Why does hair suddenly fall out during periods of intense stress, and what is the effect of the hormone “cortisol” on hair follicles?

Under intense and chronic stress, the body releases high levels of the hormones “cortisol” and “adrenaline.” High cortisol levels reduce the synthesis of building blocks like hyaluronic acid and proteoglycans, which are located in the matrix surrounding hair follicles and are responsible for hair growth, by 40%. More importantly, cortisol prematurely and en masse pushes hair follicles from the growth (anagen) phase into the resting (telogen) phase. Approximately 2-3 months after the stressful event (the time hair remains in the telogen phase), these hairs begin to fall out in masses during showering and brushing. Clinical hair treatments counteract the destructive effects of cortisol during this process, forcing the follicles back into the anagen phase.