Abstract :
This special section exemplifies and offers a number of important methodologic and conceptual
advances that should provide investigators new tools for understanding comorbidity of child and adolescent
psychopathology, including (a) the importance of making careful methodologic distinctions in
how comorbidity is defined and operationalized, (b) specifying and justifying how data from different
sources are combined, (c) teasing out the impact of potentially confounding risk factors that lead to
symptom and syndrome overlaps, and (d) exploring the effects of time, timing, and order of disorder
emergence on variable manifestations of comorbidity. These advances are much needed, but may still
prove insufficient, given the daunting challenges in fully understanding comorbidity. Thus, future studies
should be characterized by (a) more focused search for subgrouping factors and interactions related
to the emergence of comorbidity, (b) careful exploration of setting- and/or informant-specific types
of psychopathology, (c) development of studies that explore not just phenotypes and genotypes, but
also environtypes and trajectory-types, (d) more discriminative use of information sources, including
explicit efforts to reconcile (rather than combine) discrepant information, (e) clear descriptions and
logical justification of when conjunctive, disjunctive, additive, and discriminative combinatorial approaches
are used, (f ) increased use of multidisciplinary research methods and teams, (g) increased
application of multiple lines of evidence in comorbidity studies, (h) increased focus on understanding
illness processes rather than just psychopathologic states, (i) development of creative new research
designs, and (j) redrawing disorder boundaries when warranted.
