Juvenile myoclonic epilepsy develops between ages 12 and 18. People with the disorder tend to have seizures that cause jerking in the shoulders or arms. Generalized tonic-clonic seizures and absence seizures may be present along with myoclonic seizures. Seizures often occur early in the morning.

People with juvenile myoclonic epilepsy have normal intelligence and do not have other brain or nerve disorders. While a family history of myoclonic seizures is present in about half of the people with the disorder, the exact cause is unknown. Most people require lifelong treatment with medication.