I'm sure it's true, but I don't know whether it's the actual sleep itself that's different while stressed, or just our increased preoccupation while awake making us lack focus on our dreams. While stressed, like the last few days, I've definitely remembered fewer dreams, but that might have been because I was focusing so much on the essay due I didn't have as much time to get excited about dreaming and therefore had no lucid dreams or memorable dreams.