Like ecological economics it focuses on measuring well-being and detecting uneconomic growth that comes at the expense of human health. However, it goes further in seeking not only to measure but to optimize well-being by some explicit modelling of how social capital and instructional capital can be deployed to optimize the overall value of human capital in an economy - which is itself part of an ecology. The role of individual capital within that ecology, and the adaptation of the individual to live well within it, is a major focus of these theories.
The most notable proponent of human development theory is Amartya Sen, who asked, in Development as Freedom, "what is the relationship between our wealth and our ability to live as we would like?"
This question cannot be answered strictly from an energy, feminist, family, environmental health, peace, social justice, or ecological well-being point of view, although all of these may be factors in our happiness, and if tolerances of any of these are violated seriously, it would seem impossible to be happy at all.
Accordingly, human development theory is a major synthesis that is probably not confined within the bounds of conventional economics or political science, nor even the political economy that relates the two. It may also be over-ambitious, as objective measures of relative happiness and marginal utility in the pursuit of happiness do not seem readily accessible to economics.
See also: ecological economics, welfare economics