Commonalities in social and non-social cognitive impairments in adults with autism spectrum disorder and schizophrenia

Abstract

Autism spectrum disorder (ASD) and schizophrenia are both conditions that are characterized by impairments in social and non-social cognition, yet commonalities in the magnitude and domains of cognitive deficits across these two conditions remain unclear. This study examined neurocognitive and social-cognitive functioning in 47 outpatients with schizophrenia, 43 verbal adults with ASD, and 24 healthy volunteers. A comprehensive neuropsychological battery assessing processing speed, attention, memory, and problem-solving domains was administered along with a social-cognitive battery of emotion processing. Results demonstrated large and significant impairments in emotion processing and neurocognition relative to healthy individuals in participants with autism (d = − .97 and − 1.71, respectively) and schizophrenia (d = − .65 and − 1.48, respectively). No significant differences were observed between those with ASD and schizophrenia on any cognitive domain assessed, and the areas of greatest impairment were identical across both disorders and included slowness in speed of processing and an inability to understand emotions. These findings indicate a high degree of similarity in the cognitive challenges experienced by verbal adults with autism and schizophrenia, and the potential need for trans-diagnostic remediation approaches to enhance cognition in these conditions.

Introduction

Autism spectrum disorder (ASD) and schizophrenia are severe neurodevelopmental disorders that are both characterized by considerable impairments in social and emotional function and information processing (Lewis and Levitt, 2002, Volkmar et al., 2004). The earliest definitions of schizophrenia considered autism to be a childhood form of the illness, in part due to the gross cognitive and functional impairments observed in the two disorders (Bleuler, 1911). Although subsequent clinical evidence delineated unique aspects of the two conditions (Kanner, 1965), the notion that ASD and schizophrenia share some important commonalities in phenomenology (Couture et al., 2010), pathophysiology (Guilmatre et al., 2009, Pinkham et al., 2007, Sugranyes et al., 2011), and treatment (McCracken et al., 2002) has remained long after their distinction in modern psychiatric nosology.

Impairments in information processing, particularly social information processing, are some of the deficits most commonly noted to be shared between ASD and schizophrenia (e.g., Sugranyes et al., 2011). While many studies have demonstrated impairments in social domains within autism and schizophrenia samples (Baron-Cohen et al., 1985, Penn et al., 1997, Heinrichs and Zakzanis, 1998, Ozonoff et al., 2004), few studies have compared the domains and magnitude of cognitive impairment between these conditions. Early work by Schneider and Asarnow (1987) examined 11 individuals with childhood schizophrenia and 15 lower functioning children with autism, and found similar levels of impairment in processing speed and executive function. Another study found that a sample of 31 verbal adults with ASD had similar degrees of processing speed and comprehension as a psychometrically defined subsample of high-functioning inpatients with schizophrenia (Goldstein et al., 2002). With regard to social cognition, Pilowsky et al. (2000) identified similar theory of mind impairments in 12 individuals with childhood onset schizophrenia and 12 children with autism relative to healthy controls. Sasson et al. (2007) also found comparable levels of slowing in gaze orientation toward social stimuli among 10 adults with schizophrenia and 10 adults with autism, although the autism group demonstrated a differential slower speed of orienting toward emotional faces. Conversely, some have found greater impairments in facial emotion perception in children with autism compared to schizophrenia (Bolte and Poustka, 2003), and other studies have found impairments in this domain to be similar among adults with these two conditions (Couture et al., 2010). Several studies have also found overlap in the neurobiologic deficits present in ASD and schizophrenia, particularly with regard to functional abnormalities associated with social-cognitive impairment (Pinkham et al., 2007, Sugranyes et al., 2011).

Although there is growing evidence of meaningful overlap in social and non-social impairments among individuals with ASD and schizophrenia, these studies have mostly been characterized by small sample sizes, particularly in the patient groups, which may have precluded detecting differences in cognitive impairment across these disorders, and few studies have used rigorous methods for diagnosing ASD and schizophrenia. Furthermore, comparative studies focusing on differences in non-social cognitive impairment in higher functioning verbal adults with autism, who may be less cognitively disabled, have not been conducted. This study sought to examine neurocognitive impairments and social-cognitive deficits in emotion processing in rigorously diagnosed and well-characterized samples of verbal adults with autism and adults with schizophrenia compared to healthy individuals, in an effort to identify similarities and differences in cognitive function that could demonstrate a need for shared and/or unique approaches to the treatment of cognition in these populations.