Review on Contributing Factors to Anxiety in High-Functioning Autism

Introduction

Autism spectrum disorder (ASD) is characterized by weaknesses in social communication and interaction in multiple contexts as well as by restricted, repetitive patterns of behaviour, interests, or activities. In the Diagnostic and Statistical Manual of Psychiatric Disorders (DSM 5), the criteria for ASD talk about specific patterns of behaviour including at least two of the following (APA, 2013).

• 1.

  Stereotypical or repetitive motor movements, use of objects, or speech.

• 2.

  Inflexible adherence to routines, insistence on sameness, and excessive resistance to changes.

• 3.

  Highly restricted, fixated interests that are abnormal in intensity or focus.

• 4.

  Hyper-reactivity or hyporeactivity to sensory aspects of the environment.

DSM 5 (APA, 2013) has adopted the umbrella term ‘autism spectrum disorder’ (ASD), which encompasses a set of heterogeneous neurodevelopmental conditions. The symptoms vary significantly across the spectrum; there is variation, for example, from severe intellectual disability to high intelligence. It is estimated that about 45% of individuals with autism have intellectual disability (Lai et al., 2014). DSM 5 does not talk about subtypes of autism, as opposed to DSM-IV (APA, 1994). There remains, though, in everyday language, the distinction between high-functioning autism and low-functioning autism. High-functioning autism has been frequently used interchangeably with the term ‘Asperger syndrome’, though it has been argued that these two are not synonymous due to differences in language command (Mukaddes et al., 2010). ‘High-functioning’ is generally used to refer to individuals in the spectrum who have normal or higher intelligence and who can use language in a superficially normal way (Tebartz val Elst et al., 2013).

In general, persons with autism have high rates of mental health difficulties in childhood, adolescence, and adulthood (Lai et al., 2020). They are thought to be at larger risk, as compared to the general population, of developing mental health comorbidities (Lai & Baron-Cohen, 2015; Hollocks et al., 2019). Anxiety and depression appear to be the most prominent ones (Lai et al., 2014). Van Steensel and Heeman (2017) meta-analytically examined 83 studies to investigate whether anxiety levels in children and adolescents with autism were elevated in comparison with typically developing (TD) youth. They noted that children and adolescents with ASD had higher anxiety levels, and this difference increased with IQ. A previous meta-analysis by van Steensel et al. (2011) on the prevalence rates of anxiety in children and adolescents with autism, found that 39.6% of them had at least one anxiety disorder. Hollocks et al. (2019) conducted a meta-analysis of 30 studies measuring anxiety in adults with autism; the pooled estimation of current and lifetime prevalence were 27% and 42% respectively for any anxiety disorder.

The above meta-analyses note variations in the levels of anxiety among different studies. Inconsistencies in the measurement of anxiety (and other psychiatric disorders) reflect differences in sampling as well as in diagnostic procedures and measures (Magiati & Howlin, 2019). Generally, studies on evaluating anxiety in individuals with autism have used instruments that have been validated with the general population. A problem is that these instruments do not address autism-specific triggers of anxiety (e.g., sensory hyper-sensitivities), while they may not differentiate between autistic and anxiety symptoms, which sometimes overshadow or overlap with each other. For example, social avoidance/withdrawal may express anxiety, but it may also relate to the social communication deficits of autism (Rodgers & Ofield, 2018; Uljarevic et al., 2016). It is only for children with ASD that an autism-specific measure been constructed, i.e., the Anxiety Scale for Children – ASD (ASC-ASD) (Rodgers et al., 2016).