Seizures in adults can appear suddenly and often without warning. For many people, the first episode is unexpected, which naturally leads to concern about what caused it and whether it could happen again.
At its core, a seizure happens when there is a sudden disruption in normal brain activity. This interruption affects how signals are sent between brain cells, which can briefly change movement, awareness, behaviour, or sensation.
While epilepsy is a common reason, it is not the only explanation. In fact, seizures can be triggered by a range of short-term or underlying medical issues that need proper investigation.
This guide breaks down the most common causes of seizures in adults, what symptoms to look out for, and when medical support is needed.
What is a seizure?
A seizure is a short-lived change in how the brain works due to unusual electrical activity. Depending on the area of the brain affected, symptoms can range from subtle “blank moments” to full loss of consciousness and involuntary movements.
Some seizures affect just one part of the brain (focal seizures), while others involve both sides at once (generalised seizures).
Not every seizure means epilepsy. Epilepsy is only diagnosed when there is a tendency for recurrent, unprovoked seizures over time (NICE NG217).
You can read more about diagnosis and types of epilepsy here.
What causes seizures in adults?
There isn’t a single cause. In adults, seizures are usually linked to one of several underlying factors. Some are long-term neurological conditions, while others are temporary or reversible.
Epilepsy
Epilepsy is one of the most recognised causes of recurring seizures. It is a condition where the brain has a tendency to produce seizures without an immediate trigger.
However, many adults experience a seizure first before any diagnosis is made. That first event is often what leads to investigation.
Stroke or brain injury
One of the more common causes of new seizures in adults is damage to the brain. This may include:
- Stroke
- Head injury
- Brain surgery
- Tumours or lesions
When brain tissue is disrupted, the normal flow of electrical signals can be affected, increasing the likelihood of a seizure. Clinical neurology literature highlights structural causes as a key category in first-time adult seizures (BMJ clinical review).
Alcohol and withdrawal
Alcohol can play a significant role in seizure activity, particularly during withdrawal after heavy or prolonged use. It can lower the brain’s seizure threshold, making episodes more likely.
Metabolic changes
Temporary changes in the body’s chemistry can also trigger seizures. These might include:
- Low blood sugar
- Low sodium levels
- Severe dehydration
- Liver or kidney problems
In these cases, the seizure is often linked to an underlying medical issue that needs correction.
Infection affecting the brain
Infections such as meningitis or encephalitis can irritate brain tissue. Although less common, they can cause seizures and usually come with other symptoms such as fever, headache or confusion.
Sleep deprivation and stress
Lack of sleep is a well-known trigger, particularly in people who already have a tendency towards seizures. Stress can also play a role, although it is rarely the sole cause.
Symptoms of epileptic seizures
Seizure symptoms vary depending on the type and severity, but common signs include:
- Sudden loss of awareness
- Staring into space or “zoning out”
- Uncontrolled jerking or shaking
- Confusion afterwards
- Strange sensations such as tingling, déjà vu or rising feelings in the stomach
- Memory gaps around the event
Some seizures are very subtle and may only look like a brief pause or change in awareness.
More detail on symptoms and diagnosis can be found here.
When to seek medical help
A seizure should always be taken seriously, especially if it is the first one.
Medical advice should be sought if:
- It is the first known seizure
- The seizure lasts longer than a few minutes
- There is difficulty breathing afterwards
- The person does not recover as expected
- Injuries occur during the episode
- Seizures happen repeatedly
Even if recovery seems complete, a first seizure usually requires further investigation to understand the cause.
How seizures are diagnosed
Diagnosis is not based on a single test. Instead, clinicians look at the full picture.
This may include:
- A description of the event (often from someone who witnessed it)
- Medical history
- Brain scans such as MRI or CT
- EEG tests to look at brain activity
- Blood tests to check for metabolic causes
The aim is to understand whether the seizure was triggered by something temporary or linked to an ongoing neurological condition.
Treatment and management
Treatment depends entirely on the cause.
Treating the underlying trigger
If the seizure is caused by something reversible, such as infection, low blood sugar or alcohol withdrawal, treatment focuses on resolving that issue first.
Anti-seizure medication
If epilepsy is diagnosed, medication may be prescribed to reduce the likelihood of further seizures.
Lifestyle factors
For some people, managing triggers can help reduce risk:
- Prioritising regular sleep
- Avoiding alcohol excess
- Managing stress levels
- Taking medication consistently if prescribed
Living with epilepsy
If seizures continue or a diagnosis of epilepsy is made, long-term support is often needed to help manage symptoms and reduce disruption to daily life.
You can find out more about how to live with epilepsy here.
Additionally, get in touch with our team for a specialist neurological assessment.
Key takeaways
Seizures in adults are a symptom, not a diagnosis. They can be linked to epilepsy, but also to stroke, brain injury, metabolic changes, infections or temporary lifestyle triggers.
A first seizure should always be checked by a specialist to understand what caused it and whether further treatment is needed.
