Personality and Smoking Patterns in a Twin Population

Summary The present study employed a sample of 76 sets of twins who were distributed over six groups classified by zygosity and smoking status to investigate personality variables relating to smoking behavior. Results based on an analysis of intraclass correlation coefficients and intra-pair differences on MMPI scales showed that while monozygotic twin pairs were more similar than same-sexed dizygotic twins, differences were generally unrelated to smoking behavior. A possible exception was the finding of a statistically significant relationship between smoking and scores of the Pd scale, but this finding was in direct contrast to results from previous research. The hypothesis that twin pairs discordant for smoking might also be less alike in personality than sets in which concordance for smoking behavior exists was not supported.