**6.2.2 Measures**

150 Epidemiology Insights

Verhulst and Koot (1995) hold the view that both approaches are needed, and that combining both by adding information from one approach that is not captured by the other

A classification scheme of externalizing behaviours developed by Frick and colleagues (1993) distinguishes four types of externalizing behaviour problems based on a metaanalysis of 60 studies involving more than 28,000 youth. The four behavioural clusters that emerged may be ordered along two independent dimensions (overt vs. covert; destructive vs. non-destructive) and were labelled opposition, aggression, property violations, and status violations. These behaviour clusters were also confirmed in independent studies of adolescents. Most mental health practitioners and researchers distinguish between two types of childhood conduct problems based on the age at which children show first symptoms and the persistence of the symptoms across development (Moffitt, 2003). The differentiation between childhood-onset and adolescent-onset conduct problems is based on results from the Dunedin Multidisciplinary Health and Development Study, a 30-year longitudinal study of 1,000 New Zealand youths (Moffitt et al., 2001). Moffitt et al. (2001) identified two developmental pathways for childhood conduct problems: the life-course persistent path and the adolescence-limited path. Children with life-course persistent conduct problems first show symptoms in preschool or early primary school. Partly consistent with this theory, four developmental trajectories were identified for boys' externalizing problems from ages 2 to 8 and 6 to 15 years in two samples (Nagin & Tremblay, 1999): a *persistent problem* trajectory, a *high-level desister* trajectory, a *moderate-level desister* trajectory, and a *persistent low* trajectory. In addition, Campbell et al. (2006) identified for physical aggression from 24 months to age 9 the following trajectories: very-low, lowstable, moderate-decreasing, moderate-stable, and high stable aggression. Schaeffer et al. (2003) identified four somewhat different pathways of antisocial behaviour from first to seventh grade within an epidemiological sample of boys: *chronic high, moderate* (and stable), and *increasing aggression* trajectories as well as a *nonaggressive* trajectory. Early, persistent externalizing problems (e.g. aggression), however, predicts a range of negative outcomes including poor emotion regulation and impulsive behaviour, school failure and dropout,

may increase our knowledge of children's psychopathology (Ferdinand et al., 2004).

peer problems, and adolescent delinquency (Patterson et al., 1989; Tremblay, 2000).

developmental course of externalizing behaviours.

**6.2 Methods** 

**6.2.1 Sample and design** 

Studies, in which researchers employed the empirical approach, have shown that between ages 2 and 9 children generally decline on externalizing behaviour measures (NICHD Early Child Care Research Network ECCRN; Shaw et al., 2003). Bongers et al. (2003) also found a decline in mother-reported externalizing behaviour problems for both boys and girls between ages 4 and 18 in a representative sample of over 2,000 Dutch children. The aims of the study were 1) to assess the prevalence and incidence of externalizing behavioural problems in children from kindergarten to primary school, and 2) to investigate the

In the present study, families with children aged 3 to 6 years were recruited in preschools in the city of Braunschweig (Germany), a moderately sized city with 250,000 inhabitants. Families were recruited for a universal prevention efficacy study of child behaviour problems. Study details for recruitment were described by Hahlweg et al. (2010). We first At pre-assessment, families provided information regarding their age, nationality, relationship to the child, education level, employment, receipt of social welfare assistance, and household income. They also provided data on the age and gender of the child of interest and any siblings.

Child mental health was measured during the preschool years by the German version of the Child Behavior Checklist (CBCL/1½-5; Achenbach & Rescorla, 2000; see 5.2.2). A recent study tested the generalizability of the seven-syndrome model in 23 societies (Ivanova et al., 2010). Findings from this study indicate that researchers (clinicians) can use the syndromes to assess preschool psychopathology. For the 2-year follow-up and after, the Child Behavior Checklist 4-18 (Arbeitsgruppe Deutsche Child Behavior Cheklist, 1998) was used. The scores from the parent-report were classified according to the manual into age- and sex-dependent categories which are based on the percentiles of the normative study.

The German ADHD Rating scale (FBB-HKS) is part of the comprehensive Diagnostic System for Mental Disorders in Childhood and Adolescence (DISYPS-KJ; Döpfner & Lehmkuhl, 1998) and can be rated by parents and teachers. This ADHD rating scale includes 20 items addressing symptom criteria of both ICD-10 and DSM-IV as well as additional criteria assessing symptom onset, symptom duration, pervasiveness and functional impairment. Internal consistencies were satisfactory to very good in the different representative samples (Döpfner et al., 2008). The DSM-IV recognizes three subtypes of the disorder - the predominantly inattentive type, the predominantly hyperactive-impulsive type and the combined type. Children were diagnosed with any ADHD if parents reported that six or more symptoms had persisted for at least 6 months.

The Epidemiology of Child Psychopathology: Basic Principles and Research Data 153

Fig. 1. Prevalence rates of externalizing problems and DSM-IV-disorders

Fig. 2. *Incidence rates of externalizing problems and DSM-IV-disorders*

least four of five assessments.

The developmental course of externalizing behaviour problems is presented in Table 2. Table 2 includes the developmental patterns of CBCL-Externalizing problems, DSM-IV ADHD- and DSM-IV ODD-disorders. Overall, we found three different patterns: the first group is *stable normal* – for each of the five assessments no borderline and clinical scores on the Child Behavior Checklist or no diagnoses of ADHD or no diagnoses of ODD were obtained. The second group of children is *temporary clinical* – for at least one assessment borderline and clinical scores on the Child Behavior Checklist or a diagnosis of ADHD or a diagnosis of ODD was seen. The third group (*stable clinical*) showed relevant externalizing symptoms on the Child Behavior Checklist or ADHD-diagnoses or ODD-diagnoses for at

On the CBCL Externalizing scale 61.0 % of the sample was stable normal; from preschool to primary school, mother's report resulted in T-scores < 60. In addition, 31.6 % of the children had deviant CBCL scores for at least one assessment point. The stable clinicalpattern (remaining deviant at least four times) occurred in 7.4 % of the sample. In

The German Conduct Disorder Rating scale (FBB-SSV) is also part of the comprehensive Diagnostic System for Mental Disorders in Childhood and Adolescence (DISYPS-KJ)*.* The rating scale includes 23 items using the symptom criteria of both the ICD-10 and DSM-IV, as well as additional criteria (e.g. symptom onset). Studies have supported the instrument's psychometric properties, showing good reliability and validity in both clinical and nonclinical populations (Döpfner et al., 2008). Children were diagnosed with oppositional defiant disorder (ODD) if parents reported that four or more symptoms had persisted for at least 6 months. All questionnaire assessments were conducted at five assessment points: pre-test, and 1, 2, 3 and 4 years after the first assessment (follow-up 1- 4).
