**5.1 Background**

144 Epidemiology Insights

DSM diagnostic criteria with impairment measure, for example the Children's Global Assessment Scale (CGAS; Shaffer et al., 1999). The newest versions of some psychiatric interviews such as the Diagnostic Interview Schedule for Children (DISC; Shaffer et al., 2000) and the Child and Adolescent Psychiatric Assessment (CAPA; Angold & Costello, 2000) have included impairment criteria. Because many children who meet criteria for DSM disorders are not greatly impaired in their everyday functioning, the addition of impairment measures results in a decrease of prevalence rates. In a Dutch prevalence study, for example, the prevalence of 21.8 % of children who met criteria for any DSM-III-R disorder based on parent interview information dropped to 5.9 % when combined with a CGAS score indicating definite impairment (Verhulst et al., 1997). Conversely there are also many children who can be regarded functionally impaired but do not meet criteria for DSM diagnoses. Some 50% of children attending clinics in the Great Smoky Mountains Study do not reach DSM or ICD criteria for a diagnosis and yet half of these are significantly impaired

Of many factors that have been tested for association with prevalence in general population studies, findings for gender, age, SES, and degree of urbanization will be discussed here, because those are factors with findings that have been replicated across studies (Achenbach

*Gender:* Gender differences in prevalence are very robust across cultures, informants and across types of studies, in particular those that used rating scales and those that used DSM diagnostic criteria. Girls score higher than boys on internalizing psychopathology such as anxiety, depression and somatic complaints, and boys score higher than girls on externalizing behaviours such as attention and hyperactivity problems and aggressive and delinquent behaviours. These gender differences are found for both parent- and selfreported problems. Despite the range in cultural, economic, political and genetic differences, there is consistency in population-based findings that boys have more externalizing and

*Age of children and adolescents*: From a developmental perspective, the effects of age on levels of psychopathology in individuals can best be studied through longitudinal studies. For public policy purposes, cross-sectional data on prevalence with age can be important for service planning. Age interacts with gender as a factor associated with prevalence. Boys show more problems than girls when they are younger, whereas girls show more problems than boys in adolescence (Achenbach & Rescorla, 2007). In a multicultural study of selfreported problems across 7 countries, both internalizing and externalizing behaviours increased with ages 11 to 18 years. In another multicultural study of parent-reported problems of children aged 6 through 11 years across 12 countries, and aged 6 through 17 years in 9 countries, externalizing problems decreased and internalizing problems increased with age (Achenbach & Rescorla, 2007). Although parents and adolescents agreed in reporting increases with age of internalizing problems, they disagreed about externalizing problems. Apparently parents are increasingly unaware of their child's externalizing behaviours with increasing age. This is probably caused by a developmental shift in type of externalizing problems, with overt physically aggressive and oppositional behaviours decreasing with age and status violations such as truancy, running away from home, and

in their social functioning (Angold et al., 1999).

**4.3 Factors associated with prevalence** 

girls have more internalizing problems.

substance abuse increasing with age (Bongers et al., 2003).

& Rescorla, 2007).

Behavioural and emotional disturbance are very common among children and adolescents. Approximately 20 % of children in Western, industrialized countries experience the signs and symptoms that constitute internalizing (e.g. anxiety/depression, withdrawal) or externalizing (e.g. oppositional defiance, aggression) DSM-IV disorders (Tolan & Dodge, 2005). Recently, epidemiological research has begun to focus on children younger than six and to consider the clinical significance of behavioural and emotional problems of this period of the life span (Angold & Egger, 2007). A review on the epidemiology of emotional and behavioural disorders in preschool children estimated the overall prevalence of 'problematic' behaviour as lying at somewhere between 7 % and 25 % (Egger & Angold, 2006). Empirical findings illustrate a first peak in multi modal distribution of mental health service utilization in childhood in 6-9-year-old children (e.g. Campbell, 2006). This raises the question of whether child psychiatric disturbance pre-exists school attendance, but remains undetected.

