The symptoms

A form of severe depression (ie severe anxiety that is totally out of proportion, doesn't respond to objective reason, has no apparent cause, and won't go away).

Loss of interest and pleasure in daily activities (you don’t want to do anything: go out, look after the baby, do things with your partner).

Loss of appetite and rapid weight loss, or bulimic episodes.

Severe loss of sleep (other than loss of sleep caused by the baby waking): insomnia, waking suddenly, disturbed sleep.

Physcial restlessness, yet mental sluggishness. 

Extreme fatigue, loss of energy, feelings of worthlessness and/or guilt. Loss of concentration, incapability to make even the most simple decisions.

Frequent thoughts of death and suicide. In the severest cases, hallucinations can occur.