Three-year latent class trajectories of attention-deficit/hyperactivity disorder (ADHD) symptoms in a clinical sample not selected for ADHD

Abstract

Objective: This study aims to examine trajectories of attention-deficit/hyperactivity disorder (ADHD) symptoms in the Longitudinal Assessment of Manic Symptoms (LAMS) sample.

Method: The LAMS study assessed 684 children aged 6 to 12 years with the Kiddie-Schedule for Affective Disorders and Schizophrenia (K-SADS) and rating scales semi-annually for 3 years. Although they were selected for elevated manic symptoms, 526 children had baseline ADHD diagnoses. With growth mixture modeling (GMM), we separately analyzed inattentive and hyperactive/impulsive symptoms, covarying baseline age. Multiple standard methods determined optimal fit. The χ(2) and Kruskal-Wallis analysis of variance compared resulting latent classes/trajectories on clinical characteristics and medication.

Results: Three latent class trajectories best described inattentive symptoms, and 4 classes best described hyperactive/impulsive symptoms. Inattentive trajectories maintained their relative position over time. Hyperactive/impulsive symptoms had 2 consistent trajectories (least and most severe). A third trajectory (4.5%) started mild, then escalated; and a fourth (14%) started severe but improved dramatically. The improving trajectory was associated with the highest rate of ADHD and lowest rate of bipolar diagnoses. Three-fourths of the mildest inattention class were also in the mildest hyperactive/impulsive class; 72% of the severest inattentive class were in the severest hyperactive/impulsive class, but the severest inattention class also included 62% of the improving hyperactive-impulsive class.

Conclusion: An ADHD rather than bipolar diagnosis prognosticates a better course of hyperactive/impulsive, but not inattentive, symptoms. High overlap of relative severity between inattention and hyperactivity/impulsivity confirms the link between these symptom clusters. Hyperactive/impulsive symptoms wane more over time. Group means are insufficient to understand individual ADHD prognosis. A small subgroup deteriorates over time in hyperactivity/impulsivity and needs better treatments than currently provided.

Keywords: ADHD; GMM; hyperactivity/impulsivity; inattention; longitudinal symptoms.

Figure 1

Growth mixture model latent classes of attention-deficit/hyperactivity disorder (ADHD) symptom trajectories in the Longitudinal Assessment of Manic Symptoms (LAMS) sample, not selected for ADHD, but with 526/684 having ADHD. Panel A = inattention; panel B = hyperactivity/impulsivity. NS = not significant. Panel A. Inattention latent class trajectories over 3 years. Inattention Class 1 (blue, 14.8% of sample) and Class 3 (green, 47.5%) have significant linear (slope, p = 0.004 and 0.001) and quadratic (curvature, p = 0.004 and 0.001) terms for time. Class 2 (red, 37.7%) has neither significant slope nor curvature. Panel B. Hyperactive/impulsive latent class symptom trajectories over 3 years. Class 1 (blue) = 38.5%; Class 2 (red) = 4.5%; Class 3 (green) = 43%; Class 4 (purple) = 13.9%. Classes 3 and 4 have both significant decreasing linear (slope, [p = 0.013 and 0.005]) and quadratic (curvature, p = 0.044 and 0.033) terms. Class 2 shows a significant increasing linear slope (0.12, p = 0.049) without significant curvature. Class 1 has no significant time terms.