Should we leave babies to cry?

One of the most popular fashions of the moment for training a baby to sleep is "controlled crying", where you leave your baby to cry for long periods with the hope that in the end they will stop crying and eventually learn to put themselves to sleep. Two things bother me about this concept. The first is I loathe the word "training" in the context of babies. Babies shouldn't be trained. Before being developmentally ready, a baby can't be trained. Once a baby is developmentally ready, he or she doesn't need training. The second is that I shrink from leaving a baby to cry for long periods. A mother's natural instincts tell her to go to her crying baby, so why has controlled crying become a strut of 21st-century child-rearing and where did it come from in the first place?

Bringing up babies is never separate from the prevailing mores of the time. Victorians wanted children who were seen and not heard and a child was brought up to be silent and barely visible. An equally cruel approach was proposed by Truby King in the 1920s. His aim was good, to encourage women to breastfeed. Everything else about his teaching is deeply upsetting and wrong. His key message is to feed your baby rigidly every four hours and never at night. Giving in to a baby, King proposed, would make him or her spoilt and weak. The exquisite irony is that King's rigid breastfeeding schedule is bad for breasts straining to produce enough milk to nourish a newborn baby. Every four hours during the day is not frequent enough to keep the milk flowing, so mums are driven to fall back on bottle-feeding. Could breastfeeding by the clock be responsible for the rise and rise of bottle-feeding?

Because his principles promised perfect babies, they were enthusiastically taken up by middle-class mothers. (In much the same way, controlled crying promises a contented baby, a claim which, not surprisingly, attracts adherents who want a quiet life, whatever it takes).

Thank goodness the gentle Dr Benjamin Spock came along in 1946 to relieve mothers of these cruel practices. He freed parents from King's heartless approach and encouraged mothers to rely on their own judgement about what their babies need, a philosophy I've long espoused. Now, we have robust science to back up the kindly Dr Spock and to seriously question the harshness of the controlled crying brigade.

It goes like this. Stress in infancy, caused by leaving a young baby to cry, is particularly painful because, if ignored, it results in high levels of stress hormones that dampen the formation of a healthy brain. A baby is born expecting to have stress managed for her – by her parents. The prefrontal cortex (the frontal lobes), the part of the brain that exerts control over emotions, is virtually non-existent at birth. Stress hormones will remain low if you or your partner or another caring adult teach your baby to trust by holding, stroking, feeding, nuzzling, reassuring, whispering and laughing. However, as her emotions are unstable, those stress hormones can shoot up if there's no caring adult alert to her emotional needs and prepared to calm her when she's upset.

To put it as bluntly as Sue Gerhardt in her marvellous book Why Love Matters, your baby can't "tune out" her stress hormones, she needs you to switch them off for her. The simple truth is that your baby doesn't have the equipment, anatomical or physiological, to deal with distress, because that part of the brain that would help her cope doesn't come on stream for another four to six months.

Your baby's whole system is moulded by how much early stress she has to contend with and how well you help her deal with it. I believe what a baby needs is the kind of parents who help her to recover her equilibrium. If you do this you'll be rewarded with a baby who learns to regulate her own stress hormones and her own emotions with them. On the other hand, if she's left to contend with stress and no-one helps her she'll push out stress hormones at the least thing. She'll be a baby who cries easily, remains upset despite comforting, and is inconsolable.

It follows that the best kind of mother is one who hugs her child when she feels the child needs a hug, who lifts her child when she thinks that her child wants to be picked up and who puts her down when she thinks her baby is ready for sleep. The same mother will feed her baby when he's hungry (and not clock watch) and let him sleep when she senses he's tired.

The admirable developmental psychologist Mary Ainsworth showed that every time you act on your natural instincts you're encouraging a happy and secure child. Every time you touch and caress your baby your touch activates growth hormones, which encourage healthy development.

Not the least of the baby's organs to be affected is your baby's brain. In their fine book A General Theory of Love, three American psychiatrists, professors Lewis, Amini and Lannon suggest that the bond of love or lack of it changes a baby's brain forever. This is because insecurity in early life leads to lifelong changes in a baby's brain chemistry. The levels of mood-lifting chemicals like serotonin and dopamine are lowered and blueprinted into a baby's brain in the first months of life. The professors believe with the wrong kind of mothering – letting a baby cry for long periods – this alteration of brain chemistry becomes hardwired, leading to timid, clingy children, neurotic, withdrawn teenagers and adults vulnerable to anxiety and depression.

Access to good experiences early on in life produces brains with more neural connections – more richly networked brains. With more connections there's better brain performance and more flexibility to use particular areas of the brain. Between six and 12 months, in the tender care of a loving parent, there's a massive growth spurt in these connections in your baby's brain, just the time when the pleasurable relationship with your baby is most intense.

When a baby feels pleasure, a chemical cascade of happiness flows through her. First a pleasure hormone called beta-endorphin is released into the circulation and specifically into the prefrontal region of the brain. These natural opioids help brain cells to grow by controlling glucose and insulin. They also make your baby feel good. At the same time another hormone, dopamine, is released from the prefrontal cortex. This, too, enhances the use of glucose, helping new brain cells to grow. If you want to know what this energising and stimulating effect feels like, just imagine being rewarded for a job well done. All those cuddles, gentle words and doting looks fire off the pleasure chemicals that help the social brain to grow. Which parent can resist that promise and not go to their crying baby?

Dr Miriam Stoppard is the author of 'Baby's First Skills', £8.99 and 'First-time Parents', £13.99, fully revised and updated, both published by Dorling Kindersley