Infant sleep training

Infant sleep training refers to a number of different regimens parents employ to adjust their child's sleep behaviors.

The development of sleep over the first year
During the first year of life, infants spend most of their time in the sleeping state. Assessment of sleep during infancy presents an opportunity to study the impact of sleep on the maturation of the central nervous system (CNS), overall functioning, and future cognitive, psychomotor, and temperament development. Sleep is essential to human life and involves both physiologic and behavioral processes. During the first year of life, infants spend most of their time in the sleeping state. Sleep not simply as a resting state, but a state that involves intense brain activity. The first year of life is a time of substantial change in the development of both the human brain and sleep. The relationship between the two is vital, as the control of sleep and the sleep-wake cycle are regulated by the CNS.

The long sustained sleep period (LSP) is the period of time that a child sleeps without awaking. The length of this period increases dramatically between the first and second months. Between the ages of three and twenty-one months, LSP plateaus, increasing on average only about 30 minutes. In contrast, a child’s longest self-regulated sleep period (LSRSP) is the period of time where a child, without sleep problems, is able to self-initiate sleep without parental intervention upon waking. This self-regulation, also called ‘’’self-soothing’’’, allows the child to consistently use these skills during the nocturnal period. LSRSP dramatically increases in length over the first 4 months, plateaus, and then steadily increases at 9 months. By about 6 months, most infants can sleep 8 hours or more at night uninterrupted or without parental intervention upon awaking.

In terms of actual numbers, an infant from one to three months of age may sleep sixteen to eighteen hours a day in periods that last from three to four hours. By three months the period of sleep lengthens to about four or five hours, with a decrease in the total sleep time to about fourteen or fifteen hours. At three months, they also start to sleep when it is dark and wake when it is light. By 4 months there are 2 distinct napping periods, mid-morning and late afternoon. By 6 months the longest LSP is 6 hours and occurs during the night. There are two 3-or-more hour naps with a total average sleep time of fourteen hours.

Though sleep is a primarily biological process, it can be treated as a behavior. This means that it can be altered and managed through practice and can be learned by the child. Healthy sleep habits can be established during the first four months to lay a foundation for healthy sleep. These habits typically include sleeping in a crib (instead of a car seat, stroller, or swing), being put down to sleep drowsy but awake, and avoiding negative sleep associations, such as nursing to sleep or using a pacifier to fall asleep, which may be hard to break in the future.

Every child is different and each child’s sleep becomes regular at different ages within a particular range. In the first few months of life, each time the baby is laid down for bed and each time he or she awakens is an opportunity for the infant to learn sleep self-initiation and to fall asleep without excessive external help from their caregiver. Experts say that the ideal bedtime for an infant falls between 6 pm and 8 pm, with the ideal wake-up time falling between 6 am and 7 am. At four months of age, infants typically take hour naps two to three times a day, with the third nap dropped by about 9 months. By 1 year of age, the amount of sleep that most infants get nightly approximates to that of adults.

Good Sleep Conditions
Many parents try to understand, once the baby is asleep, how to keep them sleeping through the night. It is important to have structure in the way a child is put to sleep so that they can establish good sleeping patterns. Researchers have found that babies learn how to fall asleep through a process called operant conditioning, by use of reinforcement. Sleep will reinforce the behaviors that precede it. Regular cues including those mentioned above, such as dimming the lights, singing lullabies, quieting the surrounding environment right before bed or the association of a fixed and specific place for sleep, act as stimuli for the behavior of ‘’self-sustaining sleep’’; that is, sleep that will be triggered by the child him or herself and last through the night. There are additional hypotheses as to what might help and hurt a child in falling asleep and staying asleep. Some researchers believe children who learn to fall asleep on their own have longer sleep cycles as opposed to falling asleep with parental presence. As well, comforting children, upon awakening, outside of their beds is associated with poor sleep consolidation. Comforting should take place within the child’s bed area. Parental attention will however act as reinforcement for signaling or calling out to the caregiver if intervention is too long or busy (such as feeding). Attending to the infant upon being signaled should be as short as possible, if the goal is to train the child to put him/herself back to sleep if s/he wakes up in the night. When the caregiver provides intense intervention, the infants’ crying is “rewarded” by the comfort of a parent. The child will deduce that if s/he cries, the parent will provide excessive attention.

