Abstract
This paper looks at the concept of constitutional type and reviews a number of classification systems used by twentieth-century researchers and clinicians. In particular, it examines those very slim individuals characterized by W. H. Sheldon as ectomorphs. The paper contends that such individuals have, by virtue of their body build, the tendency to a catabolic-anabolic balance. This tendency is exacerbated by stress to which such individuals may be especially prone. Mutually reinforcing states of hyperarousal and hypermetabolism eventually result in states of fatigue, depression and the breakdown of immune and hormonal systems. This model has implications for treatment.