A life cycle is a recurring pattern of stages that unfolds regularly throughout the lifespan of a living organism. In the context of humans, the human life cycle refers to the sequential progression of developmental stages from birth to death, encompassing the cycle of generations.

The human life cycle is often metaphorically likened to the seasons, with childhood and adolescence representing the spring of growth, adulthood symbolizing the summer of productivity, midlife (including menopause) reflecting the autumn of maturity, and old age signifying the winter of decline. This analogy gained widespread recognition following its introduction by psychoanalyst and developmental psychologist E. H. Erikson in the book “The Life Cycle, Its Completion.”

Erikson’s conceptualization of the human life cycle divides it into eight stages—infancy, early childhood, late infancy, childhood, adolescence, early adulthood, middle adulthood, and old age—focusing on the development of the human ego. Each stage is characterized by specific developmental tasks that individuals must address, with the tasks of one stage forming the foundation for the next, highlighting the psychological and social aspects of development.

Conversely, the terms “life course” and “life span” focus on individual life characteristics and the duration of life, respectively. Unlike the concept of the life cycle, they do not encompass generational aspects.

• Baba, R., & Nagai, R. (Eds.). (1997). Clinical psychology of life cycle. Baifukan.
• Erikson, E. H., & Erikson, J. M. (2001). The life cycle, its completion (Murase, T. & Kondo, K., Trans.; Expanded ed.). Misuzu Publishing.
• Tournier, P. (2007). The four seasons of life: Development and maturity (Miura, Y., Trans.). United Church of Christ in Japan Publishing Bureau.