Other influences on infant sleep
A number of factors have been shown to be associated with problems in sleep consolidation, including a child’s temperament, the degree to which s/he is breast-fed vs. bottle-fed, and his/her activities and sleepiness during the day. Moreover, co-sleeping, which is defined here as sharing a room or bed with parents or siblings in response to an awakening, can be detrimental to sleep consolidation. It is important to note that none of these factors have been directly shown to cause children’s sleep consolidation issues. In terms of infant feeding, breastfeeding has been found to be associated with more waking at night than bottle-fed infants because of the infant’s ability to digest breast milk more quickly than formula. Thus, breast-fed infants have been observed to begin sleeping through the night at a later age than bottle-fed infants: bottle fed infants tend to begin sleeping through the night between 6–8 weeks, while breastfed infants make take until 17 weeks before sleeping through the night. Seventeen weeks of age is still within the first 4–5 months of the infants’ life; therefore, this cannot really be considered a delay in sleep consolidation. There are many benefits to breastfeeding infants, Lastly, temperament also seems to yield correlations with sleep patterns. Researchers believe that infants classified as “difficult,” as well as those who are very sensitive to changes in the environment, tend to have a harder time sleeping through the night. Parents whose infants sleep through the night generally rate their infant’s temperaments more favorably than parents whose infant continue to wake; however, it is hard to determine if a given temperament causes sleep problems or if sleep problems promote specific temperaments or behaviors.

Letting an Infant Cry
One popular notion is to let babies 'cry it out' when they are left alone. Letting babies "cry it out" is an idea that has been around since at least the 1880s when the field of medicine was in a hullabaloo about germs and transmitting infection and so took to the notion that babies should rarely be touched (see Blum, 2002).

In the 20th century, behaviorist John Watson (1928) applied the mechanistic paradigm of behaviorism to child rearing, warning about the dangers of too much mother love. The 20th century was the time when "men of science" were assumed to know better than mothers, grandmothers and families about how to raise a child.

A government pamphlet from the time recommended that "mothering meant holding the baby quietly, in tranquility-inducing positions" and that "the mother should stop immediately if her arms feel tired" because "the baby is never to inconvenience the adult." Babies older than six months "should be taught to sit silently in the crib; otherwise, he might need to be constantly watched and entertained by the mother, a serious waste of time." (See Blum, 2002.)

According to some behaviorists, children should be taught to be independent. However, some say that giving babies what they need now leads to greater independence later. In anthropological reports of small-band hunter-gatherers, parents took care of every need of babies and young children. Toddlers felt confident enough (and so did their parents) to walk into the bush on their own.

Some authors (e.g., Stein & Newcomb, 1994) say that caregivers who habitually respond to the needs of the baby before the baby gets distressed, preventing crying, are more likely to have children who are independent. Soothing care is best from the outset. Once patterns get established, it's much harder to change them.

Rats are often used to study how mammalian brains work and many effects are similar in human brains. In studies of rats with high or low nurturing mothers, there is a critical period for turning on genes that control anxiety for the rest of life. If in the first 10 days of life you have low nurturing rat mother (the equivalent of the first 6 months of life in a human), the gene never gets turned on and the rat is anxious towards new situations for the rest of its life, unless drugs are administered to alleviate the anxiety. These researchers say that there are hundreds of genes affected by nurturance. Similar mechanisms are found in human brains—caregiver behavior matters for turning genes on and off. (Work of Michael Meaney and colleagues; e. g., Meaney, 2001).

Some view the mother and child as a mutually responsive dyad; a symbiotic unit that make each other healthier and happier in mutual responsiveness. This expands to other caregivers too.

