One-in-five mothers experience the "baby blues" - known clinically as post-natal depression. In too many cases, they soldier on without support, often afraid to admit how bad they are feeling. After all, when that much-desired baby finally arrives - often after many years of planning - shouldn't the new mother feel ecstatic? Not necessarily, especially when the exhaustion of sleepless nights and the stress of combining work outside the home with babycare come into play.

New research shows that mother may not be the only person in the house to feel depressed. At Emory University in the US researchers found that babies and depressed mothers were suffering from the same chemical imbalance.

A large percentage of the babies of depressed mothers had the same high blood level of a hormone that indicates high stress levels - cortisol. Why is this? The suggestion is that a depressed mother may either ignore her child, or else overwhelm her baby with attention. Both extremes of mothering behaviour can cause the baby to become stressed. Researchers found that mothers who underwent treatment for the imbalance were quickly returned to their normal blood level, while their children, who were left untreated, still maintained a higher level of stress-causing cortisol.

Moral of the story: if you are a new mother and feel down, get help from your GP as soon as possible. Fathers and other carers should keep an eye on the new mother and make sure she gets help, even if she doesn't see the need herself.