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La Educación
Número: (134-135) I,II
Año: 2000

A Literature Review

At least six inter-related lines of research converge to support the existence of a synergetic relationship in which the psycho-social well-being of children affects their health and nutritional status as well as the reverse. Evidence will be presented below that is derived from research dealing with:

1. Stress. The effect of psychological stress on health;
2. Brain development. Animal research on brain development;
3. Touch. Effects of touch on low birthweight and premature babies;
4. Positive-deviance. Children who thrive in conditions that put them at risk;
5. Nutritional Recuperation. Effects of stimulation/affect on children in
nutritional recuperation centers; and
6. Planned interventions. Effects on children at risk or with moderate or mildly malnourished children.

1. Stress

People are exposed to stress when they are placed in situations requiring some sort of change or adaptation in response to novelty, uncertainty, or unpleasantness. These situations can be acute and short-lived or moderate and prolonged. Social and psychological sources of stress include such conditions as overcrowding, parental rejection, family discord, separation, violence, etc. Although stress is related to disease, stressful situations do not produce infection; rather, they create reactions that impair the ability of immune systems to function properly. If one is under stress and exposed to a disease, one is more likely to get sick.

Research examining psychosocial stress as it affects the functioning of immunological systems is providing evidence that, “... directs attention to interactions among social and psychological as well as biological factors in the etiology, course, and treatment of disease” (Jemmott and Locke 1984, p. 78). Summarizing, an extensive review of research, Jemmott and Locke contend that:

... the bulk of empirical evidence indicates that people who have been exposed to a high degree of recent life stress have greater degeneration of overall health, more disease of the upper respiratory tract, more allergies, a greater risk of hypertension, and greater risk of sudden cardiac death and coronary disease than do people who have been exposed to a low degree of life stress. Other research indicates that life-style factors and poor mental health, quite apart from life stress, are related to physical health status. (Ibid., p. 79)
The specific physiological mechanisms that underlie the relationship between stress and disease are being sorted out. Researchers are examining the effects of hormonal reactions to stress as they affect the immune system through such changes as the level of circulating antibodies, the ability of certain cells to destroy foreign organisms, and the ability of such cells to multiply. This continuing search takes as its starting point acceptance of the general relationship, now well-established, of the effects of stress on immune systems and, hence, on health status.

The degree to which stress influences disease varies from person to person. This variation is not only related to the timing, duration and proximity of the source of stress, but also to the adaptive capacity of each person. That adaptive capacity, or resilience, is affected in turn, by such personal characteristics as self-esteem, self-efficacy, and the sense of control over external events, as well as by the degree of social support available (Krantz and Glass 1984; Rutter 1985, Gentry and Kobasa 1984). These are psychological and social characteristics that can be fostered and that begin to appear in the very earliest months and years of a child’s development. They can be fostered by responding adequately to psychological and social needs, assuring children the experience of success and a sense of love and social support. Moreover, these responses require something more than attending to a child’s health and feeding a child.

Although most of the recent psycho-neuro-immunological research on the link between stress and disease has been done with adults (or with animals), there is little reason to believe that these same conclusions would not hold with young children (Garmezy and Rutter), and there is some reason to believe that they may be even stronger in children (Jemmott and Locke, p. 82).

Implications. The knowledge that healthy social and psychological experience helps an individual to cope with exposure to stress certainly provides a valid reason for attending to social and psychological development in the early years, when self-esteem (or a sense of failure) begins to form. However, there are also more immediate implications of social and psychological attention to (or neglect of) young children. The survival and health of children aged 0 to 6 living in stressful conditions can be affected dramatically. Failure to provide children with the psychosocial support needed for their development is a source of stress and at the same time deprives children of the chance to learn to cope with stress. Neglecting psychological and social development means that these children will be more susceptible to disease and to death than children whose needs are being met. Indeed, some of the earliest work on “separation” carried out by Bowlby demonstrates that, under particular conditions, separation of the child from a caregiver (usually the mother) to whom it had become “attached” could lead to death (Bowlby, 1969).

