Oh, it's called a Side Effect. I take a lot of medications and while they help me, some of them also do things besides what I take them for. A few of them make it hard to sleep. That's all. There's really no safe way for me to get around it so I deal with it alright, and make sure to sleep well when I can.

[He smiled reassuringly - he didn't want her worrying over it, after all.]