Children evidencing high symptoms included 19% at kindergarten, 21% at grade 1, 27% at grade 3, and 16% at grade 5, with approximately equal percentages showing high externalizing and high internalizing symptoms. For all but the grade 5 assessment, there were significantly more boys with high externalizing symptoms [kindergarten to grade 3, range of X2
(1, N=328) = 3.41 to 5.70, p
s < .05; grade 5, p
= .057]; there were no gender differences in high internalizing symptoms (all p
s > .15). By grade 5, 41% of children had evidenced high symptoms at some point since kindergarten; of these children, 39% had high symptoms once, 36% twice, 15% three times, and 10% all four times. These prevalence and incidence rates are consistent with those of previous epidemiological research (Costello et al., 2003
Longitudinal Patterns of Mental Health Symptoms
The patterns of transitions in symptoms from one assessment time to the next were quite similar. Thus, highlights the average pattern.
Table 1 Average Transition Matrix from One Assessment Time to the Next, Kindergarten to Grade 5. Three matrices were defined: kindergarten to grade 1, grade 1 to grade 3, and grade 3 to grade 5. Percentages are averages of the three matrices, with those for the (more ...)
As expected, the most common transition from one assessment time to the next was from Low Symptoms to Low Symptoms (average 88%). Consequently the most common longitudinal pattern was one in which high symptoms were never seen (i.e., Never Symptoms; 58.8%).
Among children with only Internalizing or Externalizing symptoms, the most common transition was a return to Low Symptoms (average 69% of Internalizing Only and 43% of Externalizing Only). Thus the next most common pattern is one in which there are no two consecutive assessments with symptoms (i.e., Isolated Symptoms; 21.6%). In addition to those with only Internalizing or Externalizing symptoms, most children who transition from Low Symptoms to Internalizing Only will likely be in this group since the probability of transitioning from Internalizing Only to either of the other two high symptom groups is very low.
Finally, the remaining children were those with recurrent symptoms (i.e., high symptoms at consecutive assessments), with Comorbid Symptoms the most stable over time (average 42%). Thus, the remaining patterns were divided into two groups with recurrent symptoms, either without comorbid internalizing and externalizing symptoms (i.e., Recurrent Non-comorbid Symptoms; 10.1%) or with comorbid symptoms at least once (i.e., Recurrent Comorbid Symptoms; 9.5%).
Notably, children with Recurrent Comorbid Symptoms were most likely to have high symptoms at least three times (77%) and almost half had high symptoms all four times (45%). In contrast, children with Recurrent Non-comorbid Symptoms were most likely to have high symptoms only twice (70%) and none had symptoms all four times. Children with Isolated Symptoms generally had high symptoms only once (73%).
Comparisons of the longitudinal symptom groups showed that there were no statistically significant differences in child gender (χ2 [3, N=328] = 5.45, p = .142).
Grade 5 Outcomes
Overall, children with Recurrent Comorbid Symptoms had the highest levels of impairment and service use by grade 5 (). Teachers reported significantly higher levels of academic, social, and global impairment, and global physical health problems for this group compared with the other three groups. Teachers also reported the highest rates of service use for this group, with almost half (48.4%) using school-based services in grade 5. Mothers reported that, compared with the Never and Isolated Symptoms groups, children in the Recurrent Comorbid Symptoms group had higher rates of specialty mental health treatment, with over a third (36.7%) having received treatment from a psychologist or psychiatrist.
Grade 5 Outcomes of Longitudinal Symptom Groups.
Children in the Isolated and Recurrent Non-comorbid Symptoms groups also differed significantly from the Never Symptoms group, showing higher levels of academic, social, and global impairment, and higher rates of school-based service use and specialty mental health care.
There were no statistically significant gender differences in the grade 5 outcomes or the associations of the outcomes with the longitudinal symptom groups (main and interactive effects, all ps < .19).
The clinical significance of the symptom group differences in grade 5 outcomes is highlighted in . NNT comparing the Recurrent Comorbid Symptoms versus the Never Symptoms groups indicates generally strong discrimination (all NNTs ≤ 3.2), especially in Academic, Social, and Global Impairment and Specialty Mental Health Treatment [NNTs ≤ 2.3, corresponding to Cohen’s standard for a large effect size, d
> .8 (Cohen, 1988
)]. These NNT values indicate much stronger discrimination than that between the Never Symptoms group and Recurrent Non-comorbid Symptoms (NNTs = 2.0 to 9.5) or Isolated Symptoms (NNTs = 3.4 to 12.0) groups.
Figure 2 Number Needed to Take (NNT), an effect size indicating the clinical significance of differences in each grade 5 outcome between children in the Never Symptoms group (n = 193) and those in the Isolated (n = 71), Recurrent Non-comorbid (n = 33), and Recurrent (more ...)
Early Identification of Children with Recurrent Comorbid Symptoms
Children’s trajectories of mental health problems are quite evident as early as kindergarten. Kindergarteners with Low Symptoms were not likely to develop later symptoms (72% Never Symptoms). Kindergarteners with Internalizing Only symptoms were most likely to develop a pattern of Isolated Symptoms (65%), or less likely, Recurrent Non-comorbid Symptoms (30%). Kindergarteners with Externalizing Only symptoms were less likely to develop a pattern of Isolated Symptoms (39%), and most likely to develop recurrent symptoms, either Recurrent Comorbid Symptoms (32%) or Recurrent Non-comorbid Symptoms (29%). Notably, although only 10 kindergarteners evidenced Comorbid Symptoms, 100% of them developed a pattern of Recurrent Comorbid Symptoms.
Finally, an ROC analysis, as described in the Data Analysis section, was applied to identify as early in school as possible the children who developed Recurrent Comorbid Symptoms (n = 31 of 328; 9.5% base rate). The most optimal predictor identified the high-risk subgroup of 10 children with Comorbid Symptoms in kindergarten (3% of the population), described above, 100% (10/10) of whom developed Recurrent Comorbid Symptoms compared with only 6.6% (21/318) of the remaining children. Next, within the remaining subgroup of 318 children (those without comorbid symptoms in kindergarten), the most optimal predictor identified the subgroup of 29 children with externalizing symptoms in grade 1 (9% of the population), 51.7% (15/29) of whom developed the Recurrent Comorbid pattern. When both high-risk groups were considered together, 64% (25/39) developed Recurrent Comorbid Symptoms compared with only 2.1% (6/289) of the children in neither high-risk group. Moreover, this final classification correctly identified 81% (25/31) of the children who developed Recurrent Comorbid Symptoms (sensitivity) and 95% (283/297) of those who did not (specificity). (#1), compared with the sensitivity and specificity of the other classifications considered, is the most optimal based on its relative proximity to ideal and distance from random.
Figure 3 Receiver Operating Characteristic (ROC) plane using sensitivity and specificity to compare the proposed screening algorithm based on kindergarten comorbidity and grade 1 externalizing (#1) with alternatives based on kindergarten comorbidity alone (#2), (more ...)