Psychiatric comorbidities have been reported in some people with epilepsy and may range from depression to anxiety to acute psychosis and schizophreniform disorders. They seem to occur in people with epilepsy much more frequently as compared to the general population. Up to 30-70% of people with temporal lobe epilepsy can have depression, anxiety or behavioral issues. New onset psychiatric comorbidities may arise after epilepsy surgery.
The term comorbidity has to be used and interpreted with caution. By definition, it refers to the occurrence of two conditions in an individual that is greater than would be expected by chance, however it does not imply what the underlying cause is or which condition may have lead to the other. In other words, the two disorders might co-occur by chance or they could share genetic, environmental, or other causes. The question what is the hen, what is the egg is crucial in this context.
There is increasing evidence that depression and anxiety may be already present at seizure-onset or even precede the first seizure. In several studies, depression was found to be a strong risk factor for seizure occurrence and epilepsy. It is likely that psychiatric comorbidities are part of the same network disturbances as they are found in epilepsy.
If comorbidities are identified in persons with epilepsy, choosing an antiseizure drug is critical because some drugs may help both seizures and mood disorders (e.g. valproate acid, lamotrigine, carbamazepine, gabapentin) while others may worsen or induce depression, anxiety or behavioral issues (e.g., phenobarbital, phenytoin, levetiracetam, topiramate). Drugs that are used for treating depression and anxiety are also effective for these symptoms in people with epilepsy.
Psychotic reactions may occur during, after or between seizures. They may be associated with a large number of closely spaced seizures or, unexpectedly linked to a significant decrease in their number. People with epilepsy originating in the temporal lobe of the brain seem to be at higher risk.