2. Brain development

A considerable body of research with animals suggests that early stimulation and an enriched environment can have beneficial effects on survival, maturation, growth, responsiveness to stress, and behavior (Newton and Levine 1988; Crnic 1983). In controlled experiments the environment of well-nourished and of previously undernourished rats was “enriched” by including in the environment playthings and other rats with which to interact. Comparisons were made with rats whose environment was not enriched. The results showed that an enriched environment can affect brain development and can partially compensate for effects of under-nutrition on development and behavior (Smart 1987). Specifically, when previously undernourished rats have been subsequently provided with adequate food and placed in different environments (enriched and impoverished), results show:
  • compensatory effects of enriched environments on brain weight, forebrain length and width, and on the depth, area synapses, synaptic disc diameter and dendritic branching with the occipital cortex.
  • that previous undernourishment did not impair the ability of the rats to respond to environmental enrichment.
  • that brain maturation of the environmentally enriched but previously undernourished rats always remained below that of the environmentally enriched but previously well-nourished rats.
Clearly, both nourishment and enrichment have effects on the growth and development of the brain. An enriched environment produced compensatory effects, and an undernourished state did not allow the experimental animals to live up to their potential.

Implications. Although the mechanisms producing these effects are still being discussed, it is clear that there is more to both achievement and growth promotion that increasing food intake, and a varied and enriched environment helps. Failure to provide young children with a stimulating and varied environment will negatively affect brain development.

3. Touch

One non-nutritional aspect of the social interaction between caretaker and infant that seems to have an effect on physical growth operates through the sense of touch. To a large extent, research examining the effect of touch on growth and behavior of infants stems from research with animals showing that handling, or touch, affects the level of growth hormone (Schanberg, Evoniuk, and Khun, 1984). It is hypothesized that the touch system is part of a primitive survival mechanism found in all mammals which depend on maternal care for survival in their earliest weeks or months. Absence seems to trigger slowing of metabolism (until the mother can return)- hence its need for nourishment is reduced. This is functional in the short run but leads to stunted growth if prolonged.

Turning this idea around, it is increasingly clear that touch seems to promote growth and brain maturation and has an effect on activity and behavior. In an intervention experiment, a group of premature babies in an United States hospital were lightly massaged and their limbs moved passively during three 15 minute periods per day for 10 days. As a result, the babies averaged a 47 per cent greater weight gain per day than other infants who were kept in incubators and were not massaged, even though the massaged infants did not eat more than the others. The massaged infants were also more active and alert during sleep/wake behavior sessions, and showed more mature signs on a variety of behavioral tests. Eight months later, they did better than the others on tests of mental and motor ability and continued their advantage in weight (Field, Bauer and Nystron 1986).

A study in south India (Landers 1989) showed that low birthweight babies who were massaged showed a remarkable catch-up in their weight and on a battery of developmental tests over a period of six months. This research showed a clear effect of mother-child interaction on both physical and developmental outcomes.

Massage is a common, but declining childcare practice found in many cultures throughout the world. Why the practice is so widespread is not known, but a reasonable guess is that it emerged from experience and became a socially institutionalized practice providing an effective and natural way to assist underweight babies to survive, grow, and develop in adverse conditions.

Implications. These research findings leave us with questions but, independent of the work on attachment (Harlow and Harlow 1966), give support to such common Third World practices as massaging, carrying babies on the back and sleeping with babies, all of which are ways of maintaining physical contact and communicating through touch. What comes through clearly is that caregiver-child interaction is very important for growth as well as mental development.

4. Positive deviance: children who thrive in “at risk” conditions

Most nutrition research has been directed towards discovering causes of malnutrition and identifying the effects of attention to malnourished children. More recently, another line has focused on children who grow up in conditions of poverty that often lead to undernourishment but who manage to be well-nourished. Why do some children thrive while others do not? What are the mechanisms of biological, social and behavioral adaptability that allow these “positive deviant” children to grow and develop well?

Zeitlin, Ghasserni and Mansour (1990) review 16 studies which compare children who thrive with those who do not. They also examine a large body of related research. The authors consider three kinds of correlates, noting the importance of 1) socio-demographic and 2) physiological correlates of malnutrition, and then focusing on another cluster of variables: 3) “the psychosocial and behavioral aspects of the mother-child interaction, their individual temperaments, and the social network supporting the dyad.” Their purpose was to learn from adaptive childcare and feeding behaviors and the social networks that support them.

