Mood disorders seem to be more prevalent in people with epilepsy who have one or more relative with focal epilepsy.  The same is not true of those with relatives affected by generalised epilepsy.  The data was collected through interviews with the patients and their recall of events rather than through medical records.  The report also stated that mood disorders were under-diagnosed and therefore undertreated in patients with epilepsy making it all the more important that the medical profession identifies those at specific risk and delivers appropriate treatment.  Here is a link to a summary of the research published in Neurology Advisor.