Maternal ratings of attention problems in ADHD: evidence for the existence of a continuum.

OBJECTIVE To investigate whether items assessing attention problems provide evidence of quantitative differences or categorically distinct subtypes of attention problems (APs) and to investigate the relation of empirically derived latent classes to DSM-IV diagnoses of subtypes of attention-deficit/hyperactivity disorder (ADHD), for example, combined subtype, predominantly inattentive type, and predominantly hyperactive/impulsive type. METHOD Data on attention problems were obtained from maternal ratings on the Child Behavior Check List (CBCL). Latent class models, which assume categorically different subtypes, and factor mixture models, which permit severity differences, are fitted to data obtained from Dutch boys at age 7 (N = 8,079), 10 (N = 5,278), and 12 years (N = 3,139). The fit of the different models to the data is compared to decide which model, and hence, which corresponding interpretation of AP, is most appropriate. Next, ADHD diagnoses are regressed on latent class membership in a subsample of children. RESULTS At all the three ages, models that distinguish between three mainly quantitatively different classes (e.g., mild, moderate, and severe attention problems) provide the best fit to the data. Within each class, the CBCL items measure three correlated continuous factors that can be interpreted in terms of hyperactivity/impulsivity, inattentiveness/dreaminess, and nervous behavior. The AP severe class contains all of the subjects diagnosed with ADHD-combined subtype. Some subjects diagnosed with ADHD-predominantly inattentive type are in the moderate AP class. CONCLUSIONS Factor mixture analyses provide evidence that the CBCL AP syndrome varies along a severity continuum of mild to moderate to severe attention problems. Children affected with ADHD are at the extreme of the continuum. These data are important for clinicians, research scholars, and the framers of the DSM-V as they provide evidence that ADHD diagnoses exist on a continuum rather than as discrete categories.