Alterations in thinking, delusions, or hallucinations, push the diagnosis of depression, categorically, into psychosis. After delivery, postpartum depression is a serious illness to be distinguished from the "postpartum blues." Thought disorders can get fairly creepy when the mother starts having threatening thoughts about her baby. But this woman isn't any more afflicted after birth than she would be at any other time if she has a history of mood disorders.
According to the American College of Obstetricians and Gynecologists, Technical Bulletin 182, "Depression in Women,"
"Major clinical depression has been thought to be more common following childbirth than during other periods of a woman's life. However, current studies do not substantiate this belief. Women at risk for significant postpartum depression are more likely to have a family history of depression, a previous postpartum depression, or significant adjustment problems with childbirth. It has been demonstrated that women who have a planned pregnancy in a secure environment, enjoy a supportive relationship with their partner, and have manageable levels of life stress are less likely to experience postpartum depression."
Clinically diagnosed depression is a psychiatric emergency, because a woman is in a very difficult period of adjustment and less likely to climb out of her despair, hopelessness, and suffering. She poses a danger to herself, her new baby, and to her marriage. Often a new father, learning to deal with the issues of this new world order, can't understand why such a wonderful time is being ruined by a bad mood, an attitude, or misdirected anger. Obstetricians, nurses, social workers, midwives, doulas, and even lactation nurses can be a crucial help in recognizing depression. They can counsel the husband on the pathology involved, and explain how this illness needs as much patience and convalescence as any physical illness.
During pregnancy real depression is a high-risk situation, which tends to make patients prone to non-compliance with their prenatal care (i.e. keeping appointments, eating right, doing what's best for the baby). Substance abuse, either prompting the depression or because of it, doesn't mix well with a developing baby either. And, prescribing legitimate anti-depressant drugs is also a concern, but is weighed as a risk vs. benefit decision. In true depression, the benefit usually far outweighs any potential risks.