The human body contains many natural polymers, such as proteins and nucleic acids. Cellulose, another natural polymer, is the main structural component of plants. Most natural polymers are condensation polymers, and in their formation from monomers water is a by-product.
Alopecia areata is one type of hair loss that typically causes patches of baldness. In some cases, total baldness develops. In many cases, the hair re-grows, typically after several months. In some cases, the hair loss is permanent.
Depression does not cause hair loss, and hair loss does not cause depression - as far as we know. There are more than 30 different medical conditions that contribute to hair loss in women. Hormones, diet, childbirth, illness, birth control pills, poor diet, stress - all have been found to contribute to thinning of hair in women.