Stress can cause hair loss is some people. Usually it occurs 3 months after the stressful event has occured and it may take 3 months after the stress period has ended for the hair growth to resume. In most cases it is temporary if the person is not predisposed to genetic or Androgenic Alopecia, if they are stress may trigger the onset of genetic hair loss or may worsen existing Androgenic hair loss.MECHANICAL DAMAGE CAUSES HAIR LOSS Damage to the hair can be self inflicted either by intentional or unintentional means. Some people going through stress continuously pull at their hair until it comes out. Styling hair by bleaching, braiding and straightening can also cause damage and results in hair being lost.Trichotillomania or Hair PullingSome children and less often adults play with their hair by pulling on it or twisting it. This can be part of a behavioral problem or a bad habit that is often done unconsciously. If the behavior is not stopped permanent hair loss can result from the constant stress on the hair. Its best to seek the help of a mental health professional to solve this problem.  Many people change the appearance of their hair by using chemical treatments like dyes, tints, bleaches, straighteners, relaxers and permanent waves. If correctly done and done using reputable products, its rare to have any damage. However, hair can become weak and break if any of these chemicals are used too often. Hair can also break if the solution is left on too long, if two procedures are done on the same day, or if bleach is applied to previously bleached hair. Some chemical relaxers do contain powerful chemicals and there have been instances of people get chemical burns from these products resulting in permanent hair loss. Only go to qualified hair stylists and if doing it yourself make sure you only use reputable products and follow the product directions.Hair Braids/WeavesMany black women and some black men braid their hair or wear hair weaves. Under normal conditions these cause no problems. However if the weave is attached too tight or the braids are wrapped too tight, they put a constant strain on the hair follicle. If this is done for an extended period of time permanent hair loss can result. This is known as Traction Alopecia and is fairly common among people who braid or weave their hair. Make sure the person applying the braids or weave is qualified to do so and don't wear braids or weaves continuously for extended periods of time.