Given the scientifically well-established connection between childhood attachment formation and certain aspects of an individual's later outcomes, to take this a step further, a causal connection was sought between childhood attachment formation and adult romantic relationships through a literature review. Further, by analyzing the applicability of the attachment theory and later romantic relationship outcomes across cultures, a connection between childhood attachment formation and adult romantic relationships across cultures was sought. Through an analysis of research published in peer-reviewed scientific journals in the recent decade, it was found that childhood attachment formation is predictive of later adult romantic relationships, and cross-cultural connections can also be made to an extent. However, it was also found that in many cases cross-cultural and even sub-cultural connections cannot always be made, and that there is a need for greater diversity in research going forwards. Connections between these findings were made with well-being in order to derive relevant application. Overall, a review of the literature supports that an adult's attachment style is related to his/her well-being. Further, subjective well-being is not always dependent on attachment security, although this is largely the case in the dominant western culture. In terms of well-being, when measured against certain other factors attachment security seems to have a weak effect across many cultures. This is interesting to consider in terms of implications for further study on cross-cultural determinants of well-being, in the context of attachment security, as the basis of most research on attachment security is for application in daily lives in order to achieve a higher level of well-being. In this context, then, it seems as though further cross-cultural research could assess attachment security in the context of culturally-relevant developmental well-being markers in order to compare and contrast universal determinants of well-being for a deeper understanding of the human experience.