Didn't you say he was 13

A mother takes her son to a psychiatrist and says, "Doctor, I'd like you to evaluate my 13 year-old son."

"He's suffering from a transient psychosis with an intermittent rage disorder, punctuated by episodic radical mood swings, but his prognosis is good for full recovery."

"How can you say all that without even meeting him?"

"Didn't you say he was 13?"