Psychiatric comorbidity in epilepsy.
Many studies on psychiatric comorbidity in epilepsy have been performed using many different patient groups and diagnostic instruments. This methodological heterogeneity complicates comparison of the findings. In this article, psychiatric disorders in epilepsy are reviewed from the perspective of the DSM classification system. The empirical findings of axis I clinical disorders and axis II personality disorders are described separately. Furthermore, the existence and specificity of conditions such as interictal dysphoric disorder, interictal behavior syndrome, and psychosis of epilepsy are discussed. From the many studies that have been performed on this topic it can be learned that there is a need for well-controlled studies using representative patient groups and valid and standardized diagnostic instruments. So far, the majority of the studies have concerned axis I disorders; relatively little research has been performed on axis II personality disorders. More research on personality disorders, as well as on the relative contributions of the different (brain- and non-brain-related) factors to the relationship between epilepsy and psychiatric disorders, is recommended.