Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental condition characterized by patterns of inattention and/or hyperactivity-impulsivity that interfere with functioning or development. Seizures are transient occurrences of signs or symptoms due to abnormal excessive or synchronous neuronal activity in the brain, often associated with epilepsy. While ADHD does not directly cause seizures in adults, the relationship is one of frequent co-occurrence, known as comorbidity. This suggests a shared underlying vulnerability between the two conditions.
Understanding Comorbidity: Why ADHD and Seizures Co-Occur
The connection between Attention-Deficit/Hyperactivity Disorder and seizures is statistical rather than causative. Studies consistently show that adults with epilepsy are significantly more likely to also have ADHD than the general population. Up to 20% of adults with epilepsy report symptoms of ADHD, a rate four times higher than the approximate 4.4% seen in the general adult population.
Individuals with ADHD are also at a higher risk for seizures compared to those without the condition. This bidirectional relationship points toward a common underlying biological factor that predisposes an individual to both disorders. This shared vulnerability suggests that the neurobiological differences present in ADHD may slightly lower the baseline “seizure threshold,” making the person’s brain more susceptible to electrical disturbances.
Shared Neurological Underpinnings
The frequent co-occurrence of ADHD and seizures is rooted in shared irregularities in brain structure and function. Both conditions involve complex networks within the brain, and the areas responsible for attention and impulse control often overlap with those that regulate electrical stability. Specifically, disruptions in the frontal lobe, which governs executive functions like attention and decision-making, are implicated in both disorders.
The dysregulation of specific neurotransmitter pathways is another shared factor. ADHD is primarily linked to imbalances in dopamine and norepinephrine pathways, which are critical for attention, motivation, and impulse control. Imbalances in these same systems can affect overall neuronal excitability, which in turn influences the brain’s seizure threshold. A shared genetic vulnerability may also predispose an individual to both conditions.
Furthermore, research using advanced imaging has shown that adults with both ADHD and epilepsy may have structural differences. These include reduced volume in areas like the thalamus and the brainstem compared to those with epilepsy alone. The thalamus is a deep brain structure involved in regulating consciousness and alertness, and its reduced volume may contribute to both inattention symptoms and electrical instability.
Medication Considerations for Adults with Both Conditions
Managing ADHD in an adult with a history of seizures requires careful consideration of medication to avoid increasing seizure frequency. Historically, there was a concern that stimulant medications, such as methylphenidate (Ritalin) and amphetamines (Adderall), might lower the seizure threshold. This concern stemmed from early warnings and observations of seizures in cases of stimulant abuse or overdose.
However, recent large-scale observational studies challenge this long-held assumption. They suggest that prescribed therapeutic doses of ADHD medications do not increase the risk of seizures in people with epilepsy. In fact, some research has indicated that people with both conditions may experience a lower risk of seizures while they are consistently taking their ADHD medication compared to periods when they are not. This potential protective effect may be because the medication effectively treats a shared underlying biological mechanism.
Non-stimulant options are also considered, but they carry their own specific risks. The non-stimulant Bupropion (Wellbutrin), which is sometimes used off-label for ADHD, has a well-documented risk of significantly lowering the seizure threshold and is often contraindicated for use in patients with a history of seizures. When both conditions are present, coordinating care between a neurologist and a psychiatrist is necessary to select the most appropriate ADHD medication that avoids negative interactions with anti-epileptic drugs (AEDs) and maintains seizure control.