Five-Year Follow-up of Preschoolers with Autism and Comorbid Psychiatric Disorders.

* Recent evidence on children with autism spectrum disorders (ASD) has confirmed not only steep increases in identification of children with the disorder but also wide variability within the spectrum itself, as well as large disparities in diagnostic eligibility and access to care (Chakrabarti & Fombonne, 2005; Kuehn, 2012; Morder & Hess, 2012). Such heterogeneity has led to an interest in studying possible comorbid psychiatric disorders of children with ASD, with large population-derived studies suggesting considerable overlap between core symptoms of autism and those of other psychiatric disorders such as attention-deficit hyperactivity disorder (ADHD), oppositional defiant disorder or conduct disorder, depression or dysthymia, and anxiety disorders (Hallett, Ronald, & Happe, 2009; Hass, Brown, Brady, & Johnson, 2010; Simonoff et al., 2008; Skuse et al., 2009). Such comorbid conditions are thought not only to exacerbate the social, communicative, and behavioral difficulties already inherent in children with autism but also to complicate their diagnostic ascertainment and access to services (Matson & NebelSchwalm, 2007; Warren et al., 201 1).Prevalence of total comorbid psychiatric diagnoses in samples of children with ASD generally falls in the 30% to 80% range, suggesting that generally, at least a third of children in programs for ASD also have a cooccurring emotional or behavioral disorder. Studies on which these data are based vary widely in terms of sample selection, choice of diagnostic measures or informants, and types of prevalent disorders found within each study. For example, Leyfer et al. (2006) found the highest rates of anxiety disorders (37%-44%) in their sample, but other studies have found such rates only in the 20% to 30% range (Gadow, DeVincent, Pomeroy, & Azizian, 2005; Kanne, Abbacchi, & Constantino, 2009; Lecavalier, 2006). Gadow et al. (2005) found nearly half of their sample to have ADHD, whereas other studies have generally found ADHD rates to be less than one third (Kanne et al., 2009; Lecavalier, 2006; Leyfer et al., 2006). Ghaziuddin, Ghaziuddin, and Greden (2002) have found rates of depression or dysthymia in the 20% to 30% range, whereas other studies, noted above, found rates of these disorders to be generally in the 1 0% to 1 5% range. Note that higher rates of comorbidity in these studies are generally found in clinic or hospital settings, with markedly lower rates in community or school settings.Only two studies to date have focused on preschool samples. Gadow et al. (2004) studied 1 72 preschoolers (age 3 to 5 years) with ASD in a clinic sample, along with 507 in community preschools and 140 in special education preschools. Using a questionnaire for psychiatric disorder categories, they found the highest rates of comorbidity in the clinic sample at 51 % for anxiety disorders and 41% for ADHD but only small percentages (1 5% or fewer) for other disorders. In their other two preschool samples, these rates were only about half the rates found in the clinic sample. Hayashida, Anderson, Paparella, Freeman, and Forness (2010) screened a hospital day treatment sample of 1 75 preschoolers with two questionnaires. One questionnaire was the same as that used in the Gadow et al. (2004) study. On that questionnaire, they found dysthymia to be the most prevalent comorbid disorder at 51%, with depression and ADHD both about 35% and anxiety disorders about 30%. The other questionnaire generally confirmed this rank order but at somewhat lower percentages.There has, however, been relatively little serious discussion in the above literature of the "so what?" question. In other words, what are the implications, if any, for a child with autism who has a comorbid diagnosis? Do such diagnoses just represent more severe extensions of core ASD symptoms? Does ADHD, for example, just represent a more serious lack of eye contact, or does depression or dysthymia just represent a more restricted type of social interaction? …