The review examines energy metabolism, growth-related hormonal adjustments, immune responses of the body, and psychological stress as related to positive deviance. A link is made between psychosocial well-being, nutritional thriving, and a healthy condition. The importance of examining psychological as well as genetic or physiological factors is explained as follows:

The fact that some children are genetically more resistant than others adds to the unexplained variance in the results of psychological research, just as uncontrolled psychological factors add to the ‘noise’ in physiological findings. (Zeitlin, et.al., p. 33)

Zeitlin, et al., go on to say:

Stressful caretaker-child interaction can be expected to increase protein requirements while tending to decrease the amount of food that the child consumes. Pleasantly stimulating interactions, on the other hand, enhance the child’s tendency to exercise its developing organ systems and hence to utilize nutrients for growth and development. (p. 33)

In short, psychological stress has a negative effect on the use of nutrients whereas psychological well-being stimulates the secretion of growth-producing hormones. “These mechanisms help to explain how psychosocial factors, such as the affect between mother and child, are associated with adequate growth and development” (Zeitlin et al., p. 34)

Implications. There are positive caregiver-child interactions and conditions of social support that are specifically adaptive in protecting the nutritional status and health of infants and young children. (p. 36)
  • Positive caregiver-child interactions
From their review, Zeitlin, et al. identified characteristics of caregiver-child interactions associated with adequate growth and development:
  • Frequent interaction (holding, hugging);
  • Rapid, consistent, and appropriate response to perception of a child’s needs;
  • Speaking and responding to a child’s vocalizations, both when holding the child and when the child is at a distance;
  • Looking directly into the child’s eyes;
  • Showing affection by smiling and friendly behavior rather than inflicting hostile or dominant behavior;
  • Permitting the child to imitate and guide interaction;
  • Avoiding interaction that is too slow or too rapid and overstimulating;
  • Giving clear instructions;
  • Rewarding achievements;
  • Reprimanding without being brusque, harsh, or severe;
  • Avoiding forms of control in which the only objective is to demonstrate authority over the child;
  • Creating a stimulating physical environment for the child.
 A nutrition-related intervention related to positive deviance was found to be actively feeding toddlers instead of expecting them to feed themselves.

Although these observations need to be associated with age and elaborated to give a more specific idea of how and what to do, that is not our purpose here; rather, we are concerned with establishing the general principle that actions to improve psychosocial well-being will affect growth.
  • Social support
The efficiency and quality of the network of social support available to caregivers figures prominently in the identification of children that thrive in conditions of risk. A supportive system (or family or community) helped to moderate effects of overwork as well as of stress and depression. The importance of social support noted in the Zeitlin review is also a central finding in one of the most detailed positive deviance studies that has been carried out, following a group of multiracial children from different social backgrounds in the same Hawaiian community from the prenatal period to the threshold of adulthood. In their book, Vulnerable but Invincible, Werner and Smith (1982) identify protective factors within the child and the caregiving environment that differentiate high-risk children who are resilient from those who develop serious learning and behavior problems. The major sources of support within the caregiving environment were (p. 134):
  • Four or fewer children spaced more than two years apart;
  • Much attention to the infant during the first year;
  • Positive parent-child relationship in early childhood;
  • Additional caretakers besides the mother and care by siblings and grandparents;
  • Steady employment for mother outside the household;
  • Availability of kin/neighbors for emotional support;
  • Structure and rules in the household and shared values — a sense of coherence;
  • Close peer friends and availability of counsel;
  • Access to special services.
In summary, these studies of “positive deviant” and “resilient” children help to identify conditions and behaviors that permit some families to bring up well-nourished children in spite of the conditions of poverty in which they live. They draw upon and reinforce other lines of research demonstrating the interaction between nutritional and non-nutritional behaviors and between a child’s characteristics and the environment in which the child grows and develops. Crucial features of that environment are the relationship of the child with its caregiver and the psychological and social support available to the caregiver.

