In research involving children, there is general agreement on the importance of early discovery of and early interventions towards mental health problems. For this to be possible, we need instruments with proper psychometric qualities. One of the most commonly used instruments for assessing behaviour and mental health problems among younger children is the Strengths and Difficulties Questionnaire (SDQ), which is being used both clinically and in research on children aged 2–17 (http://www.sdqinfo.com
). Consisting of 25 items, the SDQ is a relatively short questionnaire while still being comparable to the similar but lengthier Child Behavior Checklist (CBCL), displaying moderate to high correlations on total and equivalent subgroup scores [1
]. The SDQ, in general, displays good construct and concurrent validity, as well as some evidence on predictive validity [3
]. Construct validity has mainly been assessed using confirmatory factor analysis (CFA). Although displaying promising psychometric properties, few studies have investigated the SDQs validity and reliability for use among preschool-aged children specifically (see Croft et al. [6
] for one example); on the contrary, it has mostly been used with teenagers or a broad range of ages spanning through preschool and the early school years. A study by Croft et al. [6
] concluded satisfactory construct validity for preschool children when rated by parents.
Factor analytic studies of the SDQ have supported the original five-factor structure in many [7
] but not all cases [5
]. In a large sample study, Goodman et al. [13
] concluded that the five-factor model should be used in clinical samples, while a model with two broader externalising and internalising subscales should be used in epidemiological studies or low-risk samples. Stone et al. [3
] found support for the original factor solution, when analysing data from several previous studies. To the best of our knowledge, the major part of the CFA studies published concern school children. Thus, we identified a need for more studies on the construct validity of the SDQ for preschool children. Ezpeleta et al. [14
] have provided some evidence suggesting that the original five-factor model is feasible for preschool children, although not entirely convincing mainly due to low values on indices of comparative fit. Investigating factor structure of the SDQ for pre-schoolers in a Nordic context, support for a two-factor model consisting of hyperactivity and conduct problems was found for children aged 1–3, while a model including the original subscales, except for the prosocial subscale, was proposed for 4–5-year-olds [15
The multi-informant approach of the SDQ provides opportunity to assess the validity of the questionnaire when filled in by different informant groups. Data from teachers’ ratings generally show better model fit than parents, especially on subscale level [3
]. Although there is evidence for good validity of teachers’ SDQ ratings of children in primary school [16
], no CFA studies have included preschool teachers.
Some studies of the SDQ have indicated that fathers tend to report more externalising behaviour problems than mothers [17
]. Interestingly, fathers are rarely treated as a unique informant group in validity studies of the SDQ. In the published CFA studies that we found, separate analyses of mothers and fathers are conspicuous by their absence, with very few exceptions (e.g. [19
]). Looking at how parent data are constituted, mothers are greatly overrepresented, with fathers mostly present as either co-respondents or marginally represented together with the mothers (e.g. [14
]). It is also common to report parents as one group, not specifying the proportions of mothers and fathers (e.g. [16
]). Although it can be argued that the factor structure of the SDQ rated by fathers and mothers should be similar—a statement somewhat supported by Björnsdotter et al. [19
]—this is something that needs to be empirically investigated further in order to answer questions regarding the validity of SDQ across different informants and age groups.
For preschool children, measurement invariance has been established between mothers and fathers [22
]. Still, to the best of our knowledge, the only studies assessing invariance across different age groups, child gender, or parental (maternal) education level within each informant group are on school-aged children [23
The aim of the present study is to test the original five-factor structure of the SDQ for preschool children and to assess whether the suggested model has an acceptable fit for fathers as well as mothers and preschool teachers. This study also seeks to assess measurement invariance across child gender, child age, and parental education for all three informant groups.
The purpose of this study was to investigate the factor structure of the SDQ for fathers, mothers and preschool teachers in a community sample, as well as to assess measurement invariance across child gender, child age, and parental education level. Our study adds to the psychometric literature on the SDQ and specifically increases knowledge about the construct validity of the SDQ when rating pre-schoolers. Previous research has mainly focused on school-aged children and adolescents and rarely on preschool children only, making our study a new and valuable contribution to knowledge on the SDQ for this age group by thoroughly assessing the factor structure across different informants and confirming MI. Our findings show that the original five-factor model of the SDQ can indeed be used on younger children in a general child population, also indicating its reliability in the hands of different informants.
This is the first time that data from fathers have been analysed separately through CFA when assessing the construct validity of the SDQ for pre-schoolers, and the second time for all ages [19
]. Fathers are increasingly involved in and important for the child’s development and can provide very useful information about the child [38
]. Still, psychometric properties of questionnaires like the SDQ that measure children’s behaviour and emotional problems have seldom been investigated for fathers. To secure gender equality at child health services concerning involvement of both parents, it is essential to use instruments that are validated for fathers as well as mothers.
