There’s a laundry list of things that can cause hair thinning. Stress, nutrient deficiencies, aging, and even the way you style your strands are only a few of the most common culprits behind hair loss. And while you’ll want to work with a board-certified dermatologist to figure out (and address) the root of the issue, the easiest ways to fake the appearance of fuller hair at home is with one of the best conditioners for thinning hair.