5. Nutritional recuperation

Whereas the studies of positive deviance compare children of different nutritional levels experiencing different environmental conditions, studies of children in recuperation centers examine what happens to children who are all seriously undernourished when they are exposed to a different type of environment. Two telling examples come from Chile and Jamaica where experimental studies were set up in nutritional recuperation centers. The studies compared a) the progress of children who received a treatment of stimulation and play as well as food with b) the progress of those who received only food (Chile) or those who were well-nourished (Jamaica).
  • Chile
In the Chilean experiment (Monckeberg 1986), infants were fed, provided with psycho-sensory stimulation (for about 30 minutes twice a day), with physical exercise (also about 30 minutes twice a day), and with opportunities to play with children with similar characteristics who received the same diet but no psychomotor or affective stimulation.

For the stimulated children:

Not only was the weight gain different, but the physical growth was better and there was a significant difference after 50 days of treatment. The psychomotor quotient also exhibited the same pattern. While for the control group the average quotient was 65 (plus or minus 12) at the 150th day of treatment, for the experimental group it was 85 (plus or minus 7). Monckeberg, p. 28

These differences, for weight, psychomotor and mental development were more pronounced for children who were less than 6 months of age at admission to the recuperation center than for those between 6 and 12 months of age.

To explain the differences in recovery, Monckeberg hypothesizes that stimulation and affect trigger and help reinitiation of growth. He then makes reference to the links mentioned above relating resumed growth to biochemical processes and to the functioning of growth-producing hormones.
  • Jamaica
The Jamaican study (Grantham-McGregor 1984) compared three groups of children. Two of the groups had been admitted to the hospital for nutrition recuperation and one group was well-nourished but admitted for other reasons. In the recuperation program, one group of malnourished children was also provided with psychosocial stimulation, the other was not. The stimulation consisted of instructing attending nurses to play with the children for one hour each day.

When children entered the hospital, both malnourished groups had similar developmental quotients and were significantly behind the control group. By the time they left, all three groups had improved, but the intervened group had improved the most and was no longer significantly behind the control group.

One of the more interesting features of these two studies is that they both followed up the children after leaving the recuperation center. In the Jamaican case, that follow-up included an active program of home visiting using community health workers (CHW). The CHWs visited homes once per week over 24 months. Visits included reinforcement of the need for psychosocial interaction as well as monitoring of the physical status of the children. During this time the weight recuperation was maintained. The gains registered in psychosocial development were maintained as well, so that the children who had been played with in the hospital continued on a par with the comparison group of well-nourished children when followed over a period of 36 months. In the Chilean case, no additional action was taken following departure from the recuperation center. As contrasted with the Jamaican study, the Chilean follow-up led to the conclusion that the program of stimulation succeeded in raising mental performance only for the period of the program. A decline was observed when the children went back to their former environments. By way of comparison, in a small group of 35 recuperated children, who had been adopted after discharge by families of higher socioeconomic status, mental ability scores were normal, well above the scores quoted above.

Implications. Psycho-social stimulation as well as feeding is important in helping malnourished children recover their rate of growth. We see an effect of stimulation on nutrition.

6. Planned interventions

Yet another form of evidence supporting the importance of attending to both nutritional and non-nutritional conditions affecting growth and development comes from studies of intervention programs carried out in conditions of everyday life where many children suffered from mild to moderate malnutrition. In several instances, interventions have been designed to try to sort out effects from nutritional supplementation and effects from non-nutritional interventions intended to improve psycho-social development.

In an extraordinary study carried out with families in poor neighborhoods of Bogota, Colombia, 280 Colombian infants at risk of malnutrition were randomly assigned to one of four experimental groups formed by the presence or absence of one, or both, of two interventions: 1) nutritional supplementation for all members of the family, from the last trimester of pregnancy until the target child was three years old; and 2) a twice-weekly home-visiting program designed to promote early cognitive development, from birth of the target child until age three (Super et al., 1987). All families received free medical care and were studied prospectively.

The following extract summarizes some results: At three years of age, children who had received nutritional supplementation averaged 3 centimeters and 800 grams more than controls: the incidence of children with severe growth retardation was reduced by half. Home visiting had no overall effect on size but did reduce the number of severely underweight children. At age six (three years after intervention) the Supplementation effects remained at about the same magnitude. Children in the Home Visit condition had become larger than controls, by 1.4 centimeters and 483 grams. Both interventions reduced the incidence of stunting and wasting. Dietary recall data suggest that changes in family functioning as well as biological mechanisms account for the observed pattern of results. The effects noted for the Bogota experiment were greater for lower levels of father’s education.

