Familial clustering of epilepsy and behavioral disorders: evidence for a shared genetic basis

Purpose: To examine whether family history of unprovoked seizures is associated with behavioral disorders in epilepsy probands, thereby supporting the hypothesis of shared underlying genetic susceptibility to these disorders.

Methods: We conducted an analysis of the 308 probands with childhood onset epilepsy from the Connecticut Study of Epilepsy with information on first-degree family history of unprovoked seizures and of febrile seizures whose parents completed the Child Behavior Checklist (CBCL) at the 9-year follow-up. Clinical cutoffs for CBCL problem and Diagnostic and Statistical Manual of Mental Disorders (DSM)-Oriented scales were examined. The association between first-degree family history of unprovoked seizure and behavioral disorders was assessed separately in uncomplicated and complicated epilepsy and separately for first-degree family history of febrile seizures. A subanalysis, accounting for the tendency for behavioral disorders to run in families, was adjusted for siblings with the same disorder as the proband. Prevalence ratios were used to describe the associations.

Key findings: In probands with uncomplicated epilepsy, first-degree family history of unprovoked seizure was significantly associated with clinical cutoffs for Total Problems and Internalizing Disorders. Among Internalizing Disorders, clinical cutoffs for Withdrawn/Depressed, and DSM-Oriented scales for Affective Disorder and Anxiety Disorder were significantly associated with family history of unprovoked seizures. Clinical cutoffs for Aggressive Behavior and Delinquent Behavior, and DSM-Oriented scales for Conduct Disorder and Oppositional Defiant Disorder were significantly associated with family history of unprovoked seizure. Adjustment for siblings with the same disorder revealed significant associations for the relationship between first-degree family history of unprovoked seizure and Total Problems and Aggressive Behavior in probands with uncomplicated epilepsy; marginally significant results were seen for Internalizing Disorder, Withdrawn/Depressed, and Anxiety Disorder. There was no association between family history of unprovoked seizure and behavioral problems in probands with complicated epilepsy. First-degree family history of febrile seizure was not associated with behavioral problems in probands with uncomplicated or in those with complicated epilepsy.

Significance: Increased occurrence of behavioral disorders in probands with uncomplicated epilepsy and first degree family history of unprovoked seizure suggests familial clustering of these disorders. This supports the idea that behavioral disorders may be another manifestation of the underlying pathophysiology involved in epilepsy or closely related to it.