Health Psychology. Michael Murray
sceptical analysis to outlandish treatment claims. Carl Sagan and other wise people have suggested that ‘Extraordinary claims require extraordinary evidence’. There can be nothing more extraordinary or outlandish than the claims of homeopathic medicine. To turn our discussion full circle, there is not a single replicated piece of scientific evidence of a homeopathic remedy influencing the NS, ES or IS. The biological systems of the body carry the traces of every physical and mental stimulus we encounter. Homeopathic medicine leaves no trace. QED.
Future Research
1 Advanced imaging techniques such as ‘serial section electron microscopy’ could be applied to study the mechanisms of inflammation.
2 We need to know more about misalignments of the circadian clock, emotion, and susceptibility to inflammation and acute and chronic conditions.
3 PNI research is needed to investigate the relationships between individual differences in cognitive ability, such as IQ test scores and changes in the immune system.
4 We need more studies of the impact of psychological homeostasis on the development of physical illnesses.
Summary
1 Three important biological systems in health and illness are the nervous system (NS), the endocrine system (ES) and the immune system (IS). They activate and deactivate tissues, organs and muscles to control and regulate action, emotion and mental activity.
2 The NS uses neurotransmitters and the ES uses neuromodulators and hormones. The brain modulates the IS by hardwiring sympathetic and parasympathetic nerves to lymphoid organs. The IS modulates brain activity, including sleep and body temperature.
3 Two important classes of cell in the NS are neurones and microglial cells. Microglial cells are highly plastic and act as macrophage (‘big eater’) cells, the main form of active immune defence in the CNS.
4 Decisions made by the CNS are communicated via the peripheral NS to the effector division and inputs to the CNS are conducted by the afferent division. The autonomic nervous system deals with the non-conscious control of cardiac muscles, smooth muscles and glands, while the somatic nervous system deals with skeletal muscular responses in speech and behaviour.
5 The hypothalamo-pituitary-adrenal (HPA) axis produces corticotropin releasing hormone from the hypothalamus and conveys this to the anterior pituitary gland. The HPA axis has a primary role in emotion and stress. The amygdala triggers bodily responses to emotional events, including the release of adrenalin by the adrenal glands.
6 The endocrine system consists of the ductless glands and the hormones produced by those glands. Endocrine glands release their secretions directly into the intercellular fluid or into the bloodstream. Cellular metabolism, reproduction, sexual development, sugar and mineral homeostasis, heart rate and digestion are all regulated by hormones.
7 The ES regulates the circadian rhythm and sleep/waking cycle with a variety of hormone releases. Melatonin is produced in the pineal gland, under the control of the central circadian pacemaker in the suprachiasmatic nucleus (SCN) region of the hypothalamus.
8 The IS protects the body against disease or other potentially damaging foreign bodies. When functioning properly, the IS identifies and attacks a variety of threats, including viruses, bacteria and parasites, while distinguishing them from the body’s own healthy tissue.
9 Psychoneuroimmunology is the study of the interactions and relationships between psychological, neurological and immunological processes. Research over recent decades suggests that brain-to-immune interactions are highly modulated by psychological factors which influence immunity and IS-mediated disease.
10 The principle of physiological homeostasis is extended to psychological homeostasis. Identical mechanisms exist in both forms of homeostasis. In seeking to maximize physical and subjective well-being to a high set point, we approach new sources of potential reward and try to avoid aversive or confrontational situations.
3 Genetics, Epigenetics and Early Life Development
‘Health will be defined as a function of gene–environmental homeostasis.’
Dover (2009)
‘The brain is an extraordinary organ showing high levels of epigenetic features.’
Delgado-Morales and Esteller (2017)
‘While undernutrition kills in early life, it also leads to a high risk of disease and death later in life. This double burden of malnutrition has common causes, inadequate foetal and infant and young child nutrition followed by exposure (including through marketing practices) to unhealthy energy dense nutrient poor foods and lack of physical activity. The window of opportunity lies from pre-pregnancy to around 24 months of a child’s age.’
United Nations System Standing Committee on Nutrition (2006)
Outline
The passage from the gametes to a fully functioning adult human involves a matrix of intricate, interacting genetic and environmental processes. All living organisms store genetic information using DNA and RNA, with different genes having their expression switched on or off by DNA methylation. Genetic processes lay down scripts that are edited by epigenetic processes that produce lifelong alterations in individual development, health and disease. Early life development is a formative and critical stage that requires nurturing care for optimal outcomes and maximum protection from sources of adversity.
The 1971 novel The Dice Man by Luke Rhinehart tells of a psychiatrist who decides to make life decisions based on the rolling of dice. The Dice Man is based on a reckless and scary conceit which, due to its subversive content, with issues such as rape, murder and sexual experimentation, led to the banning of the novel in several countries, no doubt increasing sales. It is alleged that the author wrote the book based on his experiences of using dice to make decisions while studying psychology. The cover bore the confident sub-heading: ‘Few novels can change your life. This one will.’ However, another, more profound truth does not feature in The Dice Man story. That is the fact that the most crucial ‘dice of life’ are cast long before we can say ‘ABC’ – the dice of biological determination and early life development (Figure 3.1), the topics of this chapter.
Figure 3.1 The ‘dice of life’ – genetics, epigenetics, and early life development
Genetics and Heritability
The science of genetics began with Hippocrates. His theory of ‘pangenesis’ suggested that heredity material in the form of ‘pangenes’, collected from around the body, enters the sperm and ovaries. Information from specific parts of the parents’ bodies were communicated to the offspring to create the corresponding body part. For example, information from the parents’ hearts, lungs and limbs was believed to transmit directly from these body parts to create the offspring’s heart, lungs and limbs. The theory that inheritance was based on the ‘blending’ of parental traits was also popular and could not be dismissed until the research by Gregor Mendel (1822–1884), an Austrian monk. Mendel cultivated and tested the physical characteristics of 28,000 pea plants, which made excellent study items as they have easily recognizable and constant features, such as seed texture, colour and height. Mendel observed seven traits that existed in one out of two possible forms, for example the flower colour is white or purple, the seed shape is either round or wrinkled, and the seed colour and pod colour are both green or yellow. With only one of two possible results from cross-pollination, Mendel could determine which traits were passed down to the offspring with what frequency. The modern-day science of genetics was born.
A world-wide survey of human mitochondrial DNA (mtDNA)1 led to the claim that ‘all mitochondrial DNAs stem from one woman’ and that she probably lived around 200,000 years ago in Africa (Cairn et al., 1987). This prolific woman has