WIKLER'S PHARMACOLOGIC THEORY OF DRUG ADDICTION

Abraham Wikler (died 1981) was one of the first researchers who, in the late 1940s, strongly advocated the idea that drug abuse and relapse following treatment are influenced by basic learning processes. Early in his career, Wikler became interested in reports from relapsed heroin addicts that despite being free of withdrawal symptoms during treatment and upon discharge, they experienced withdrawal symptoms and craving when they returned to their drug-use environments—and that these feelings were responsible for their return to drug use.

Based on these and other anecdotes, Wikler—who was familiar with the recent work of Russian physiologist Ivan Petrovich Parlor (1849-1936) on conditioning—proposed that events which reliably signal drug self-administration or drug withdrawal elicit conditioned responses (CRs) that take the form of withdrawal and drug craving. According to Wikler, these CRs motivate further drug use, which, by terminating negative withdrawal feelings, perpetuates the cycle of drug dependency.

At the heart of Wikler's model lies the notion that classical conditioning mechanisms are activated when events surrounding drug use reliably begin to signal upcoming drug administration. These events may be external cues (e.g., the sight of a syringe) or internal states (e.g., depression) that consistently precede drug use. In nondependent users (who take drugs infrequently), Wikler proposed that the unconditioned response (UR) elicited by the drug consists of direct effects of that drug on the nervous sytem. In such individuals, stimuli that signal drug use would then come to evoke druglike responses; however, a different set of CRs are thought to occur in long-term drug users who have become physically dependent on the drug. These individuals experience withdrawal symptoms as the drug effect wanes and consequently, stimuli associated with drug withdrawal in these individuals evoke withdrawal reactions.

The aversive symptoms produced by withdrawal in dependent users provide motivation to self-administer the drug. Through a process of operant conditioning, drug taking is rewarded by the termination of the negative withdrawal symptoms. These reward experiences further strengthen the tendency of the drug user to turn to drug use when experiencing withdrawal symptoms. Likewise, stimuli paired temporally with withdrawal may also acquire the ability to elicit drug taking. Because Wikler invoked both classical and operant conditioning mechanisms as contributors to drug use, his model has often been characterized as a two-process model of drug use.

Wikler's model also provides for a powerful account of relapse following treatment for drug use. Because some treatment programs separate the abuser from the drug-use environment, the patient never learns to deal with drug-related events. Upon returning home following treatment, even though no longer physically dependent, the patient encounters drug signals, experiences conditioned withdrawal reactions, and eventually turns to drug use to reduce the negative feelings. Since conditioned responses show little spontaneous decay over time, the drug-use patient is at risk even following an extended treatment program. According to Wikler, treatment programs need to address conditioned responses directly. One suggested approach involves having subjects go through their usual drug-preparation ritual in a protected setting, where drugs are not available. Such exposures should serve to extinguish drug-use responses by failing to reinforce them with relief from withdrawal. Extinction training as well as other techniques for reducing the role of conditioned responses in relapse are currently being explored.

(See also: Behavioral Tolerance ; Causes of Substance Absue: Learning ; Naltrexone ; Research, Animal Model: Learning, Conditioning and Drug Effects )

BIBLIOGRAPHY

Wikler, A. (1977). The search for the psyche in drug dependence. Journal of Nervous and Mental Disease, 165, 29-40.

Wikler, A. (1973). Dynamics of drug dependence: Implications of a conditioning theory for research and treatment. Archives of General Psychiatry, 28, 611-616.

Wikler, A. (1965). Conditioning factors in opiate addiction and relapse. In D. I. Wilner & G. G. Kassenbaum (Eds). Narcotics. New York: McGraw-Hill.

Wikler, A. (1948). Recent progress in research on the neurophysiologic basis of morphine addiction. American Journal of Psychiatry, 105, 329-338.

Steven J. Robbins