The Development of Circadian Rhythms in Human Infants

1 Introduction
Happiness is not a matter of intensity but of balance, order, rhythm and
harmony. Thomas Merton 1915 - 1968
1.1 Introduction
The first four postnatal months of life are one of the most critical periods in human
growth and development. During this time, complex developmental and
physiological changes are occurring at an incredible rate over a brief period of time;
one which accounts for a significant portion of the infant‟s total lifespan to date. The
consequences of a delay or malfunction during the assembly and stabilisation of the
physiological apparatus at this stage could be devastating; contributing and leading to
long term morbidity, increased vulnerability to disease and even mortality as
characterised by Sudden Infant Death Syndrome.
Neonatal physiology in the normally developing infant is an area that has not
traditionally been studied in great detail, when compared to other periods. In order to
understand malfunction; one must understand function and normality. This thesis will
seek to explore the complexities of the maturing physiological systems in newborn
infants, within the first four postnatal months; in the home environment within which
they are cared. To probe further into this critical and key stage of development, the
order, timing, interaction and relationships between the separate components of
physiology will be examined. Components parts of the physiological systems will be
considered in terms of 24 hour biological rhythms – as dictated by the body‟s preset
„master clock‟ - the suprachiasmic nucleus (SCN) and in terms of outputs of the clock
– genes, hormones and their influence on behaviour as manifest by infant sleep.
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