I am sensory defensive. We are startled and bothered by all sorts of things: sound, smell, light. Our bodies are hypervigilent, which makes sleep difficult. The sheets, the light, the sound, the pajamas, everything has to be perfect. Yes, having another person nearby (as long as they aren't noisy or smelly, lol) makes us feel safer, which makes sleeping easier. I am surprised anybody can sleep alone. It is only in the last hundred years or so that sleeping alone wasn't an automatic death sentence. In some places we're still not the highest creature on the food chain. I can't sleep with my husband. He snores like a freight train. But I have 75 pound standard poodle, Rumsfeld, who sleeps right next to my bed. I sleep easier knowing if anything is out of place Rumsfeld's alarm will go off and he will protect me.