Asperger syndrome (AS) is an Autism Spectrum Disorder (ASD) characterized by significant impairments in social interaction, and rigid, stereotypical, or repetitive behaviours that exist alongside normal language and cognitive skills (Fitzgerald & Corvin, 2001). Researchers often use the terms Asperger syndrome and high-functioning autism interchangeably (Attwood, 2006), and so for the purposes of this paper, Asperger syndrome will encompass both diagnoses, and assume an IQ in the normal range, i.e., > 70. The ratio of males to females with AS is currently about 10:1, and on average, boys are referred ten times more often for diagnostic assessment (Wagner, 2006). Overall, the lack of knowledge about girls and women with AS is mirrored by a relatively small amount of empirical research dedicated to this population (Thompson, Caruso, & Ellerbeck, 2003). Much of the available literature includes clinical observations, case studies, and anecdotal evidence.
Some feel that the uneven gender ratio is a natural reflection of biological sex differences. Jones, Skinner, Friez, Schwartz, and Stevenson (2008) propose a sex-linked genetic cause, and argue that the single X chromosome in males is inherently vulnerable, creating a lower threshold of susceptibility to AS. Alternatively, Baron-Cohen and Wheelwright (2004) hypothesize that gender differences in brain specialization may explain the male-dominated ratio, and contend that while females are naturally better at empathizing, males tend to think in a systemizing way. They conceptualize Asperger syndrome as an extreme systemizing form of the normal male brain that may develop due to high levels of testosterone exposure in utero. The question arises, however, as to what extent sex differences are biological, or influenced by sociocultural factors.
In contrast to the researchers that find support for the current gender ratio, many believe it is inaccurate (e.g., Attwood, 2006; Rastam, 2008). Thompson et al. (2003) claim that a long-standing sex bias in AS research has resulted in diagnostic criteria too dependent on a male prototype, and point out that 80% of all ASD study samples have been male, on average. They suggest further that our present knowledge about ASD is actually knowledge about males with ASD. Nyden, Hjelmquist, and Gillberg (2000) highlight comparable issues in the diagnostic criteria for Attention Deficit Hyperactivity Disorder (ADHD), while Rastam (2008) parallels the development of criteria for clinical eating disorders, based largely on the signs and symptoms prevalent in females. Hully and Lamar (2006) suggest that overdependence on a male prototype means that traits in females must appear exaggerated for diagnosis. Ironically, researchers are finding it difficult to obtain samples on females that are large enough to allow for comparison by sex (Hartley & Sikora, 2009). This paper will explore how psychiatric disorders may mask AS in females, gender differences in phenotypic expression that can cause diagnostic confusion, and the attitudes and behaviour of others toward females with AS that can contribute to a missed diagnosis.
Several disorders have the potential to overshadow Asperger syndrome in females including depression, ADHD and Anorexia Nervosa (AN) (Hartley & Sikora, 2009; Rastam, 2008; Ryden & Bejolet, 2008). Researchers feel that the risk of misinterpreting signs and symptoms is strong, and could lead to misdiagnosis, or failure to recognize AS as the primary disorder (Cooper & Hanstock, 2009; Ryden & Bejolet, 2008). Hully and Lamar (2006) observed that as girls grow older, the presenting problem is less often associated with a developmental disorder, and stress that clinicians must take a detailed patient history to rule out AS in females. Accordingly, Ryden and Bejolet (2008) found that adult women with AS comprised a large portion of the psychiatric outpatients that they studied (39 females and 44 males), and speculate that many females do not receive an accurate diagnosis until they seek treatment for a comorbid disorder.
Although the gender ratio for childhood depression is 1:1 in the general population, by adolescence, females are three times more likely to receive a diagnosis of depression (Cooper & Hanstock, 2009). In fact, Ryden and Bejolet (2008) found a history of depression most often in patients that had not received a diagnosis of AS until adulthood. This could underscore a lack of awareness of how Asperger syndrome looks at different ages, and in females. Symptoms that often cause diagnostic confusion include a flat affect, minimal facial expressions, flat intonation in speech, irritability, and social isolation (Cooper & Hanstock, 2009). Hartley and Sikora (2009) found that girls with ASD, as young as 1.5 years of age, displayed an anxious or depressed affect more often, which lends support to this idea. In addition, Cooper and Hanstock (2009) discovered that Jane, initially referred for confirmation of a mood disorder, had a stable baseline mood over a long period. They concluded that failure to recognize significant social impairments, along with a flat affect and monotone voice, a number of school changes, and normal IQ and language skills, resulted in a misdiagnosis of depression.
Holtmann et al. (2007) found that females, across the entire sample that they studied, had significantly more attention difficulties than males, and similarly, Nyden et al. (2000) established that girls, aged 8 to 12 years, had greater impairment on the Freedom from Distractibility subscale than boys in the same age range. Greater attention difficulties in girls and women suggest that a misdiagnosis of ADHD may occur more often in this population. In accordance with this, Ryden and Bejolet (2008) assert that the lack of common sense and social disinhibition inherent in AS could be mistaken for impulsiveness, further increasing the likelihood of an incorrect ADHD diagnosis.
Ryden and Bejolet (2008) also discovered that adult female patients with Asperger syndrome scored higher on scales measuring borderline and passive aggressive traits, and mood instability, despite presenting with the same core AS features as males. Holtmann et al. (2007) uncovered a similar trend in their analysis of a matched subgroup of males and females.
Although core impairments were also equal in both genders, girls scored higher on scales measuring peer relationship impairments, social immaturity and dependency, as well as compulsive and bizarre behaviour, with older females scoring the highest. Similarly, Cooper and Hanstock (2009) found that Jane’s social impairments and deviance from her peers were more obvious as she grew older.
These findings suggest that if a clinician fails to notice a girl’s severe social difficulties in childhood, the result could be an incorrect diagnosis of BPD later on. Likewise, Ryden and Bejolet (2008) state that undetected AS might exist in a subgroup of older females diagnosed with BPD, which further emphasizes the importance of taking a detailed patient history when considering diagnosis. In addition, they stress that concepts of personality disorder and abnormal personality traits are difficult to separate in Asperger syndrome, and propose that a different model is needed to explain “odd personality” in this population.
Written by A. MacMillan