Objectives: We have conducted the first study to examine the longitudinal pattern of association between social-communication deficits and hyperactive-inattentive symptoms in the general population, from childhood through adolescence. We explored the interrelationship between trajectories of co-occurring symptoms, and sought evidence for shared prenatal/perinatal risk factors.
Methods: Study participants were 5,383 singletons of white ethnicity from the Avon Longitudinal Study of Parents and Children (ALSPAC). Multiple measurements of hyperactive-inattentive traits (Strengths and Difficulties Questionnaire) and autistic social-communication impairment (Social Communication Disorder Checklist) were obtained between 4 and 17 years. Both traits and their trajectories were modeled in parallel using latent class growth analysis (LCGA). Trajectory membership was subsequently investigated with respect to prenatal/perinatal risk factors.
Results: Our longitudinal approach to data analysis over a 14 year period of follow-up identified two social-communication domain related autistic trait trajectories (persistently impaired versus low-risk) and four hyperactive-inattentive trait trajectories (persistently impaired, intermediate, childhood-limited, and low-risk). Our findings are consistent with earlier reports of high stability of autistic symptoms, and with evidence for a greater variability of ADHD-like behaviour, during the course of child development from 4 to 17 years. Among the hyperactive-inattentive trajectories, the observation that there are both persistently-impaired and childhood-limited patterns matched previous reports indicating subgroups with stable ADHD symptoms and others showing a decline of ADHD symptoms with progressing age, respectively. We found that the observed trait interrelationship between the most persistently impaired individuals is not reciprocal. Although the majority of children with persistently impaired social communication skills were either part of the persistently impaired hyperactive-inattentive or the intermediate hyperactive-inattentive group, children with persistent hyperactive-inattentive symptoms were almost entirely subsumed within the persistently impaired social-communication group.
Conclusions: The strong trajectory links observed in our study, especially between the most persistently affected individuals, directly support the proposed revisions for DSM-5. These include changes with respect to separate recording of ADHD criteria and of ASD symptoms, which will allow ASD and ADHD to be diagnosed in the same individual. We propose the possible existence of a novel autistic/hyperactive-inattentive syndrome. Our hypothesis finds general support through recently published genetic analyses, including both general population traits and genetic studies of individuals with severe symptoms. Recent research suggests common genetic variants, identified from ADHD and ASD genome-wide association analysis, may increase predisposition to both conditions.