In recent years, empirical research has consistently supported an association between susceptibility to affective illness and creativity at the level of eminent achievement and at the non-eminent, or "everyday creativity" level. Although this research has provided greater evidence for the existence of this link, it has simultaneously unearthed more questions about how and why such an association exists. The purpose of this research was twofold: first, to provide further analysis of the nature of the relationship between hypomanic traits and creativity by employing a longitudinal study to determine the extent to which inter-individual differences over time in creativity are predicted by hypomanic traits. Second, the purpose of the cross-sectional analysis in the present study was to further determine how developmental components such as age and expertise may help unravel the ways in which hypomanic traits contribute to creativity and to further describe inter-individual differences among these variables. The first hypothesis, which proposed that the direction of the relationship between hypomanic traits and creativity could be predicted, was not supported by these results. The second research hypothesis was partially supported: hypomanic traits predict creativity in the combined adolescent and older adult samples. However, upon further examination of the regression analyses, the data indicate that the relationship between hypomanic traits and creativity is also influenced by age and developmental factors. Furthermore, the way in which the relationship is influenced by these other factors depends on the way in which the creativity construct is measured (e.g., process or personality. The findings suggest that the antecedents of creativity may differ between adolescents and older adults. In adolescents, the hypomanic traits measure is the only variable that predicts creative personality and creative process, while expertise is the only variable to predict creative personality and creative process among the older adults in this study. It appears expertise significantly and uniquely contributes to at least two areas of creativity in older adults, while hypomanic traits significantly and uniquely contributes to the same two areas of creativity in adolescents. Implications of these findings and limitations to this study are discussed.