Page 120 - Read Online

De Francesco et al. J Transl Genet Genom 2024;8:102-18 https://dx.doi.org/10.20517/jtgg.2023.51 Page 106

Figure 1. Multivariate Cholesky model. Observed variables are depicted in squares and latent variables in circles. A: Additive genetic
factors; C: shared environmental factors; E: unique environmental factors.

posits that the correlations among the traits are influenced by both genetic and environmental factors [19,20] .
In the case of n variables, the Cholesky decomposition involves n separate genetic and environmental
factors: the first factor affects all traits, the second factor affects all traits except the first one, the third factor
affects all traits except the first two, and so forth . The Independent pathway model [Figure 2] suggests
[21]
that shared genetic and environmental latent factors have a direct impact on all the traits being studied.
These shared elements would influence the relationships among the traits, whereas a group of distinct
hidden variables would be accountable for the unique variability in each trait . Lastly, the Common
[22]
Pathway model [Figure 3] posits that genetic and environmental influences contribute to a single common
hidden variable ("Liability"), which in turn directly affects the observed traits. Furthermore, similarly to the
previous model, this one also includes latent factors specific to each trait, which represent the unique
components of variance that are not shared . During the statistical analyses, all models are compared to
[23]
each other through chi-square tests, and the selection of the best-fitting model is guided by the principle of
parsimony. According to this principle, models with fewer latent variables are preferred over the more
complete ones if they do not cause a significant worsening of fit to the data .
[23]
Internalizing and Externalizing Disorders
The terms Internalizing and Externalizing indicate two sets of behavioral, social, and emotional problems
typical of childhood and adolescence . These terms were first used by Thomas M. Achenbach with the
[24]
purpose to aggregate, using a factor analysis, psychopathologies diagnosed in a sample of 600 youths aged
between 4 and 15 years old. As a result, the authors were able to distinguish between disorders involving an
impairment that is less visible from the outside and more intrapersonal, called Internalizing disorders, and
disorders that significantly alter the interactions with peers and the surrounding environment, defined as
Externalizing .
[1,2]

[6]
This division has gradually been adopted by the American Psychiatric Association . The latest edition of
the DSM-5 labels as “Internalizing” those disorders primarily characterized by depressed mood,
physiological symptoms with their cognitive counterparts, and anxious symptoms . Whereas disorders
[6]
labeled as “Externalizing” are characterized by conduct disturbances, antisocial behaviors, impulse control
difficulties, and a tendency towards substance abuse behaviors . This distinction could promote the
[6]
development of diagnostic approaches different from the purely categorical ones that clinical psychology
has traditionally used, leaning towards an increasingly dimensional perspective . However, it should be
[6]
underlined that the existence and validation of these two broad categories do not aim at totally replacing the
more conventional and current categorical approaches: while acknowledging the distinction between INT-
EXT disorders, the DSM-5 continues to use labels to classify psychological distress into independent and
[25]
separate diagnostic classes with specific symptomatology, pervasiveness, and duration . However, the