A longitudinal study in the 1970s tracked two groups of men over several years. Group 1 consisted of individuals described as highly competitive, impatient, and constantly working against deadlines. Group 2 consisted of individuals described as relaxed and easy-going. The study found that individuals in Group 1 were significantly more likely to develop heart disease by the end of the study period. Based on this evidence, what conclusion would have been most supported by the medical community at that time?