NADD Bulletin Volume II Number 3 Article 1

Complete listing

The Relationship between Epilepsy and Violent Behavior in Persons with Mental Retardation

Jarrett Barnhill, MD


Aggression is a heterogeneous, multifaceted behavioral problem affecting up to 30% of individuals with severe/profound mental retardation (Parsons, May, Menolascino, 1984; Ratey and Dynek, 1996). These high rates of aggression incorporate a variety of different behaviors and are one of the principle reasons for psychiatric referral and the introduction of psychotropics. This paper will review one aspect of this problem, namely the relationship between epilepsy and violent behavior. Epilepsy and aggression frequently co-exist among persons with developmental disabilities, but the heterogeneity of both and the need for an independent analysis of each must temper a search for any common ground between the neurobehavioral symptoms.


Among persons with mental retardation, there is an inverse relationship between cognitive abilities and brain dysfunction. When compared to the general population, persons with mild mental retardation have slightly increased rates of epilepsy, static encephalopathy, or structural brain lesions. The clinical subtypes of epilepsy are also similar (Munro,1986). The vulnerability to aggression also approximates the general population. Aggressive behavior among higher functioning clients is associated with cognitive limitations, abuse/neglect, traumatic brain injury, clinical psychopathology, language disorders, substance abuse, and antisocial personality (Feinstein and Reiss, 1996; Roberts, 1986).

Among the severely/profoundly retarded, the prevalence of significant neurological disorders approaches 50% of the population. The seizure disorders are frequently characterized by focal or mixed seizure types; frequently require multiple anticonvulsants, and may remain refractory to aggressive medical treatment (Roberts, 1986). The accompanying brain dysfunction contributes to the significant cognitive and adaptive deficits associated with S/PMR. In this context, the rates of aggression increase with decreased behavioral flexibility, impaired adaptive skills, limited language or communicative skills, epilepsy, as well other brain disorders (Ratey and Dynek, 1996).

Aggressive behavior associated with neurological compromise tends to be impulsive, unplanned, explosive with a rapid intensification of irritability and is frequently disproportionate to the trigger stimulus (Burrowes, Hales, and Arrington, 1988). Although the outburst can be directed at selective individuals or property, the aggressive behavior may not appear instrumental, goal directed, or involve planning. This affective or reactive aggression is classified in the DSM-IV under Intermittent Explosive Disorder. Neurophysiologically, measures of autonomic arousal and sympathetic activation are characteristic of explosive aggression (Lewis, 1994; Pincus and Lewis 1991).

On the other hand, instrumental aggression, like predatory aggression, is usually goal directed, organized and planned by the perpetrator and is often successful in obtaining a desired end. In animal models, predatory aggression is directed at prey species and the goal is to injure or kill (Burrowes, Hales, and Arrington, 1988). In humans, this form of aggression can appear retaliatory, or used for interpersonal manipulation, intimidation, or coercion. The level of affective arousal is low and rage or irritability may not be present (Reid, 1988). Other forms of instrumental aggression may be highly ritualized and it appears that the client is communicating a need for space (territoriality) or recognition (dominance). This type of aggression may be displaced to property or posturing (verbal threats or warnings of impending aggression) and may be more common in stable living settings in which new staff or clients are introduced (Burrowes, Hales and Arrington, 1988).

Aggression can also be associated with primary psychiatric disorders such as schizophrenia, affective disorders (Goodwin and Jamison, 1990), anxiety disorders and dementia. In this context, aggression is a part of the psychiatric disorder- either based on psychotic symptoms or increased irritability (Junjinger, 1996,; Sovner and Fogelman, 1996). For these clients, the emergence of new aggression or elevations in baseline rates of well-established aggression may accompany symptoms of a psychiatric disorder. Unfortunately the diagnosis of primary psychiatric disorders in persons with severe/profound mental retardation is less reliable. When confronted with aggression, there is a significant probability that in addition to environmental or stress related changes in baseline aggression, a primary psychiatric disorder may be present based on the relatively high prevalence rates of these disorders in the population (Sovner and Fogelman, 1996).

