Personality and Disease

Scientific Proof vs. Wishful Thinking

Christoffer Johansen

• Publisher: Academic Press
• Year: 2018
• ISBN:
  9780128054451
• Topic: Psychology
• Subtopic: Physiological Psychology
• Index: Psychology

A tremendous amount of research has been performed looking at the relationship between personality and disease. Research on this topic has been spread throughout scientific journals on psychology, behavioral health, psychoneuroimmunology, oncology, and epidemiology. Personality and Disease brings this research together in one place for the first time.

With contributions from world experts, the book summarizes research findings on personality as it relates to cancer, heart disease, diabetes, asthma and allergies, dementia, and more. Is there such a thing as a cancer- prone personality? Do sadness, anger, stress, or shyness affect the likelihood that we will fall ill to specific diseases? Can we protect ourselves from disease through a positive outlook?

This book will address both what we know, and what we persist in believing despite evidence to the contrary, and why such beliefs persist in the face of evidence.

• Investigates whether and how personality affects disease generally
• Includes cancer, heart disease, diabetes, asthma, allergies, and dementia
• Separates fact from fiction, evidence from beliefs
• Collates research from a wide variety of scientific domains
• Contains international perspectives from top scholars

Chapter 1

A Brief Historical Overview on Links Between Personality and Health

Jesper Dammeyer, and Ingo Zettler Department of Psychology, University of Copenhagen, Copenhagen, Denmark

Abstract

Throughout the history of (Western) medical science and philosophy, a connection between an individual's health and personality has been suggested. Indeed, many theories or models directly linking personality factors to one's health have been introduced, and many personality characteristics have been considered with regard to their importance for health. However, not all theories and models that link personality to health have been supported empirically. Herein, historical theories and models are described briefly, e.g., Hippocrates' ancient model of four human temperaments and Type A and Type B personalities. Furthermore, a broad overview of current and scientifically investigated personality constructs and their associations to health is provided, spanning across the so-called “Big Five,” together with gender, intelligence, emotional intelligence, and motivational factors. Finally, methodological challenges and future directions in research on health and personality are discussed.

Keywords

Disease; Gender; Health; Individual differences; Intelligence; Motivation; Personality models; Personality traits

A Brief Historical Overview on (Assumed) Links Between Personality and Health

For centuries, people have been interested in, and believed in, links between personality and health. However, not until recently such links have been investigated via thorough empirical studies. Personality is often understood as a set of (relatively) stable individual differences, encompassing factors such as gender, mental abilities, or traits. Personality factors have been found to be associated with the way people think, feel, or act with regard to virtually all areas of humans’ lives, including health. In this chapter, we provide a brief historical overview on theories, models, and empirical findings that have linked personality to health.

The Neolithic Age, Ancient Greece, and the Middle Ages

Ancient excavations from prehistoric Neolithic times have found human skulls with small drilled or scraped holes, caused by a surgical intervention called “trepanation” (Prioreschi, 1991). A dominating theory is that these holes were made in order for evil spirits causing mental disorders to leave the ailing body. Thus, very early in the history of civilization human believed in close links between the mind and the body.

In ancient Greece, Hippocrates (c.460–370 BC) introduced a theory of four temperaments, which is the first written theory on links between personality and health known today, although his temperament theory took its origin in the even older Egyptian and Mesopotamian philosophy of “humorism” (Sudhoff, 1926). Hippocrates’ temperament theory suggests that four bodily fluids (called humors)—namely, black bile, yellow bile, phlegm, and blood—directly affect an individual’s personality, behavior, and health (Johansson & Lynøe, 2008). Thus, in contrast to theorizing around trepanation, Hippocrates did not attribute mental illness (or other diseases) to evil spirits but to physiological reasons, in terms of imbalances of circulating body fluids that also affected one’s personality.

Based on Hippocrates’ theory, another ancient Greek physician, surgeon, and philosopher, Galen (c. AD 129–200), described in his dissertation De temperamentis—the first typology of temperaments. This typology was based on the four humors and considered the balance and imbalance of temperament pairs. According to Galen, the imbalance of pairs resulted in one of the four temperament categories (or personality types): sanguine (being optimistic and social), choleric (being short-tempered and irritable), melancholic (being analytical and quiet), and phlegmatic (being relaxed and peaceful).

