What is the significance of these findings? What are their wider implications? It is clear that smokers as a group do differ from nonsmokers as a group in a variety of characteristics. Yet, in no instance are these differential features found to be present exclusively in one group and completely absent in the other. There is no manifestation of a clear-cut smoker's personality. That this is so is not surprising. With about sixty million or more adults smoking in one form or another, it would strain credulity to expect that such a large segment of the total population, with its infinite varieties of temperament, would share in common a single personality type. Ultimately, the answer may lie in the existence of a number of more or less discrete types.
Whether or not there are smoker personality types, there may be important underlying processes which are in part responsible for the differences between smokers and nonsmokers. It is conceivable that such processes may play a role in determining whether a person becomes a smoker, and even the form of smoking adopted.
The eminent biometrician, Sir Ronald Fisher, reported on a study of the smoking habits of a series of male twins based on data gathered in Germany. His data showed about twice as many identical twins to be alike in their smoking habits as nonidentical twins—65 percent against 33 percent. In another group, of female twins from England, 83 percent of the identical pairs were alike in their smoking habits, as compared with 50 percent of the nonidentical pairs.
Further analysis of the female-twin data, in order to eliminate the possible mutual influence between twins living together, revealed greater concordance of smoking habits in identical twins brought up separately from shortly after birth than in nonidentical twins. Similar results were also obtained, independently, from data gathered in Scandinavia. This evidence suggests that there is a genetic factor in the formation of patterns of smoking behavior. In a study just completed but as yet unpublished, I investigated the relationship between characteristics of physical structure and the smoking habits of the members of the Harvard class of 1946; Certain aspects of this study are noteworthy. The class of college undergraduates examined anthropometrically was surveyed sixteen years later for its past and present smoking histories. The availability of anthropometric data at the college age gave the special advantage of representing the "pristine" physical status of the individuals, unaffected by habit, diet, physical activity, health, and disease of the subsequent adult years.
Moreover, the period covered by their smoking histories was closely related to the age span of maximum smoking experience. At the time of their reply to the smoking questionnaire, the Harvard alumni were thirteen years out of college and averaged thirty-five years of age. And the number of individuals composing the study—more than 900—was large enough to permit the breakdown of the smoker series into exclusive groupings of "pure" cigarette, "pure" cigar, and "pure" pipe smokers. All "mixed" smokers—those who regularly used more than one form of tobacco—were omitted from these classifications. Thus, many of the criticisms leveled against other studies were obviated in this investigation.
Briefly, this study revealed that substantial differences in body build exist between smokers and nonsmokers. Smokers are consistently larger than the nonsmokers. They are taller, heavier, broader in the shoulders and hips, bigger in the size of the chest, leg, and hand. But even more significant, there is a consistent graded arrangement of physical differentiation among the smoker types. The pure cigarette smokers are the least differentiated from the nonsmokers in physical structure, followed by the pure pipe smokers, while the pure cigar smokers differ most from the nonsmoker group. For example, in the case of body weight, the pure cigarette smokers are on the average more than four pounds heavier than the nonsmokers, the pure pipe smokers more than six pounds heavier, with the pure cigar smokers averaging an amazing ten pounds more in body weight than the abstainers. Similar patterns are observed for a number of other body measurements, all indicative of the same trends of deviation.
Despite the inherent limitations in the research done thus far, it has become increasingly clear that smoking, the form of smoking adopted, and abstention from smoking are structured reflections of very complex forces, innate and environmental, in constant counterplay. Rather than a superficial habit overlaid indiscriminately upon various persons, smoking appears to be a response to a wide variety of personality and behavioral characteristics which have their origin, in part, in the biological or genetic makeup of the individual.
This opens up important and far-reaching implications for the highly controversial subject of the association of smoking and lung cancer.
If smoking has a constitutional basis, then there is a possibility that persons of a certain makeup are peculiarly liable to both smoking and lung cancer, as well as other diseases. This is not as large a speculative step as appears on the surface. That there is a relationship between constitution and disease is generally accepted in medical circles. Such a relationship has been indicated for an extensive variety of diseases, including coronary artery disease, diabetes, arthritis, duodenal ulcer, rheumatic fever, tuberculosis, and hypertension. Even with respect to cancer, the evidence favors a biological substrate for cancer of the breast, cervix, and uterus, and it is not beyond the realm of possibility that a similar situation pertains to cancer of the lung.