For higher functioning clients, the availability of drugs of abuse may contribute to aggressive behavior in the community. The use of cocaine, alcohol and other “street” drugs may increase the frequency and severity of aggression by triggering psychiatric symptoms, decreasing compliance to the treatment plan, direct drug affects on a vulnerable brain, or during withdrawal (Junjinger, 1996). In each case, appropriate treatment of the primary psychiatric or substance abuse disorder will frequently lead to a marked reduction in this type of aggression. For other clients, precribed medication side effects may contribute to aggressive behaviors, especially akathisia, delirium, or disinhibition. Discontinuing or finding more appropriate treatment alternatives usually contains this type of aggression (Fava, 1997).


Epilepsy is a common problem among persons with severe/profound mental retardation, affecting nearly 50% of clients. Seizures can result from structural lesions (cerebral palsy, stroke, or tumor), metabolic abnormalities, endocrinopathies, or cryptogenic forms of epilepsy (Trimble, Ring et al ,1996). The latter may include complex mixtures of seizure types and require multiple anticonvulsants, dietary manipulation, or surgical correction. Even with these strategies, seizures were frequently uncontrollable, and probably contributed to further cognitive and adaptive deficits. Multiple anticonvulsants may have also compromised brain function- including increased irritability or behavioral disinhibition (Reynolds, 1985). The early age of onset, intractibility of seizures, compromised language function and vulnerability to overstimulation or cognitive overload may have contributed to the high rates of disruptive or aggressive behavior (Stagno, 1996; Lewis, 1994). Among higher functioning clients, documented physical /sexual abuse and neglect, brain trauma, language disorder, complex partial seizure disorder, social perceptual deficits and misreading of social cues as threats and periods of dissociation may contribute to violent behavior (Burrowes, et al 1988; Sovner and Fogelman, 1996, Stagno, 1996). These same factors may also contribute to aggression in the S/PMR, but adequate assessment is compromised by lack of language or communicative skills.

The localization of the seizure focus influences the rates of aggressive behavior. It appears that seizures that affect the anterior and mesial temporal lobes may increase the likelihood of aggression- especially if the amygdala/hippocampus and limbic system and associated hypothalamic circuitry are involved (Trimble etal, 1996; Neppe and Taylor, 1992). Electrical stimulation of these regions increases affective arousal and irritability as well as lowers the threshold for aggression in response to threat or conditioned stimuli (Adamic, 1983). Repeated seizures may kindle or sensitize these vulnerable structures, increase receptor binding sites and sensitivity to neurotransmitters such as glutamate, dopamine, or norepinephrine and down-regulate or reduce the number of GABA receptors (Perrine, 1991 Trimble et al, 1996). In addition, repeated seizures may initiate neuronal processes that contain the spread of the electrical impulse (Neppe, Tucker, 1992). This process may result in turning off significant frontal lobe structures that serve to regulate affect and behavioral response to environmental demands and social cues. This sort of disinhibition may also contribute to violent behavior in a variety of psychiatric disorders, based on a link between aggression, autonomic or sympathetic overactivation and diminished frontal lobe activity (Stagno, 1997).

Aggression may occur in the following states associated with a seizure disorder:

1.Prodromal irritability may precede the seizure by 24-48 hours. This sort of irritability may overlap premenstrual or luteal phase disorders, depressed mood, as well as lethargy or cognitive impairments (Neppe, et al, 1996; Blumer,1991; Cascino, 1992).

2.In spite of these alterations in brain functions, aggression during a seizure is probably exceedingly rare. During ictal outbursts, affective arousal/rage may be apparent, but behavior is poorly co-ordinated and highly stereotyped (Smith, Treman, and Trimble, 1991). Some frontal lobe seizures may be accompanied by complex patterns of movements, but these are usually brief episodes of poorly directed behaviors. Consciousness is usually preserved (Burrowes, Hales, and Arrington, 1988; Cascino,1992). The early phases of some complex partial seizures may involve fear or rage, especially those with a medial temporal onset and early involvement of the amygdala (Trimble, et al 1996; Mikati and Holmes, 1996). Spitting, snarling and growling may be present, but organized aggression is lacking. Post-ictal confusion, sleepiness, aphasia, or ““being out of it” is the rule and this state may last from minutes to hours (Fedio, 1986; Kortagal, 1996).

