Psychiatric symptoms provide potential insights into the pathophysiology of psychiatric conditions in epilepsy patients. Evaluating the psychiatric effects of newer AEDs is complicated by several important factors including (a) the relatively high rate of mood and anxiety disorders in persons with pharmacoresistant epilepsy, and (b) the variety of methods used to assess the occurrence and severity of psychiatric symptoms. Clinical trials to assess adverse psychiatric effects of AEDs need a control group to adjust for the spontaneous occurrence of symptoms, as well as to demonstrate potential positive psychotropic effects. The follow-up should be long enough to differentiate between drug-related effects and the natural course of the comorbid disorder. Psychiatric problems should be defined using appropriate instruments as well as self-report.