Not to add to the confusion, but since insomnia is a sleep disturbance (just like nightmares, frequent awakening, etc), it could be "ticked" under Psychiatric as well.
If you haven't already, you're now discovering that with Auditing E/M items mentioned/documented may fit into more than one category. Just as long as you're using it in one and only one you have no worries.
For instance, if you already have constitutional marked for "no wt. loss", then you could score "insomnia" under the Psych and move your ROS to Detailed.
Just a thought/clarification.