How long does hair normally take to grow back in a healthy person with no hereditary hair loss?

For example, if hair follicles fall out (or gets yanked out from aggressive brushing), how long does it usually take to start growing? I have had long hair, bleached it, and since it became dry, I started brushing more aggressively and noticed a lot of hair on my brush and thinning at the top. Could this have triggered androgenic alopecia or will it grow back? I know I have to see a real doctor, but I feel many clinics are trying to sell me one of their treatment plans. Would like some advice please.