Plasma endorphin levels in pathological gambling

Abstract

Despite its formal definition as a disorder of impulse control, pathological gambling has come under the generic label of addictive disorders with subjective excitement and physiological arousal as the major motivating factor. Individual differences in autonomic/cortical arousability in interaction with irregular schedules of reinforcement have been postulated to be important determinant factors in the pathogenesis of pathological gambling (Anderson & Brown, 1984). Mood disturbances and cross-addictions are frequently observed in pathological gamblers seeking treatment and the behavior has also been conceptualized as a defense against depression and anxiety. Recently the role of endorphins has been implicated in mood disturbances associated with psychiatric states and in addictive processes; the latter through their euphorogenic or reward-transmitting properties in accordance with operant and classical conditioning principles. The hypothesis that the etiology or maintenance of gambling behavior is related to endorphin activity was investigated in this study. Using radioimmunoassay techniques, baseline B-endorphin plasma levels were measured in a sample of 39 pathological gamblers seeking treatment and 16 male and 19 female non-gambling healthy control subjects. In addition, B-endorphin reactivity to gambling activity was measured in a subgroup of 13 horse-race gamblers. Diagnostic and Statistical Manual III criteria for diagnosis were used. Written consent was obtained. Blood samples were drawn at the same time of day for each subject. The experimental procedure consisted of taking baseline blood samples at 11 a.m. following which subjects were instructed to place a bet sufficient to “excite” them on a horse-race. A subsequent blood sample was taken at 2 p.m., five minutes after subjects listened to the race broadcast on radio. Heart rate measures and a visual analogue scale rating excitement, tension and urge to gamble were also administered immediately before and after the race broadcast. Results showed that as a group pathological gamblers did not differ from controls on baseline B-endorphin levels. But differentiating gamblers according to type of gambling activity revealed horserace addicts to have significantly lower baseline levels as compared to poker-machine players and controls. This finding provides empirical evidence for the hypothesis that distinct subgroups of gamblers exist and raises the corollary that different etiological factors may characterize each subgroup. That B-endorphin levels did not increase in response to gambling was explained by the failure of the relatively small bet size to generate high arousal.