Al didn't know what else to do but he knew he couldn't remain outwardly emotionless, so he smiled. Smiling was safe to use in majority of situations.
"I did, to an extent. Her books helped me narrow it down to a set of symptoms to address. I did learn, however, that one shouldn't rely on a Muggle diagnosis."
His lips twisted into a smirk. "If you go by a Muggle book, Severus is permanently suffering from a postpartum depression."