Why are disorders of thinking or behavior so common in epilepsy?

A model for understanding the relationship

Many people with epilepsy lead happy and fulfilling lives. Nevertheless, formal research has shown higher rates of mental and behavioral disorders (also known as psychopathology) among those with epilepsy than among the general population. For centuries, superstition and unproven theories provided the only answers to the question, "Why does this occur?" In the 1980s, researchers Bruce P. Hermann and Steven Whitman looked at what had been written about this issue and developed a conceptual model of the phenomenon, describing what was known and pointing toward promising directions for further study. They were the first to recognize the complexity of the issue and to state explicitly many of the factors that are likely to be involved. They enabled those studying the behavioral effects of epilepsy to leave behind many misconceptions from the past and enter the modern scientific age. Their approach has been responsible for many studies continuing to this day.

Their model proposes that neurological, psychosocial, and treatment-related factors in epilepsy work together to exert a negative influence on behavior:

Neurological Factors

Hermann and Whitman proposed that a number of brain-related factors associated with epilepsy can affect a person's behavioral functioning. Some of these-brain tumor, stroke, or head injury, for example-may be the direct cause of the epilepsy. In other cases, the problem may be more subtle. For instance, hippocampal sclerosis (cell loss and scarring in the hippocampus, a very small structure located in the inner surface of the brain's temporal lobe) is characteristic of some types of epilepsy and may be just as likely as a more obvious disorder to affect behavior, even if the individual never experiences a seizure.

Hermann and Whitman's model also accounts for the direct effects of the epilepsy. Many features of seizures, including their type, number, and the patient's age when they began, are important factors. So are characteristics of the underlying EEG abnormalities, including how localized or diffuse they might be.

When the effects of the underlying brain disorder are combined with the effects of continuing seizures, the result can be an underlying brain state that makes the person with epilepsy susceptible to developing many forms of psychopathology, such as mood disturbance or psychosis.

Psychosocial Factors

A number of non-brain factors are considered to be equally important causes of behavior change. Epilepsy is a chronic condition that can be just as disruptive to a person's life as any other long-term medical illness. Ongoing seizures can interfere with simple leisure activities and can be significant obstacles to working or going to school. The pressures resulting from being unable to fulfill various roles, both in the family and in society at large, can lead to feelings of hopelessness and decreased self-esteem. Problems can be worsened by society's continued misconceptions about epilepsy. The person can thus develop psychopathology in reaction to having epilepsy and experiencing the limitations it imposes.

Treatment-related Factors

There are many effective treatments for epilepsy, but most of them are associated with some side effects. The most common treatment, medication, often causes various cognitive side effects. These sometimes may underlie psychopathology. Medications also can affect hormones and other neurochemical processes that can provide the substrate for developing conditions such as depression or anxiety.

Hermann and Whitman originally focused on the effects of medication, but there now is clear evidence that other forms of epilepsy treatment, including surgery, can also make patients more susceptible to behavioral disturbance.

Reference

Hermann BP, Whitman S. Behavioral and personality correlates of epilepsy: a review, methodological critique, and conceptual model. Psychological Bulletin 1984 May;95(3):451-497. PMID: 6399754.

Look for more information at PubMed, a service of the National Library of Medicine, at www.ncbi.nlm.nih.gov/pubmed/

Abstracts (summaries) of many articles related to this topic can be found by typing epilepsy or seizures into the PubMed query box, followed by AND [uppercase] and another term such as depression, stigma, psychosis, or "affective disorders". If you're looking for a special topic, review the Tutorial on search strategies.