In addition, preschool teachers as informants have not been thoroughly assessed before, making this study an important contribution to aggregated knowledge on the SDQ. It is also an important step towards gathering reliable information from multiple sources when assessing children’s mental health, as recommended by Goodman et al. [4
]. In a study by Fält et al. [40
], the child health nurses reported that the quality of health check-ups for 3–5-year-olds improved when they had SDQ ratings from the preschool teacher as well as from the parents. The present study adds to the knowledge on the SDQ as a valuable tool for screening for mental illness in children by assessing its construct validity when used on preschool children. Since 95% of all preschool children in Sweden visit child health centres regularly [26
] and attend preschool, using the SDQ as the standard procedure in this setting could be one way of reaching children at risk at an early stage.
The invariance analyses suggest that both metric and scalar invariances are present for all informants, across child gender, child age, and education levels of the parents. MI has only been established across different countries [41
] and informant groups [22
]. Although Stone et al. [23
] provide some evidence for metric invariance across child gender and maternal education level for mothers rating school children, the cut-offs that they used for acceptable fit were more liberal than generally recommended. Our study shows metric invariance according to more conservative standards.
The results from our study confirm the five-factor structure for the Swedish version of the SDQ, thus being in line with previous studies suggesting that the SDQ is comparable across cultures [21
]. The results also indicate that cultural modification of the SDQ, in terms of an altered wording of three items, based on preschool organisational preferences, did not jeopardise the model fit.
Although the factor structure was acceptable for mothers, fathers and preschool teachers alike, we were not able to test for MI across informants. This was due to the fact that many children in the current sample were rated by more than one informant. Thus, clustering effects were likely to occur in a random fashion, for which we were not able to control. Therefore, we decided to analyse the data from the three informants separately, resulting in as much data as possible and not introducing possible confounders by removing children not rated by all informants. Comparison of fitness between informants was therefore not possible, which can be seen as a limitation.
The sample in our study included a larger proportion of people with higher education compared to the distribution within the municipality. Although we cannot completely eliminate the possibility that the slightly lopsided sample in terms of parental education level could affect the factor structure, MI across the education variable suggests that the SDQ is a valid instrument across different parental education levels.
As the SDQ shows satisfactory construct validity, it would be desirable to present norms for this age group and for all three informants in a future study. In fact, to facilitate the application of the SDQ in clinical settings, it is necessary to provide norms from a large community sample, covering children aged 3–5 and all three informants. Finally, although we found the construct validity to be good in the present study, we did not analyse any competing theoretical models of the factor structure of the SDQ. It is possible that another theoretical model would provide even better fit, such as the four-factor multi-trait-multi-method structure suggested by Bull et al. [43
]. However, since the original model is the one being used in clinical practice and the only model provided with norms, we chose to analyse this model only.
Notwithstanding the above-mentioned limitations, the results from our study imply that the SDQ is a feasible instrument for assessing emotional and behavioural problems among preschool children. Moreover, our study is an important step in investigating whether the original five-factor structure of the SDQ can be used in large community samples. Findings based on fathers’ ratings suggest acceptable fit, implying that the SDQ rated by fathers can be used to the same extent as mothers’ ratings to assess behaviour problems among preschool children.
Lastly, the sample in this study was a non-clinical sample, which allowed for assessment of the construct validity of the instrument when used on the general population. Factor analytic studies from the lengthier but comparable CBCL for preschool children indicate good fit when rated by parents or preschool teachers in clinical and non-clinical samples in most but not all studies [44
]. However, CFAs assessing fathers’ ratings have not examined the questionnaire on subscale-level [48
]. Our findings suggest that the SDQ might be a suitable instrument for epidemiological studies of preschool children’s mental health and can be used in its originally proposed five-factor solution in non-clinical populations. This enables thorough investigation of subscale differences in epidemiological studies, thus resulting in more detailed studies of populations.
The SDQ is a well-established instrument for measuring social and behavioural problems among children, with good psychometric properties for older children, but less validity reports on pre-schoolers. In addition, there is a knowledge gap concerning fathers as informants. The present work is one of the few validity studies to include preschool teachers and the first on preschool children, where fathers are included as separate informants. In this study, the SDQ was collected from a large community sample (n = 17,752) of children aged 3–5, rated by mothers, fathers, and preschool teachers and analysed using alpha calculations and confirmatory factor analysis. Measurement invariance analyses were also conducted to assess invariance across child gender, child age, and parental education level. Our results revealed high internal consistency, acceptable fit for all informant groups and measurement invariance across child gender, child age, and parental education level. Our findings suggest good construct validity of the SDQ for a non-clinical preschool population and imply that it may be used for assessing behaviour problems in pre-schoolers from different informant perspectives.