 6. Temperament  163
correlations between personality and dis -
orders on the two DSM axes of disorders, 
indicating that personality traits do not have 
a ‘privileged’ relation with Axis II personal -
ity disorders,” Clark (2005) concluded that 
it was “reasonable to pursue the possibility 
of a general model to explain personality– 
psychopathology relations rather than sepa -
rate models to explain relations between 
personality and each of the two axes” 
(pp. 510–511) and, accordingly, proposed an 
integrating hierarchical framework in which 
“adult personality traits emerge from three 
biobehavioral dimensions . . . and they share 
these genetic diatheses with later developing 
disorders” (p. 511), both clinical syndromes, 
such as major depression, anxiety disorder, 
and substance use disorders and personality 
pathology (PP).3
In this model, for example, the well- 
established associations between N/NE 
and a wide range of psychopathology (see 
Kotov, Gamez, Schmidt, & Watson’s, 2010, 
meta-  analysis) result from a shared underly -
ing temperament dimension of N/NE, cer -
tainly as a genetic diathesis, and perhaps 
also reflecting early environmental factors. 
Moreover, multiple types of evidence have 
established that N/NE is the primary com -
ponent of a broad dimension of “internal -
izing” pathology—  encompassing, for exam -
ple, mood, anxiety, eating, trauma-  related, 
and obsessive–  compulsive (OC) spectrum 
disorders—  that has emerged repeatedly in 
large-scale studies of comorbidity  (more 
precisely, co- occurrence,  but the former 
term is more typically used) among common 
mental disorders (see Kotov et al., 2017, for 
a comprehensive review and synthesis of 
this literature). Similarly, the temperament 
dimension E/PE underlies both the corre -
sponding personality trait and various types 
of psychopathology, particularly depressive 
spectrum disorders, many anxiety disorders, 
OCD, PTSD, anhedonia (e.g., in schizo -
phrenia/schizotypy), narcissism, and mania 
(Horan, Blanchard, Clark, & Green, 2008; 
Kotov et al., 2010; Watson et al., 2020; Wat -
son & Naragon-  Gainey, 2010).
In turn, the DvC personality factor has 
been linked with a second broad “exter -
nalizing” dimension of psychopathology, 
encompassing substance use disorders, anti -
social behavior, and various aspects of PP, that emerges in the aforementioned comor -
bidity studies (Kotov et al., 2017; Krueger 
& Markon, 2006; Krueger, Hicks, Patrick, 
Carlson, Iacono, & McGue, 2002). Evi -
dence also links this dimension (as well as 
N/NE) with attention-  deficit/hyperactivity 
disorder (ADHD) and so-  called “border -
line” PP (e.g., Nigg et al., 2002; Nigg, Silk, 
Stavro, & Miller, 2005). In Clark’s (2005) 
model, a DvC temperament dimension again 
underlies both the personality trait and re -
lated mental disorders. Moreover, tempera -
mental N/NE is posited to account for the 
moderate correlation between the internaliz -
ing and externalizing factors (e.g., Kendler, 
Prescott, Myers, & Neale, 2003). Finally, 
we (Watson, Clark, & Chmielewski, 2008) 
and others (Tackett, Silberschmidt, Krueger, 
& Sponheim, 2008) have proposed a sixth 
broad factor (i.e., beyond the FFM) of “odd -
ity” or “peculiarity” that integrates schizo -
typal PP and potentially other schizophrenia 
spectrum disorders into an encompassing 
hierarchical model of personality and psy -
chopathology. Indeed, “thought disorder” is 
a third higher-  order dimension of psychopa -
thology (along with internalizing and exter -
nalizing) that emerges in disorder comorbid -
ity analyses when sufficient exemplars are 
included (e.g., Caspi et al., 2014; Forbes et 
al., 2017; Kotov et al., 2010). Thus, accu -
mulating evidence increasingly appears to 
support the view that we proffered in the 
original edition of this chapter: It is more 
parsimonious to consider temperament di -
mensions as underlying both personality 
traits and various mental disorders than to 
view personality and psychopathology as 
separate domains that stand in some relation 
to each other.
Adopting this view of temperament in re -
lation to psychopathology has far-  ranging 
implications. First, it explains the exten -
sive comorbidity among psychological 
disorders—  which has been a major chal -
lenge to the current categorical system of 
diagnosis (e.g., Andrews, Slade, & Issakidis, 
2002; Bijl, Ravelli, & van Zessen, 1998; 
Clark, Watson, & Reynolds, 1995; Grant 
et al., 2004; Kessler, Chiu, Demler, Meri -
kangas, & Walters, 2005; Teesson, Slade, 
& Mills, 2009)—as being due in large part 
to shared underlying temperaments (Clark, 
2005, 2007); that is, persons with temper -