A host of other studies could be cited (see review by Pollitt 1987) to support the contention that nutrition interventions can have short- and long-term effects on some aspect of behavior such as improved attention, heightened social responsiveness, reduced irritability and inability to tolerate frustrations, higher activity levels, and increased independence. These behaviors are related to both cognitive and social behavior in the long run.

What causes these effects? How should these findings be interpreted? Pollitt (1987) suggests that, in much of the literature, interpretation has been built around a model based on the biomedical tradition of disease causation that did not take into account the social context in which development occurred or the previous and subsequent history of an individual. This static, linear model and interpretation contrasts with another model beginning with the premise that “through its interactions with illness and adverse family and socio-economic conditions, under-nutrition increases the probability of diverting the trajectory of mental development...” (Pollitt 1987, p. 19). It also differs from a view that “effects may occur within a synergistic system where the malnourished infant is less successful at engaging caretakers in interaction and, in turn, is responded to less often and with less sensitivity, resulting in a failure to develop normal patterns of social interaction” (Lester 1979, as quoted in Barrett et al., p. 542).

Slowly, an interactive view is being recognized and used as a basis for designing as well as reinterpreting research results. For instance, in a study of food intake and human function carried out in Mexico (as part of a three-country study including Egypt and Kenya), the interactive model serving as the basis for analysis of cognitive performance and social conditions was as follows:

... one pathway by which low intake may affect development is through subtle effects on the young child’s manner of interacting with his or her environment, including reduced activity, attentiveness and social responsiveness. These behaviors, which lead to reduced stimulation and hence reduced opportunity for more complex responses, may also affect the child’s intake, perpetuating continued low intake because he or she does not ‘demand’ food. Similarly, development may be compromised by an interaction between child passivity and maternal time allocation in households where child care time is limited because the caretakers are pushed by economic necessity to long hours of work. In such a situation, low intake in the child interacts with the behavioral consequences of poor economic resources, with each component contributing to and reinforcing less than optimal outcomes. (Chavez et al., 1987, p. 298)

Following this model, a measure of cognitive development for children at 30 months was related to measures of 1) growth (length), 2) caretaking (using the observed appearance of the child as a proxy for maternal caretaking), 3) current diet, and 4) socioeconomic status. In a series of regression analyses allowing a look at different combinations of the variables, cumulative growth was the dominant significant variable, but caretaking and SES, were also significant. When all four variables were entered, length and child care continued to be significant.

The analysis lends support to an interpretation of development that looks at the interaction between the characteristics of the child and its environment, including interaction with the caregiver and with the conditions surrounding both the caregiver and the child. The researchers concluded that:

Social-environmental conditions of the household (as measured by socioeconomic status indicators and maternal caretaking) clearly affect development. The biological and behavioral experiences of the child, as reflected in growth, also affect development. The mechanism of these effects is probably synergistic. That is, child nutrition, health and activity ... have a synergistic relationship with respect to social and social-relational conditions, with respect to risk of poor or delayed cognitive development. The model is analogous to the dynamic interaction of infection and malnutrition, which have a synergistic relationship with respect to mortality. (Chavez, et al., 1987, p. 303)
Focusing on weight instead of cognitive development, and on infants, aged 0 to 6 months, a similar kind of interaction seems to be present. Infants increased faster in weight from birth onwards if the exterior and interior sanitary conditions of their homes were better, and if the preschoolers and mothers of the household appeared cleaner ... (p. 327). The implication is that nutrition interacted with an environmental condition related to better health and to better maternal care, as represented in the attention given to cleanliness of the house.

These six lines of research go a long way toward establishing the synergistic nature of the relationship between psychosocial status and health and nutritional status. An even more complete review would also draw on other strains of research including: 1) anthropological research which examines the wisdom embodied in so-called “traditional” medicine (see, for example, Neguissie 1988; Choppo 1988), 2) research dealing with practices and traditions of various currents of non-Westem medicine (e.g., Wu 1982) or 3) research on “psychosomatic” illness. Indeed, medical anthropology, behavioral medicine, and psychiatry all suggest a close connection among social, mental and physical well-being.