To our knowledge, this is the first study to examine the stability of specific psychiatric disorders in a large community sample of preschoolers using a comprehensive diagnostic interview and a prospective longitudinal design. At both the age 3 and age 6 assessments, approximately a quarter of the sample met criteria for a diagnosis within the previous 3 months. The overall rate of disorders did not change over this period. Half the children who met criteria for a diagnosis at age 3 again met criteria for a diagnosis at age 6, and about half the children who met criteria for a diagnosis at age 6 had met criteria for a diagnosis at age 3. Overall, children who met criteria for a diagnosis at age 3 were nearly five times as likely as other children to meet criteria for a diagnosis again at age 6.
Previous studies have reported that substantial numbers of preschoolers meet criteria for a psychiatric diagnosis (1
). Our findings here indicate that many of these children continue to exhibit psychopathology 3 years later, which supports the validity of Preschool Age Psychiatric Assessment DSM-IV diagnoses in preschoolers and indicates that for many children these are not transient problems that are rapidly outgrown. However, this does not preclude the possibility that some of our cases were false positives exhibiting developmentally normative levels of particular behaviors; more work is needed to determine the threshold between normal and pathological behavior in early childhood (11
). In other cases, there may be personal or environmental factors that promote recovery in preschoolers with psychiatric disorders. We plan to examine this issue in future analyses. Finally, these results cannot be generalized to other classification systems. The organization Zero to Three has an alternative diagnostic system for young children (32
), but few data are available on its reliability and validity (9
Although the rates of most disorders were similar at ages 3 and 6, there was a significant increase in rates of depression and ADHD and a decrease in generalized anxiety disorder. Previous research suggests that depression is diagnosed more often in older rather than younger preschool-age children (8
). The increase in the rate of depression may reflect children’s growing ability to vocalize distress, which would raise parents’ awareness of these symptoms. This increase may also reflect an actual change in the rate of depression as children transition to school age, when they face increasing performance demands and develop a growing tendency to compare themselves with others, perhaps less favorably (33
). The increase in rates of ADHD is consistent with other research (34
) and may reflect the fact that symptoms are more impairing and easier to recognize as children enter formal schooling, requiring them to function in increasingly demanding social and academic contexts and maintain greater control over their behavior. The reason for the decrease in the rate of generalized anxiety disorder is less clear, and there are few data on this condition in preschoolers to elucidate it (35
). It is possible that the developmentally normative inquisitive nature of younger children (36
) is perceived as worrying by some parents. The importance of studying worry in young children (3
) is underscored by this unexpected finding.
There was significant homotypic continuity between age 3 and age 6 for anxiety disorders, ADHD, and oppositional defiant disorder, as well as for five of the six individual anxiety disorders. Little research has been conducted on the stability of a broad range of specific disorders assessed with a diagnostic interview in community samples of preschoolers, and there are no comparable data on the stability of individual preschool anxiety disorders. Similar to our findings, other studies have reported that preschoolers with ADHD (14
) and oppositional defiant disorder (13
) are likely to continue to meet criteria for these disorders into school age, although the degree of continuity varied across these few studies. One study reported significant homotypic continuity for pre-school depression (20
) in the context of a case-control design. Although we did not observe homotypic continuity of depression, too few children had depression diagnoses at age 3 to examine this question in a meaningful fashion.
We found heterotypic continuity between depression and anxiety, anxiety and oppositional defiant disorder, and ADHD and oppositional defiant disorder. The magnitudes of the odds ratios were largely similar across homotypic and heterotypic analyses (although caution is warranted in making comparisons, given the large standard errors), suggesting that there is both stability and change in diagnostic status over time. Depression and anxiety disorders at age 3 each predicted the other at age 6, which is consistent with findings in school-age children, adolescents, and adults (37
). In addition, ADHD and oppositional defiant disorder at age 3 each predicted the other disorder at age 6. However, results were attenuated somewhat when we controlled for concurrent age 3 comorbidity. Age 3 agoraphobia was associated with multiple age 6 diagnoses: depression, specific phobia, social phobia, generalized anxiety disorder, and selective mutism. Although the meaning of agoraphobia in early childhood is unclear, these findings warrant further investigation. The observed heterotypic pathways may reflect causal effects, shared risk factors, or different expressions of similar processes (39
); these results point to the importance of a better understanding of changing phenotypes across development (11
While homotypic continuity is central to the classic Robins and Guze (12
) framework for validating psychiatric diagnoses, the role of heterotypic continuity is more ambiguous. If it is viewed as one disorder changing into a distinctly different disorder, it would indicate poor validity. However, if heterotypic continuity represents two phases or alternative presentations of a single disorder, as is often assumed, this supports validity, albeit for a broader diagnostic construct. Unfortunately, it is difficult to distinguish between these scenarios without a firm understanding of the underlying processes.
We are aware of only one longitudinal study that assessed psychiatric disorders in a large sample of preschool-age children from ages 2–5 to age 7 (19
). Similar to our findings, that study reported moderate diagnostic stability, which was greater for externalizing disorders than for emotional disorders. However, structured diagnostic interviews were not used, and only broad diagnostic categories (i.e., emotional, disruptive, and other disorders) were examined.
In evaluating these results, a number of limitations should be considered. First, although retention was relatively high, almost 15% of the children assessed at age 3 could not be assessed at age 6. However, there were few differences between participants and dropouts, suggesting that any bias due to attrition is likely to be small. Second, interviews with parents were conducted by telephone for the age 3 assessment and face-to-face for the age 6 assessment. However, diagnostic interviews with parents regarding their children have yielded equivalent results when administered by telephone and face-to-face (30
). Third, we used a screen for ADHD and oppositional defiant disorder to reduce administration time for the first 60% of the sample in the age 3 assessment. However, given the interviewers’ confirmation of negative screens, the false negative rate was probably quite low. In addition, results were comparable for the two parts of the sample. Fourth, diagnoses were based on interviews with one parent. Incorporating data from other sources (e.g., a second caretaker, observation of the child) and confirmation of diagnoses by an experienced child psychiatrist or psychologist would provide a more comprehensive assessment and minimize biases associated with a single informant. Fifth, given the small number of cases of major depression or dysthymia, depression not otherwise specified was included in the “any depression” group, which may have increased the heterogeneity of this category. Sixth, the 3-month primary period may have limited our ability to identify cases with onset and remission occurring prior to this period or between assessments. This issue may be particularly problematic for episodic disorders such as depression. Seventh, the use of audiotapes to assess interrater reliability produced high-end estimates compared with independent interviews. Eighth, for some of the continuity analyses, the confidence intervals were relatively large. Finally, the sample was largely white and middle-class. Although this mirrored the demographic characteristics of the area, the stability of preschool psychiatric disorders should be examined in more diverse samples. Indeed, disorders may be more persistent in environments characterized by high levels of stress and adversity (40
In summary, this is the first study to examine the stability of a wide range of specific psychiatric disorders in a large community sample of preschoolers using a comprehensive diagnostic interview and a prospective longitudinal design. We found that Preschool Age Psychiatric Assessment DSM-IV diagnoses were moderately stable and that children with a diagnosis at age 3 had a fivefold greater risk of meeting criteria for a diagnosis at age 6. These data support the validity of preschool psychiatric diagnoses and underscore the importance of early identification and intervention in preschoolers to prevent chronicity and recurrence.