Dear Dr. K: I had my first baby about a month ago, and ever since I have been feeling depressed and overwhelmed. I keep waiting for these feelings to go away, chalking them up to my adjustment to new parenthood, but they haven’t yet. At what point should I seek treatment?

Dear Reader: Most mothers experience the “baby blues” during the first few days after giving birth. Symptoms include anxiety, irritability and weepiness. They typically worsen by the fourth or fifth day after delivery. Then they go away over the next two weeks. The cause is unknown. It may be simply exhaustion from labor and delivery.

Postpartum depression is different. Compared to the “baby blues,” it is more severe, is constant throughout the day and also lasts longer. Since you’ve been feeling depressed for at least a month, I suspect you have postpartum depression. This condition can make you feel sad, worthless or guilty. You may find you’re unable to concentrate or take interest in anything, even your new baby.

We don’t know the causes of postpartum depression. Hormone fluctuations are one possibility. During pregnancy, your estrogen and progesterone levels rise dramatically. After delivery, those hormone levels plummet. These changes may lead to changes in your mood, sleep patterns, appetite and more.

It’s also possible that some women find the prospect of caring for a new baby very stressful. You might predict that this would be more likely to happen in women having their first baby. In fact, postpartum depression does appear to be more common after the first baby than after subsequent births.

Postpartum depression occurs in about five women out of every 100 who have a baby. It usually starts in the first two to three weeks after the birth of the baby. If you have had depression in the past, you may be more likely to suffer postpartum depression.

If you think you have postpartum depression, seek help. Lack of treatment can take a toll not only on your mental health, but also on the way your baby develops. Fortunately, there are many types of treatment for you to consider.