Thrips can hurt the plant's natural growth and development processes but rarely kill cannabis plants. The leaves they attack will shrivel and might eventually fall off, but a thrips invasion is never a fatal attack. However, thrips open the plant tissues for fungal and bacterial infections, so the risk must be averted by addressing thrips as soon as you notice they exist.  Cannabis plants mostly survive a thrips invasion, but the quality and size of your yield will be inferior when you harvest from sickly plants.