Personality factors in human drug self-administration.

By comparing MMPI profiles of sedative-dependent subjects during pentobarbital self-administration with comparable subjects during drug abstinence, the present study has found that self-administration tends to increase rather than decrease indicators of personal distress (MMPI scale scores). This finding agrees fully with other studies of drug effects on mood of drug-dependent subjects. (This finding should disturb only those who equate reinforcement with euphoria and other pleasurable states. Those familiar with the concept of reinforcement understand that reinforcement deals only with behavior and implies nothing about corresponding subjective states). Only scores on the Hypomania scale of the MMPI were found to correlate significantly with amount of daily drug intake, and this relationship occurred primarily in females. Scores on the Depression scale were correlated significantly with the daily pattern of drug-taking behavior. However, in neither case is it known whether the relationship reflects influences of personality factors on drug-taking behavior, or influences of drug-taking behavior on the obtained personality measures. Other research will be needed to answer this question. Clinically depressed individuals may constitute a special sub-group of subjects in which scores on many MMPI scales are related to daily amount of drug intake. Studies of human drug self-administration provide an excellent opportunity for more detailed research into these and other clinical research questions.