The Primary Care Companion to the journal of clinical pscyhiatry has a good article called Billing for the Evaluation and Treatment of Adult Depression byt the Primary Care Clinician. (pdf)
It's a good overview of a challenging topic. It's well documented that primary care physicians are poorly reimbursed. It's hard to be appropriately reimbursed for our time - which of course is are most valuable commodity. Funy that I can remove a toenail in 10 minutes and earn several times what I can earn to listen to someone for 45.