Commentary: Alcoholic blackout--does it remove mens rea?

Disorders of impulse control are commonly induced by alcohol. As Lady Macbeth said, “That which hath made them drunk hath made me bold; What hath quenched them hath given me fire” (Ref. 1, p 1231). The report by van Oorsouw et al. from The Netherlands re-emphasizes the prevalence of alcohol-induced blackouts in a community sample and suggests that the claim of amnesia during a criminal event may serve a “strategic purpose” in court. This raises questions that are of importance to the legal system in general and to the forensic psychiatrist in particular. Blackouts “consist of a dense amnesia for significant events which have occurred during a drinking episode, which at the time outward behaviour perhaps seemed little disordered” (Ref. 3, p 595). Although alcohol has been consumed for the duration of recorded history, and probably before, remarkably divergent opinions about drinking behavior are held by scientists and lay persons, perhaps reflecting positions that are more philosophical or religious than empirical. The tools of epidemiology, as used by van Oorsouw et al., are powerful aids in the validation of syndromes and provide clues to the etiology of disease. Recent research has demonstrated the varieties of genetic transmission of alcohol abuse and has helped to elucidate genetic/environmental interactions in the etiology of this major public health and social problem. Previous epidemiological surveys have reported that of college students who drink, more than 50 percent have experienced a blackout at some point in their lives. Criminal or dangerous behavior is not unusual during a blackout. In their sample, van Oorsouw et al. found that 85 percent of blackout-claiming individuals had had a road accident, and White et al. found that 37.5 percent of their male sample had had fights, 25 percent had damaged or vandalized property, and 25 percent had had intercourse with someone they did not know. Blackouts during alcohol intake are phenomena similar to episodes of “transient global amnesia,” a neurological syndrome that closely resembles a blackout, except that it occurs in the absence of alcohol, perhaps because of basilar cerebrovascular insufficiency (or during a migraine-equivalent episode). These episodes are not accompanied by drowsiness, inattentiveness, or impairment of consciousness, and speech and behavior may appear normal to an outside observer. White has described the mechanism for alcoholic blackouts as involving disruption of activity in the hippocampus. Ethanol inhibits NMDA (N-methyl-D-aspartate type of glutamate receptor), a receptor involved in synaptic plasticity and longterm potentiation (LTP). The differential diagnosis of the cause of amnesic episodes includes complex partial seizures, hypoglycemia, transient ischemic attacks, concussions and head injury, intoxication with sedatives, Korsakoff’s syndrome, or encephalitis. Psychogenic amnesia may also be considered, but there is usually an emotional precipitant. These victims do not even remember their own names, and they may have amnesic periods lasting days or weeks. The memory deficit of alcohol-induced Wernicke-Korsakoff syndrome, actually two different disorders, consists of a “global confusional state” in Wernicke syndrome, versus the purely anterograde and inconsistent retrograde memory disorder of Korsakoff syndrome, which does not include a confused state. Confabulation is a striking, but inconsistent, Dr. Merikangas is Clinical Professor of Psychiatry and Behavioral Neuroscience, George Washington University, Washington, D.C. Address for correspondence: James Merikangas, 4938 Hampden Lane, No. 428, Bethesda, MD 20814. E-mail: [email protected]