3. Post-ictal aggression is a presentation. As the seizure is ending, the person is in a delirious state and may readily misperceive or react in an explosive manner to attempts at protective restraint. The aggression can be directed, but the client may be amnesic for the event. Impairment in sensorium may be subtle, but confusion is usually present (Dodrill, 1992; Pincus and Lewis, 1991; Perrine, 1991). Other clients present with a period of normal function for up to 48 hours followed by the rapid onset of hallucinations, delusions, or active positive symptoms of psychosis (Trimble, 1991, 1996). During the psychotic phase, aggression may occur without confusion or disorientation and is frequently related to hallucinations, paranoid ideation, fear, or misperception of others (Neppe,Tucker 1992; Trimble, 1991). Most of these psychotic or affective changes are relatively short-lived and respond to protective environmental measures and short-term pharmacotherapy (Trimble, 1991; Stagno, 1997).

4.Interictal aggression occurs between seizures and may be associated with changes in the regulation of limbic activity (Benson, 1986, 1992; Fedio,1986). Some clients with CPS may experience increased irritability, moodiness, poor impulse control, and affective disregulation. Cognitive deficits and language impairments may also contribute to aggression (Brown, 1991). Aggression in this context may also include paranoid or referential ideation, irritability, mood disorders and psychoses. In higher functioning clients aggression may also be premeditated and have elements of instrumentality or predation (Pincus and Tucker, 1985; Trimble, et al, 1996). Diagnostically, these clients are categorized as Intermittent Explosive Disorder, Psychiatric Disorder due to a medical condition, or Personality Change due to seizure disorder (affectively labile and aggressive type) (DSM-IV). Better seizure control may not eliminate their neurobehavioral symptoms, so psychopharmacological strategies may be required (Fedio, 1986; Smith,Treiman, Trimble, 1991)


Violent behavior or extreme forms of aggressive behavior appear associated with intense autonomic/sympathetic arousal. These reactions represent an activation of the flight or fight mechanisms. Compromised frontal lobes, especially the right orbito-frontal cortex, reduce the top down regulation of this fear system(Junjinger, 1996; Pincus, 1990). Intense affective reactions may also occur in clients with lateral prefrontal brain damage, especially the left lateral prefrontal cortex (Borum, 1996, Burrowes, Hales, Arrington, 1988, Perrine,1991). Patients react with intense distress when confronted with unfamiliar or excessively difficult tasks. This neuropsychiatric connection with dysregulation of arousal is part and parcel of the problems encountered in clients with S/PMR. The presence of epilepsy adds periods of electrophysiological arousal, sensitization, or kindling of limbic structures (Trimble, Ring, and Scmitz, 1996). Most, patients with S/PMR and epilepsy, however, are not violent or extremely aggressive; the search for a common ground is elusive. Pincus and Lewis described a group of young murderers and noted that the presence of cognitive deficits, traumatic brain injury, electrophysiological abnormalities, and perceptual distortions were not enough to produce homicidal behavior. Dissociation and a history of abuse/neglect/or exposure to violence were needed to complete the picture (Pincus and Lewis, 1991).

Among persons with mental retardation, the presence of a seizure disorder is probably not sufficient to produce violent behavior. Many aggressive clients with mild/moderate MR share characteristics with those adolescents described by Lewis. This population may also be more vulnerable to drugs of addiction and this factor may have a significant impact on the rates of community based violence. Among persons with S/PMR, neurological may play a role, but abuse, or traumatization cannot be overlooked. Epilepsy may play a role and is but one factor in the equation of aggressive behavior. The treatment of aggression revolves around this principle as well as the fact that aggression occurs in a social context and must be understood in ecological terms.


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For further information contact:
Jarrett Barnhill, MD, Director,
Developmental Neuropharmacology Clinic
University of North Carolina School of Medicine
Chapel Hill, NC 27599-7160