Adult-Onset Seizures: Causes, Outlook, and More

Medically Reviewed By Nancy Hammond, M.D.
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Sometimes, people experience a seizure for the first time in adulthood. This can occur due to many different causes, including conditions and injuries that affect brain functioning. The nerve cells of the brain coordinate and produce chemical and electrical signals that help to regulate the body’s behavior and functions. However, when something damages the nerve cells or affects their function, it can provoke a seizure. This is because affected nerve cells may produce irregular or more frequent signals, causing seizure symptoms.

Seizures that occur for the first time during adulthood can be known as “adult-onset” seizures or epilepsy. Research suggests that adult-onset seizures may be most common in younger and middle-aged adults than in older adults.

This article will explain what causes seizures in adults for the first time, as well as the diagnostic process for seizures and epilepsy. It will also discuss the symptoms of seizures in adults and when to seek medical help.


The back of a person's head and shoulders overlaid with blurry lights
Jesse Weinberg/Stocksy United

Seizures can occur for the first time in adulthood due to the development of epilepsy. However, a singular seizure can occur due to illness or injury that does not relate to epilepsy. These singular seizures are known as “provoked seizures.”

Some triggers for epilepsy and provoked seizures can be similar. However, epilepsy has other features. An epilepsy diagnosis typically requires a person to experience at least two seizures, per the Centers for Disease Control and Prevention (CDC).

Learn more about the causes and development of seizures and epilepsy.

Below are the principal causes of adult-onset seizures.

Nervous system infection

Infections that develop in the central nervous system may lead to the onset of epilepsy. Such infections can include bacterial, viral, fungal, and parasitic infections.

This is because some infections may harm the nervous system, including the nerves and brain tissue, or trigger immune and inflammatory responses that cause further damage and impact brain function.

Examples of infectious pathogens that may affect the central nervous system include:

High alcohol intake

According to the Epilepsy Foundation, small amounts of alcohol do not cause seizures. However, a large intake of alcohol in a short time can lead to seizures. Mixing consumption of alcohol with some drugs, including some prescription drugs such as antibiotics, can also cause seizures.

Additionally, chronic alcohol use disorder may relate to the development of epilepsy for some.

However, it is still possible to experience alcohol-related seizures without having chronic alcohol use disorder. For example, some people may experience a seizure after consuming a large amount of alcohol in a short time. The seizure may be due to the effects of alcohol withdrawal.

Alcohol or substance misuse may also indirectly lead to seizures if intoxication causes falls which lead to head injury.

Learn more about alcohol use disorder, including prevention, treatment, and complications.

Substance intake and withdrawal

An adult may experience a seizure for the first time due to the use of certain substances, including prescription and nonprescription drugs, and some poisonous substances. Intoxication and withdrawal from these substances may also link to first-time seizures.

Examples of substances that may commonly lead to seizures as a complication include:

  • stimulants, such as cocaine and methamphetamine
  • diphenhydramine (Benadryl)
  • tramadol (ConZip, Ultram)
  • antibiotics, such as isoniazid
  • antidepressants, such as bupropion (Wellbutrin, Forfivo, others)
  • psychoactive drugs
  • opioids
  • carbon monoxide
  • cyanide


Withdrawal from certain substances, such as alcohol and drugs can lead to seizures. Additionally, withdrawal can also induce status epilepticus, a medical emergency that occurs when seizures last for 5 minutes or more.

Withdrawal from the following substances may lead to seizures:

  • alcohol
  • opioids
  • benzodiazepines
  • gamma-hydroxybutyrate (GHB)
  • stimulants

Brain injury

A traumatic brain injury (TBI), including concussions, may lead to seizures and epilepsy. Clinicians may refer to these as “post-traumatic seizures.”

The CDC notes that seizures can onset from a TBI anywhere from moments after the injury to years later. In fact, a 2010 study observes that around 1 in 10 teenagers and adults hospitalized for TBIs developed epilepsy within 3 years of their injury.

Additionally, the CDC suggests that the more severe a TBI is, the higher a person’s chance of developing epilepsy. However, other factors may also affect whether a person develops epilepsy after a TBI. These factors include the person’s age and any underlying medical conditions.

Learn more about the prevention and treatment of concussion and TBI.


Sometimes, seizures and epilepsy can occur as a complication of a stroke. This is because strokes may impair function and blood flow in the brain. These impairments cause changes to the brain’s electrical activities.

The onset of post-stroke seizures ranges from hours after a stroke to a month or more.

If you experience your first seizure after a stroke, the stroke may have induced it.

Brain tumor

Brain tumors may provoke seizures if the tumor affects the function and processing of the brain. Seizures are one of the most common symptoms of brain tumors.

Seizures may occur as an initial symptom of any type of brain tumor, including benign (noncancerous) and malignant (cancerous) tumors.

Removing the tumor may be enough to resolve tumor-related seizures if there is no other cause.

Other brain and cerebrovascular conditions

Cerebrovascular disease (CVD) refers to conditions that affect the blood flow and vessels in the brain.

Researchers from a 2021 study suggest that first-time seizures in adults most commonly result from CVD.

Other conditions that affect the brain may also contribute to the development of seizures, including:

  • vasculitis
  • cerebral small vessel disease
  • encephalitis, a type of infection of the brain
  • brain edema
  • congenital anomalies, such as:
    • structural differences of the brain
    • focal cortical dysplasia

Unknown cause

Sometimes, it is unclear what triggers seizures in adults for the first time. Clinicians may refer to such cases as idiopathic seizures or idiopathic epilepsy syndrome.

The same 2021 study suggests that idiopathic epilepsy was the second most common cause of first-time seizures in adults. Idiopathic epilepsy syndrome may be even more common in younger adults.

Idiopathic seizures and epilepsy may have a genetic cause.

When to seek medical help

Not all instances of seizures require emergency medical care. However, many circumstances require immediate clinical help.

If you suspect that it could be the person’s first seizure, call 911 or seek emergency medical attention.

Additionally, call 911 or seek emergency medical care for seizures with the following characteristics:

  • the person has difficulty breathing or regaining consciousness after the seizure
  • the person is unresponsive for longer than 5 minutes after a seizure
  • the seizure lasts for more than 5 minutes
  • another seizure occurs soon after the first one
  • the person becomes hurt or injured during or after the seizure
  • the seizure happens while the person is in water
  • the person has an underlying health condition or is pregnant


To diagnose your symptoms and the cause of seizures, a doctor will start by asking about your symptom and medical history, as well as your family’s medical history. Additionally, they may conduct a physical exam to check your health and observe any other possible health conditions that may cause your symptoms.

It may be helpful to bring someone with you who witnessed your seizure if you experienced a loss of consciousness or memory at the time.

A doctor may then refer you to a specialist, arrange diagnostic testing, or both. Diagnostic testing may include:

Learn more about the symptoms and treatment of seizures.


Conditions affecting the brain and central nervous system can cause first-time seizures in adults. These conditions can trigger one-time, provoked seizures or the onset of epilepsy.

Conditions that may lead to seizures include stroke, central nervous system infection, TBI, or brain tumors. Sometimes, the cause is unknown.

Seek emergency medical care for anyone you suspect could be experiencing their first-ever seizure.

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Medical Reviewer: Nancy Hammond, M.D.
Last Review Date: 2022 Oct 28
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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