Causes of hair loss: from genetics to stress
About 25% of men begin to bald by the time they are 30 years old, and about two-thirds are either bald or have a balding pattern by age 60. 
The average scalp contains about 100,000 hairs (blondes 140,000, brunettes 155,000 and redheads only 85,000). On average, about 100 hairs are lost from the head every day.
Each individual hair survives for an average of 4.5 years, during which time it grows about half an inch a month. Usually in its 5th year, the hair falls out and is replaced within 6 months by a new one.
Three causes of hair loss
Baldness, or androgenic alopecia, is most often caused by three determining factors:
- Genes. Genes are believed to influence hair loss. Unlike what is popularly believed, hair loss is not solely inherited from the mother's side of the family. It can be inherited from either the mother or father. It is important to note, however, that the genes responsible for male pattern baldness have yet to be identified.
- Hormones. Hormones may play a role in hair loss. Hormones are biochemical substances produced by various glands throughout the body. In men, the presence of such hormones as androgens, testosterone, and DHT cause some hair follicles to regress and die.
- Stress. Stress induced by traumatic experience, nutritional deficiency, or illness can cause the rate of hair loss to increase. The regular, day-to-day stresses of life do not cause hair loss.
