Letters to the Editor
Internalizing Antecedents of Conduct Disorder
Dear Editor:
This letter provides findings about the importance of early internalizing conditions for later externalizing disorders. Several lines of research suggest that behavioural abnormalities may often precede the onset of conduct disorder (CD). However, while there is evidence that attention-deficit hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD) precede CD (1), questions remain concerning the association with internalizing conditions. The nature of such a relation is still subject to alternative interpretations. The more consistent hypothesis is that internalizing problems are a reaction to CD, but other studies indicate that the internalizing symptoms predict externalizing problems that occur later.
To investigate present and lifetime behavioural patterns in a group of adolescents (n = 26, mean age 12.9 years, range 10 to 16 years) with CD we used Baum and Walker’s modifìed version of the Child Behaviour Checklist (CBCL), where parents are required to rate their children within 2 age periods: from birth to age 3 years (infancy) and from age 4 to age 10 years (childhood). The scores of the CD group were compared with those of a nonclinical group. From this study, CD seems to emerge during adolescence as a disturbance presenting a clear overlap between externalizing (score: 72) and internalizing (score: 68) dimensions. Such an overlap is still present during childhood when significant differences between childhood and adolescence do not emerge (internalizing score: 68 vs 68: P = 0.94; externalizing score: 72 vs 70: P = 0.32). From birth to age 3 years, the comparison between CD and the control group shows significantly higher mean scores for the CD group on both internalizing (63 vs 42: P < 0.001) and externalizing (57 vs 38: P < 0.001) scales, but with mean scores falling in the clinical range only for the internalizing dimension.
These data permit us to hypothesize that CD has both internalizing and externalizing antecedents during childhood, although families consult at adolescence only for externalizing symptoms. Our findings also support the hypothesis that CD has relevant symptoms in infancy, thus allowing us to underline the importance of early internalizing antecedents in CD. According to Aronen (2), the internalizing symptoms in our sample precede later externalizing problems. Luby also found an unexpectedly high level of internalizing psychopathology in a group of externalizing children under 5 years of age (3). This high level of internalizing psychopathology found in externalizing children might account for high rates of comorbidity and for difficulties in differential diagnosis with preschool children having bipolar disorders. The question of comorbidity with mood and anxiety disorders is very complex for CD, representing an area for further investigation that may have important clinical implications for treatment of young children with externalizing disorders. Moreover, depressive symptoms in childhood should be addressed to prevent later psychiatric problems, especially aggression, poor adaptive functioning, and low self-esteem (2).
Finally, a heterotypic developmental continuity can be hypothesized (4), where internalizing problems first occur in infancy and externalizing problems emerge later during childhood and mature during adolescence, giving rise to a clinical pattern of mixed internalizing and externalizing disorder. This perspective seems to disconfirm the alternative hypothesis that internalizing symptoms emerge as a consequence of externalizing problems.
References
1. Loeber R, Green SM, Keenan K, Lahey BB. Which boys will fare worse? Early predictors of the onset of conduct disorder in a six-year longitudinal study. J Am Acad Child Adolesc Psychiatry 1995;34:499-509.
2. Aronen ET, Soininen M. Childhood depressive symptoms predict psychiatric problems in young adults. Can J Psychiatry 2000;45:465–70.
3. Luby JL, Heffelfinger AK, Mrakotsky C, Hessler MJ, Brown KM, Hildebrand T. Preschool major depressive disorder: preliminary validation for developmentally modified DSM-IV criteria. J Am Acad Child Adolesc Psychiatry 2002;41:928–37.
4. Hofstra MB, Van der Ende J, Verhulst FC. Continuity and change of psychopathology from childhood into adulthood: a 14-year follow-up study. J Am Acad Child Adolesc Psychiatry 2000;39:850–8.
Filippo Muratori, MD
Francesco Salvadori, MD
Lara Picchi, PhD
Annarita Milone, MD
Pisa, Italy
|
