Evaluation of a screening algorithm using the Strengths and Difficulties Questionnaire to identify children with mental health problems: A five-year register-based follow-up on school performance and healthcare use

Background Treatment of mental health problems (MHP) is often delayed or absent due to the lack of systematic detection and early intervention. This study evaluates the potential of a new screening algorithm to identify children with MHP. Methods The study population comprises 2,015 children from the Copenhagen Child Cohort 2000 whose mental health was assessed at age 11–12 years and who had no prior use of specialised mental health services. A new algorithm based on the Strengths and Difficulties Questionnaire (SDQ) is utilised to identify MHP by combining parent-reported scores of emotional and behavioural problems and functional impairments. The screening is done on historical data, implying that neither parents, teachers nor health care professionals received any feedback on the screening status. The screening status and results of an IQ-test were linked to individual-level data from national registries. These national registers include records of each child’s school performance at the end of compulsory schooling, their health care utilisation, as well as their parents’ socio-economic status and health care utilisation. Results 10% of the children screen positive for MHP. The children with MHP achieve a significantly lower Grade Point Average on their exams, independently of their IQ-score, perinatal factors and parental characteristics. On average, the children with MHP also carry higher health care costs over a five-year follow-up period. The higher health care costs are only attributed to 23% of these children, while the remaining children with MHP also show poorer school performance but receive no additional health care. Conclusions The results demonstrate that children with MHP and a poor prognosis can be identified by the use of the brief standardised questionnaire SDQ combined with a screening algorithm.

Thank you for the comment. Our reference is a 2019 systematic review, it therefore covers existing studies evaluating different screening programs. To clarify, we added the following red text to the manuscript: Thank you for the suggestion. All variables are defined in the methods section. To clarify, we added the following red text to the manuscript: Line 87-88: The methods section provides the precise definitions of the potential confounders. Thank you for the suggestion. To clarify, we added the following red text to the manuscript: Line 152-153: Thus, we do not distinguish between different levels of MHP in this study.

Comment 6: p447. Maybe table 9 could be deleted and insert all the information of this table in a paragraph, directly in the text.
Thank you for the suggestion. We have deleted table 9 and added the following red text to the manuscript: Line 456-461: The results include the 44 children with mental health problems and minimum one contact with SMHC. We find that the mean number of days between the parents' completion of SDQ and their children's first contact with SMHC was 945 days, and the median was 1,000 days. The 25% and 75% percentiles were 426 days and 1,311 days, respectively. Thus, the results show that… Comment 7:

p463. Could you think about insert other international results in the discussion, in order to compare you results with other international papers or find a possible explanation? Maybe it would improve the paper. There is no one reference in discussion and conclusions. Please consider it.
Thank you for the comment. To address this comment, we added the following red text to the manuscript: Line 483-483: This finding is in line with previous studies that have found an association between SDQ scores and school outcomes [21,22]. The results indicate…. Thank you for the comment. Following the comment, we have re-reviewed the literature including the suggested references. We have chosen to include those references that we believe have direct relevance to the paper.
As mentioned in the response to reviewer #1 1e have added the following the following seven references to the introduction and methods section in the manuscript:

In the results section, it is not clear to me why the authors say that: "To investigate whether this subgroup of children with MHP have an unmet need for care, we use the children's later school performance as an indicator of the consequences of their MHP at the age of 11-12 years". In my opinion, this should be at least explained in the introduction. Is it there more literature confirming that a decrease in school performance can be used as an indicator of a increase in mental health problems
Thank you for the comment. The aim of this section of the paper was to clarify that also the children who screen positive for MHP, but do not receive mental health care, may be affected by MHP. As studies find that school performance is an important proxy for future life prospects (21-23), we use school performance as a potential indicator of consequences of MHP. To clarify that the comparison is not between the two groups of children that screen positive for MHP, but between children that screen negative for MHP and children that screen positive for MHPs and do not receive mental health care, we added the following red text to the manuscript: Line 406-408: Thus, finding a negative association between having MHP without receiving SMHC and later school performance, compared to children with no MHP, will indicate that there is an unmet need for care.
In addition, the following text in the background section (line 91-96) explains the choice of school performance as outcome: The children's later school performance is investigated as a primary indicator of the long-term outcome of the screening for MHP in preadolescence. As previous studies find an association between children's MHP and their school performance [20][21][22], and school performance and schooling are known to be comprehensive predictors for the rest of a child's life with respect to both wealth, health, and happiness [23][24][25], this indicator is well-suited for the evaluation of the screening.

Comment 3: In the discussion section authors state that: "The 77.3% of children with MHP who do not receive any SMHC during the follow-up period also obtain a statistically significantly worse GPA at their 9th grade exams than children with no MHP." I do not clearly understand if the comparison should be between those who have MHP and those without MHP. It is not clear if the difference is because the lack of intervention or because of the fact that they have MHP. Authors explain this, but it seems obvious, so do not really see the point of including this.
Thank you for the comment. The reason for describing the above is to highlight that, in comparison to children with no health problems, the majority of the children with mental health problems (the 77.3% who test positive for MHP but do not receive specialized care) have worse school outcome. This result suggests that it is not only the 22.7% that at some point receive specialized mental health care, who could potentially benefit from an early intervention. This result is described in line 487-488 in the manuscript.