.” It means that doctors don’t know the cause. Similarly, “cryptogenic” comes from Greek words meaning “hidden cause.”

Approximately 50 percent of all epilepsies have unknown causes. Certain types of seizures may stem from a scar or irritation on the brain, but the scar is undetectable by an MRI. As brain imaging techniques improve, more causes of seizures will be identified.

Talk With Others Who Understand

On MyEpilepsyTeam, the social network for people with epilepsy, more than 122,000 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? Share your experience in the comments below, or start a conversation by posting on your Activities page.