It is important for the family members to recognize any symptoms of feeling low and depressed and then report to the doctor immediately.
Certain investigations e.g. Thyroid levels can be done as hypothyroidism can trigger depression.
Counseling sessions with an expert, understanding caring near and dear ones and anti-depressants can effectively help in managing the situation. A consultation with a psychiatrist may at times be required. The medications have to be taken judiciously as there are benefits for the mother, but they pass through the breast milk and therefore have risks for the baby.