How Postnatal depression can affect children and their families

What happens to the relationship a mother can form with her baby when she is postnatally depressed? What are the longer term implications for the child's development? I will consider this, not just in one direction of effect from a mother to the child. Babies come in different shapes, sizes and temperaments and what your baby is like is going to have a big impact on what kind of care you will find yourself able to give.

First of all let us think about what we know about the effects of depression on social responsiveness.

So many facets of our communication change when someone is depressed:

• intonation of the voice
• the pitch of the voice
• the speed with which we speak
• the eye contact we can make
• our responsiveness.

Babies are highly sensitive to all these parameters of communication right from the beginning.

Research that has been done on infant development in the last 30 years shows that even infants of between four and twelve weeks old engage in complex communication with the people who are looking after them. By a few weeks the baby is able to gaze reliably at another person, smile and vocalise. They have a rich range of expressions and gestures and can take a really active part in communication. In turn the parents, not just mothers, and other children, unconsciously adapt to the nature of the infant's needs and communication. They will adopt a particular characteristic style of responding: pitch changes, it tends to go up; speed goes down; and the intonation contours get exaggerated.

The communication tends to operate on mimicry, so the partner will pick up on the baby's cues and typically respond back by mirroring them or elaborating a little bit on what the baby has done.

The interactions between parent and baby look like a two-way conversation, although at this time they tend to have little reference to the outside world. At this stage the baby cannot reach out and grab things, they are not able to move around on their own and their eyesight is not that good. The conversations that happen in the first three months tend to be in this arena of face-to-face contact they are purely about the communication itself.

What we do know about babies is that they are highly sensitive. If the quality of communication changes, as it often does in people who are depressed, then the sensitivity of the baby potentially takes on an important clinical significance. What is the effect for the baby whose primary environment, for many hours of the day, is constituted by this one person who may be depressed? Let us look at the research evidence in general and then describe some of it in more detail.

Studies that have looked at infants of mothers who have had postnatal depression have found that:

• babies score more poorly on the Bayley scales, the general measure of infant mental development
• they score worse on Piaget's Object-Concept tasks
• in our study, the boys of mothers who have been postnatally depressed scored particularly badly in these tests.