Hippocrates’ and Galen’s humoral theory was dominant in Greek, Roman, as well as Islamic philosophy and medicine for many centuries. Not until the 19th century with the advent of modern medicine was Hippocrates’ and Galen’s theory substantially challenged, although it continued to be used by some researchers and practitioners in the 20th century (Marks, Murray, Evan, & Willig, 2000).

However, the Middles Ages should briefly be mentioned here, in which the religious belief that diseases reflect punishment by the Christian God dominated. Nonetheless, even in the Middle Ages, the (less religious) belief in a connection between physical illnesses and underlying personality (as introduced by Hippocrates and Galen) managed to coexist with established Christianity (Morrison & Bennett, 2006).

The Renaissance and the Age of Enlightenment

Even in light of the scientific revolution commencing in the 1600s following the Renaissance and onwards, increased knowledge about physiology and medicine, i.e., more solid empirically based models linking personality and health, was not developed before the 20th century. One explanation for such a late introduction and interest in the empirical study of links between personality and health might be the dominance of dualism in medicine. More precisely, the highly influential philosopher René Descartes (1596–1650), like the ancient Greeks, believed that the body and mind were separate entities, though interactions might be possible. The mind (including personality) was immaterial and distinct from the body, and, thus, the body was the object for scientific investigation and the mind was left for theologians and religion (Descartes, 1641, pp. 1–62). Descartes’ (and others’) dualistic view probably fed a mechanical and biomedical model of health—leaving little or no space for scientific investigations of how personality, cognition, or social and cultural factors affect health.

Personality and Health in the 20th Century

In the last century, more and more theories or models about human personality have been introduced. Besides psychoanalytic and psychodynamic approaches (for an overview, see Mitchell & Black, 1996), which will not be described herein, the most influential theories and models subsume similar personality characteristics to a broader trait. An important difference between such models and earlier ones was that the new models were, at least to some degree, based on empirical studies. Gordon Allport (1897–1967) is considered to be the founder of this empirical approach to personality psychology and the forerunner of modern personality trait models (see below). He is known for using what was later called, the “lexical hypothesis,” stating that individual differences are reflected in language terms. Allport et al., as well as researchers following this idea, read through dictionaries, searching for personality-descriptive words. These words were then further categorized (e.g., to delete exact synonyms), and a smaller subset of them was finally presented to people who should rate themselves or others based on these words (Allport, 1961).

In line with Allport’s work, Hans Eysenck (1916–97) made significant contributions to modern personality psychology and was one of the first to analyze personality differences using psychometric methods. Eysenck’s personality model first consisted of two factors, Extraversion (E, the tendency to enjoy social events and interaction) and Neuroticism (N, the tendency to experience negative emotions), which he argued were biologically/genetically based and reflected Hippocrates’ four temperaments: high N and high E = choleric type, high N and low E = melancholic type, low N and high E = sanguine type, and low N and low E = phlegmatic type (Eysenck & Himmelweit, 1947). A third dimension, psychoticism, was later added by Eysenck to the model, but it received little empirical support and will not be discussed further herein.

Another early attempt following an empirical approach is the Type A and Type B personality theory (Friedman & Rosenman, 1959). Being cardiologists, Friedman and Rosenman suggested that Type A personalities had a greater risk of developing coronary heart disease. Individuals with a Type A personality were described as being more ambitious, aggressive, competitive, impatient, and outgoing, and, in turn, as high-achieving “workaholics” who were more likely to push themselves with deadlines. Individuals with a Type B personality, by contrast, were described as more reflective, relaxed, and, in turn, as people focusing less on winning or losing when facing competition. Even though the Type A and Type B theory was empirically supported in some early studies, later empirical studies have not been able to replicate the empirical evidence (Šmigelskas, Žemaitienė, Julkunen, & Kauhanen, 2015). Consequently, the theory is only rarely used in research nowadays.

Current Models of Links Between Personality and Health: (Basic) Personality Traits

In recent decades, the most influential personality models—and also in general those most strongly supported empirically—have been models proposing basic personality traits. As described above, such models of basic personality structure have typically emerged from lexical studies in which people are asked to describe themselves or others via personality-descriptive adjectives (typically put in different contexts) initially found in dictionaries. These self- and/or other ratings are then grouped in a way (typically, using factor analytic techniques) such that similar adjectives (characteristics) form a trait, while the so-formed traits should be unrelated to each other.

Over the last decades, and due to better empirical studies, a personality model consisting of five traits has become an even more influential model than Eysenck’s “Big Three” (John, Naumann, & Soto, 2008). The five-factor model comprises the five basic traits of Openness to Experience (sometimes called...