In a study in the US, Wadsworth and Achenbach (2005) reported differential incidence by SES for elevated scores on internalizing and externalizing disorders. It is not yet clear whether these findings can be generalized outside of the US, and to preschool age and other informants. From a multicultural perspective, Achenbach and Rescorla (2007) specified in their comprehensive review the need for comparable data on preschool-aged instruments. The aims

The Epidemiology of Child Psychopathology: Basic Principles and Research Data 147

(T = 60 - 63 for problem scales, T = 65 - 69 for syndrome subscales) and *clinically relevant* behaviour (T ≥ 64 for problem scales, T ≥ 70 for syndrome subscales). Associations between problem scale prevalence and demographic and socio-economic factors (e.g. child´s age and gender, single parenthood, parents' education, family income, migration status) were carried out with Chi square statistics, and the significance level was set at *p* < .01. To determine whether children who had deviant problem scores (T ≥ 60) were at higher risk of having a demographic (economic) factor, odds ratios (OR) and 95 % confidence intervals

Table 1 reports the prevalence rates of problem scales and syndrome subscales for different informants. In this sample, the prevalence rate of *Internalizing* problems varied from 7.3 % (fathers) to 12.0 % (mothers) in the borderline range. Across informants, about 12 - 13% of the children met the criterion of the clinical range. For internalizing syndrome scales, 5 - 6 % prevalence rates were obtained for predominantly clinically relevant somatic complaints, anxious depressive behaviour, and withdrawn behaviour. Prevalence rates of *Externalizing* problems ranged from 4.9 % (fathers) to 9.7 % (caregivers) in the borderline range. Across informants, 6 - 9% of the children met the criterion of the clinical range. For externalizing syndrome scales, marginally higher rates of aggressive behaviour (4 - 5% clinically relevant) than attention problems were found. In summary, the results indicate higher prevalence rates on internalizing than externalizing problem behaviour across informants. For *Total Problems*, rates varied from 6.9 % (mothers) to 10.8 % (caregivers) in the borderline range. For the clinical range, 5.8 % (fathers) to 11.0 % (caregivers) of the children met the criterion. Overall, total problems were more frequently indicated by caregivers compared to parents.

Scales Borderline Range Clinical Range Mother Father Caregiver Mother Father Caregiver *Internalizing 12.0 7.3 8.8 12.4 11.6 12.8*  Emotionally Reactive 8.4 9.2 6.8 4.1 2.4 2.9 Anxious/Depressed 5.6 6.4 5.3 3.0 0.6 6.4 Somatic Complaints 10.1 7.3 4.0 4.3 3.1 6.4 Withdrawn 3.9 3.1 5.3 5.6 5.2 2.2 Sleep Problems 2.4 0.6 only parents 3.9 2.4 only parents *Externalizing 8.6 4.9 9.7 7.3 5.5 8.6*  Attention Problems 3.9 2.4 4.2 3.0 2.1 3.1 Aggressive Behavior 4.5 4.3 5.5 2.8 1.2 2.6 *Total Problems 6.9 7.0 10.8 10.3 5.8 11.0*  Table 1. Prevalence rates in percentage for syndrome scales and *broad-band scales*, and

For all informants, there were no significant associations between children's age and gender in terms of prevalence of problem and syndrome subscales. Odds ratios ranged between 0.99 and 1.28 and were not significant. Chi-square analysis showed that *Internalizing* problems reported by mothers were overrepresented among mothers with lower education (< 9 years) compared to those with higher education levels (35.1% vs. 26.4 and 16.9%; *χ*2 (2) = 12.31, *p* < .01). Fathers reported significantly more *Total Problems* with lower maternal

were calculated.

different informants.

**5.3 Results** 

of the study were 1) to assess the prevalence of emotional and behavioural problems from different informants in children aged 3-6 years old, and 2) to investigate factors which may be associated with prevalence such as demographic and socio-economic factors.