Babies' bodies become dysregulated when they are physically separated from caregivers.

Babies indicate a need through gesture and eventually, if necessary, through crying. Just as adults reach for liquid when thirsty, children search for what they need in the moment. Just as adults become calm once the need is met, so do babies.

There are many longterm effects of undercare or neglect in babies (e.g., Bremmer et al., 1998; Blunt Bugental et al., 2003; Dawson et al., 2000; Heim et al. 2003)

When the baby is greatly distressed, the hormone cortisol is released. In excess, it's a neuron killer (Panksepp, 1998). A full-term baby (40–42 weeks), with only 25% of its brain developed, is undergoing rapid brain growth. The brain grows on average three times as large by the end of the first year (and head size growth in the first year is a sign of intelligence, e.g., Gale et al., 2006). It is possible that neurons fail to become connected during times of extreme stress (need reference).

Disordered stress reactivity can be established as a pattern for life not only in the brain with the stress response system (Bremmer et al., 1998), but also in the body through the vagus nerve, a nerve that affects functioning in multiple systems (e.g., digestion). For example, prolonged distress in early life, resulting in a poorly functioning vagus nerve, is related disorders as irritable bowel syndrome (Stam et al., 1997).

Self-regulation is undermined. The baby is absolutely dependent on caregivers for learning how to self-regulate. Responsive care---meeting the baby's needs before he gets distressed---tunes the body and brain up for calmness. When a baby gets scared and a parent holds and comforts him, the baby builds expectations for soothing, which get integrated into the ability to self comfort. Babies don't self-comfort in isolation. If they are left to cry alone, they may shut down when faced with distress (Henry & Wang, 1998).

As Erik Erikson pointed out, the first year of life is a sensitive period for establishing a sense of trust in the world, the world of caregiver and the world of self. When a baby's needs are met without distress, the child learns that the world is a trustworthy place, that relationships are supportive, and that the self is a positive entity that can get its needs met. When a baby's needs are dismissed or ignored, the child develops a sense of mistrust of relationships and the world and self-confidence is undermined. The child may spend a lifetime trying to fill the inner emptiness.

Caregiver sensitivity may be harmed. A caregiver who learns to ignore baby crying, will likely learn to ignore the more subtle signaling of the child's needs. Second-guessing intuitions to stop child distress, the adult who ignores baby needs practices and increasingly learns to "harden the heart." The reciprocity between caregiver and baby is broken by the adult, but cannot be repaired by the young child. The baby is helpless.

Blum, D. (2002). Love at Goon Park: Harry Harlow and the Science of Affection. New York: Berkeley Publishing (Penguin).

Blunt Bugental, D. et al. (2003). The hormonal costs of subtle forms of infant maltreatment. Hormones and Behaviour, January, 237-244.

Bremmer, J.D. et al. (1998). The effects of stress on memory and the hippocampus throughout the life cycle: Implications for childhood development and aging. Developmental Psychology, 10, 871-885.

Dawson, G., et al. (2000). The role of early experience in shaping behavioral and brain development and its implications for social policy. Development and Psychopathology, 12(4), 695-712.

Catharine R. Gale, PhD, Finbar J. O'Callaghan, PhD, Maria Bredow, MBChB, Christopher N. Martyn, DPhil and the Avon Longitudinal Study of Parents and Children Study Team (October 4, 2006). "The Influence of Head Growth in Fetal Life, Infancy, and Childhood on Intelligence at the Ages of 4 and 8 Years". PEDIATRICS Vol. 118 No. 4 October 2006, pp. 1486–1492. http://pediatrics.aappublications.org/cgi/content/short/118/4/1486.

Heim, C. et al. (1997). Persistent changes in corticotrophin-releasing factor systems due to early life stress: Relationship to the pathophysiology of major depression ad post-traumatic stress disorder. Psychopharmacology Bulletin, 185-192.

Henry, J.P., & Wang, S. (1998). Effects of early stress on adult affiliative behavior, Psychoneuroendocrinology 23( 8), 863-875.