It's likely caused by drug abuse, but it could be post-partum psychosis. My wife had it and it's unbelievable. I was often terrified of coming home to a murder-suicide situation. It's better now, but post-partum depression and the rarer post-partum psychosis are real isssues.
Apparently so.
I'm glad your wife is better now, but it must have been an awful time for you both.