Trauma can cause hair loss.

This is true. Physical or emotional stress can cause hair to fall out, even a few months after the event. A death, divorce, or even childbirth can cause individual hair follicle cycles to sync, meaning that instead of hair falling out at a rate of 100 follicles per day, large amounts can come out at the same time. Follicle cycles commonly sync after chemotherapy and rapid shifts in weight. Hair loss as a result of cycle syncing should grow back eventually and does not require a transplant. A non-surgical option might make you more comfortable or speed up the regrowth process.