Autism and schizophrenia: neurodevelopmental ‘playmates’?

Chapter 4 Autism and schizophrenia: neurodevelopmental ‘playmates’?

KEY POINTS

• Historical constructions of schizophrenia encompassed autism within their core.

• Autism and schizophrenia share certain neurodevelopmental markers, but the emphasis in autism is on reduced social awareness, restricted interests and verbal delay.

• Certain neurobiological findings overlap between autism and schizophrenia, albeit the former group tends to have larger brain volumes, whilst the latter have volume reductions in key brain areas.

• The emphases of treatment between autism and schizophrenia diverge, with the use of techniques to enhance socialization, deal with impairing behaviours, and enhance language skills being more front-and-centre in autism than schizophrenia.

To the lay public, schizophrenia and autism appear ‘poles apart’. In the movie A Beautiful Mind, actor Russell Crowe plays the mathematics genius John Nash whose delusions, hallucinations, and resultant aberrant behaviours undermine his capacity to function. This movie well describes the features and course of schizophrenia. Similarly, the movie Rain Man provides a ‘textbook account’ of autism. In this movie, Dustin Hoffman typifies the social and verbal restrictions of autism, the idiosyncratic heightened interest/focus/skill in selective area(s), and the gross motor abnormalities of autism. A recent study of the lay public opinions of various mental illnesses confirms that people are discerning about these conditions and understanding thereupon (Butlin et al. 2019). Gratifyingly, the field of autism research has dramatically expanded over the last decade and there is a much greater understanding of both biological and psychosocial aspects of autism (Bhandari et al. 2020; Lord et al. 2020). This chapter accordingly focuses selectively on aspects of overlap between autism and schizophrenia, reflecting upon contemporary perspectives on each condition (Lord et al. 2020; McCutcheon et al. 2020; Zheng et al. 2018).

Autism and schizophrenia: historical antecedents and rates of co-occurrence

It is perhaps surprising to consider that autism and schizophrenia were at one time viewed as similar conditions. Although Euger Bleuler’s use of the term ‘autism’ was not synonymous with the modern-day word, Bleuler considered autism (infantile, dream-like withdrawal) as a fundamental feature of schizophrenia. And when autism was first described in a case series by Leo Kanner in 1923 it was referred to as ‘Kanner’s psychosis’. Subsequent descriptions by other leading child psychiatrists, foremost among them the British psychiatrist Sir Michael Rutter, clarified that the features of autism were largely different from schizophrenia and that there was a reliability of presentation and course to be able to describe autism as a distinct condition. As described in the Diagnostic and Statistical Manual of Mental Diseases, Fifth Edition (DSM-5, 2013), the core features of autism are across several domains and still do show some potential for overlap with schizophrenia (Box 4.1).

Box 4.1 Diagnostic features of autism—all longstanding and not attributable to mental retardation or other causes of developmental delays

• Restricted emotional valence

• Restricted verbal and ‘body language’ output

• Restricted social awareness and impoverished ‘social cues’

• Tendency towards intense interest and/or activities focused in a particular area

In some contrast to schizophrenia, social withdrawal predominates in autism (Leong and Schilbach 2019). Also, clearly delineated delusions or hallucinations are uncommon in autism (Chandrasekhar et al. 2020). Moreover, there is substantial overlap and comorbidity between autism and other psychiatric conditions beyond schizophrenia (Jokiranta-Olkoniemi et al. 2019; Stralin et al. 2019).

Presently, there is mixed information as to whether—and how often—autism and schizophrenia co-occur, given symptom overlap, particularly in very young children (Chandrasekhar et al. 2020). De Giorgi and colleagues (2019) conducted a systematic review of the prevalence of schizophrenia (they used the term ‘non-affective psychosis’) in autism. In broadening the criteria to include autism spectrum disorder (ASD), they identified 39 articles describing the overlap between the two conditions. On a more refined evaluation of 14 of these articles that encompassed some 1,700 patients, they arrived at a weighted average prevalence rate of psychosis among autistic individuals of 9.5%. This is clearly above the rate of schizophrenia in the general population, yet it is not so high as other conditions (e.g. depression, OCD) associated with schizophrenia.