774 vII. APPLICATIONS  AND  IMPLICATIONS
existing health trajectory and on situational 
exposures and responses.
A complete understanding of personal -
ity and health involves the complex mutual 
influences of personality change and health 
change. The associations between personal -
ity and health differ at different points in the 
lifespan (Shanahan, Hill, Roberts, Eccles, & 
Friedman, 2014), and the underlying mecha -
nisms to explain these associations are likely 
to involve complicated causal chains oper -
ating over time. Exciting progress is being 
made in the study of personality and health 
from a biopsychosocial, lifespan perspective.
The Outdated  Models
Although the idea of ties between personal -
ity and health dates back thousands of years 
to the bodily humors (blood, black bile, 
yellow bile, and phlegm) postulated in the 
writings of Hippocrates and Galen, it was 
not until the mid-20th century that scien -
tific study of personality and health began 
in earnest (Friedman, 2007). The work of 
the psychosomatic theorists and physicians 
on the ties between specific unconscious 
emotional conflicts and disease (e.g., Al -
exander, 1950) grew out of a neoanalytic 
framework and provided many observations 
and insights linking psyche and soma, but 
this approach was impossible to validate in 
a rigorous manner. For example, it could be 
documented that an emotionally conflicted 
and miserably unhappy woman would be ill 
more often (Dunbar, 1955), but neither the 
psychological predisposition nor the links 
to disease could be reliably assessed or ex -
plained.
In response to this turbidity of psychoso -
matic psychiatry, some researcher–  clinicians 
turned to a medically focused tack. The 
prime early example is the Type A behav -
ior pattern. Proposed by two cardiologists 
in the 1950s, the Type A pattern appeared 
predictive of coronary heart disease (Rosen -
man et al., 1964). The idea was to view Type 
A as a medical syndrome of coronary dis -
ease proneness and avoid ambiguous psy -
choanalytic concepts. Yet Type A people 
were defined as those hostile or aggressive 
individuals involved in a constant struggle 
to do more and more things in less and less time (“hurry sickness”), a personality-  like 
definition that invoked vague psychosocial 
concepts—  ambiguously proposed without 
a multitrait–  multimethod assessment of 
convergent and discriminant validity—  even 
as it sought to avoid them. The eventual 
(and ironic) result was thousands of stud -
ies with seemingly contradictory findings, 
as researchers began uncoordinated efforts 
to understand the measurement of Type A, 
the trait correlates of Type A, the subcom -
ponents of Type A, and the behavioral and 
developmental aspects of Type A (Houston 
& Snyder, 1988). Several decades of me -
andering research revealed the necessity of 
comprehensive models and rigorous assess -
ment if progress was ever going to be made 
regarding the relations of individual differ -
ences and health. The relevant processes un -
fold over time and necessitate a longitudinal 
approach (Friedman & Kern, 2014; Hamp -
son, 2012).
Simple Health–Behavior  Models
In health–  behavior models, personality traits 
influence the adoption or maintenance of 
health-  enhancing behaviors and the avoid -
ance of health-  damaging behaviors, which 
in turn affect health status and, ultimately, 
longevity. For example, a health–  behavior 
model may focus on the influence of person -
ality traits on smoking, drinking, diet, and 
physical activity (cf. Turiano, Chapman, 
Gruenewald, & Mroczek, 2015). A subclass 
of these models speaks of a so-  called “ad -
dictive personality,” prone to alcoholism, 
other drug abuse, uncontrolled overeating, 
or compulsive gambling. However, such ap -
proaches often do not address the earlier 
life influences, the moderators, the inter -
correlations, the interactions, the mediating 
psychophysiological consequences, and the 
ranges of health outcomes of these behav -
iors. Unhealthy behavior is not isomorphic 
with poor health, and there is substantial 
variation in what behavior patterns are help -
ful or harmful for different individuals at 
different times, and why.
Simple Stress‑to‑Disease  Models
Another basic approach to personality and 
health uses “stress” as the key explanatory 