What makes people grow? Love and hope.

Background: Hope and love are popular themes of literature and art in many human societies. The human physiology of love and hope is less well understood. This review presents evidence that the lack of love and/or hope delays growth disturbs development and maturation and even kills.

Main body: Love and hope intersect in promoting healthy human development. Love provides a sense of security and attachment, which are necessary for healthy physical, cognitive, and emotional development. Hope provides a sense of optimism and resilience in the face of adversity. Loving relationships can foster a sense of hope in individuals and in society by providing support systems during difficult times. Similarly, having a sense of hope can make it easier to form loving relationships by providing individuals with the confidence to connect with others. Hope and love are the fundamental basis of human biocultural reproduction, which is the human style of cooperation in the production, feeding, and care of offspring. Examples are given of the association between human growth in height with love and hope, including (1) the global "Long Depression" of 1873-1896, (2) "hospitalism" and the abuse/neglect of infants and children, (3) adoption, (4) international migration, (5) colonial conquest, and (6) social, economic, and political change in Japan between 1970 and 1990.

Conclusion: Overall, this review suggests that love and hope are both critical factors in promoting healthy human development and that they intersect in complex ways to support emotional well-being.