Aodhán MoranWriting

Personality and Health Outcomes

A person and their health. A straight line from one to the other is begun and stops short; then a curved path of small steps is taken, each step darkening, and the person arrives at health the long way round

1. Introduction

Scholars and laypeople alike are fascinated by the question of why some people are healthier than others.

The relationship between personality and health has been studied for millennia, from the bodily humors of Hippocrates to the psychosomatic illnesses of Freud. However, many of these theories are now known to be riddled with conceptual confusion and misleading conclusions.

In contrast, the past century has seen substantial empirical research uncovering significant connections between personality traits and health outcomes. There is now a growing consensus in modern psychology that personality traits can influence health through a mix of behavioural, biological, and psychological factors.

In my discussion, I will delve into the historical context of personality and health, examining the relationships between health outcomes and 1) Type-A personality, 2) Type-D personality, and 3) the Five Factor Model (FFM). I will ultimately argue that while recent studies have revealed important associations between personality traits and health outcomes, the inherent complexities of both personality and health outcomes make it challenging to establish a direct causal link between them. ## 2. What is personality and how has it been defined? Personality is a complex phenomenon. The world presents us with a series of issues, and just as a carpenter shapes raw materials using their tools, personality may be broadly defined as a toolset for understanding and tackling life’s ceaseless problems.

Allport (1961) defined personality as the dynamic organisation within individuals of those psychophysical systems that determine characteristic behaviour and thought. Given that there is no one solution to all of life’s problems, each personality is suited to a particular type of environment that occurs often enough to keep it in the gene pool (Nettle, 2006).

Research has shown that personality traits are strong indicators of future health outcomes (Friedman & Kern, 2014). Theories of personality, by providing frameworks to categorize and predict behaviours, are instrumental in exploring the link between personality traits and health outcomes. ## 3. What are health outcomes and how have they been defined? Health outcomes (HO) are measured changes in the health status of an individual or group generally.

Three primary classifications of HO are identified by Strickhouser et al. (2017): 1) Mental health, which captures outcomes related to emotional, cognitive, and social health, like happiness or depression; 2) Health behaviours, focusing on activities that have an impact on health, for instance, exercising or engaging in risky sexual activities; and 3) Physical health, concerning the physical state of the body, which includes physical ailments like cancer, and ultimately, mortality.

Psychologists use HO measurements to explore the relationship between personality traits & specific HOs, such as quality of life, morbidity, or mortality. ## 4. Determining causality between personality and health outcomes Establishing a causal link between personality traits and health outcomes (HO) remains challenging. Research shows that while personality is connected to health over time, the nature of this relationship is complex, involving both causal and non-causal elements (Kern & Friedman, 2011).

Lee (2012) presents four potential reasons for correlations between variables: 1) Direct causation, where one variable (X) causes another (Y); 2) Common cause, where both variables (X and Y) are influenced by a third variable (Z); 3) Controlled collider, where controlling for a collider (Z) reveals a relationship between two variables (X and Y); 4) Emergent property, where both variables (X and Y) are indicators of a broader characteristic (Z).

To explain how personality impacts health, several models have been proposed, generally falling into three categories: 1) Behavioral mechanisms, where personality traits influence health-related behaviours; 2) Psychological mechanisms, encompassing coping styles; and 3) Physiological mechanisms, where personality traits affect physiological responses, which in turn impact health. However, a key challenge in the literature is distinguishing between the impact of personality traits on health outcomes and confounding factors that may predispose an individual to certain personality traits and health outcomes. ## 5. How has the relationship between personality and health been studied in the past? ### 1. Type A personality Empirical exploration of the relationship between personality and health can be traced back to the identification of Type-A personality (TAP). TAP is characterised by competitiveness, impatience, and hostility.

Decades of research pioneered by Friedman and Rosenman (1959) exploring the relationship between TAP and coronary heart disease (CHD) generally supported TAPs role as a risk factor in CHD incidence.

This is further supported by the Western Collaborative Group Study (WCGS), which found that TAP had twice as much CHD incidence at an 8.5-year follow-up compared to non-TAP participants. Critically, the association remained after controlling for a single predictive risk factor such as smoking, high blood pressure, or cholesterol or combinations of those risk factors (Rosenman et al., 1965), suggesting that TAP may be a causal factor in the incidence of CHD. ### 2. Type D personality Type-D personality (TDP), characterised by high negative affectivity and social inhibition, is another well-researched personality type. It is linked to the activation of the Hypothalamic-Pituitary-Adrenal (HPA) axis, a key part of the body’s response to stress. The HPA axis connects the nervous and endocrine systems and triggers cortisol release when stressed. Some authors suggest that TDP traits amplify the stress response via the HPA axis (Friedman, 2000).

Studies have shown a significant relationship between TDP and coronary heart disease (CHD), even after adjusting for other biomedical factors (Denollet, 1996). This was further supported by Williams et al. (2007), who found that men with TDP had higher cardiac output under stress than those without TDP, suggesting that TDP affects health by increasing cardiac output and stress perception.

Another study by Williams et al. (2008) in a healthy British and Irish population found that TDP prevalence was 38.5% higher, with fewer health-related behaviours and lower social support. This association persisted even when controlling for neuroticism, pointing towards a possible causal relationship between TDP and CHD incidence. However, many previous studies rely on data that are not nationally representative, which may limit the generalizability of their findings (Hampson et al., 2007). ## 6. What are the modern views on the relationship between personality and health? ### 1. Five-Factor Model Contemporary psychologists studying personality-health relations have largely embraced the Five-Factory Model (FFM) of personality. This is in part because the stability of these factors— openness to experience (O), conscientiousness (C), extraversion (E), agreeableness (A), and neuroticism (N)—have repeatedly replicated across samples and cultures (John, 2008).

Further, there is an enormous body of research exploring the personality–health connection using the FFM, with some estimating that over 850 studies investigated this relation (Strickhouser et al. 2017). Although it has its limitations, the FFM offers a general framework for causal explanations in personality psychology, which we can use as a basis to ground our explorations of the personality-health connection. ### Conscientiousness Research consistently shows that higher levels of C (characterized by orderliness, discipline, and perseverance) are linked to a lower risk of mortality. Conscientious individuals tend to engage in health-promoting behaviours such as safe driving, healthy eating, and low substance use (Bogg & Roberts. 2004).

Research has indicated that the impact of high C on positive health outcomes and longevity is stronger than many established psychosocial risk factors, such as socioeconomic status and intelligence (Roberts, 2007). ### Neuroticism Trait N has also been well-researched in its relation to health. N is characterised by emotional instability, volatility, pessimism, and a hostile interpersonal style. A long-term study showed that neuroticism is more predictive of subjective well-being than objective health measures (Friedman et al. 2010).

This suggests that while high neuroticism might not directly cause poor health, it significantly influences individuals’ perceptions and reports of their health. Moreover, it may indirectly affect health through behaviours and coping styles, such as dietary habits, exercise, or alcohol consumption.

People high in N might be more vigilant about their health, leading them to report more health issues even if they are objectively healthier and have longer lifespans (Friedman, 2010). ## Conclusion In summary, the relationship between personality and health is complex, involving a mix of causal and non-causal elements. The research reviewed indicated that certain personality configurations, TAP and TDP, are associated with increased negative health outcomes, such as CHD. On the other hand, personality traits identified in the Five-Factor Model (FFM) are seen more as emergent properties rather than direct causes of health outcomes. These traits, including C and N, while not direct causes themselves, are linked to health through their influence on various behaviours and attitudes. Consequently, it’s more likely that these traits indirectly impact health by shaping health-related behaviours.