A Girl's-Eye View: Detecting and Understanding Autism Spectrum Disorders in Females
Recent research has estimated that the prevalence of autism spectrum disorder (ASD) is between 1 in 91 and 1 in 150 births. 1 2 Many more individuals are being diagnosed with ASD today than ever before, and investigators are working hard to better understand what is contributing to this increase in prevalence. What is less understood, however, is the difference in prevalence between boys and girls. The most reported statistic in the literature is that ASDs are 4 times more common in boys. Yet parents and professionals who work with girls with ASD have begun to wonder whether this statistic is indeed accurate. Are other factors playing a role such as differences in symptoms between males and females, the ability of assessment tools to detect ASD in girls, and research studies including more males than females in their sample? It is also very likely that male/female prevalence ratios vary according to the severity of the disorder. For individuals with a more "classic" presentation, including significant cognitive and language impairments, the 4 to 1 ratio may indeed be accurate, yet among clinic-based samples where individuals with mild difficulties are seen, it has been suggested that the ratio is closer to 10 to 1. 3 An important question is whether this is because females who do have an ASD are more likely to be affected to a great degree, or because females with milder presentations are not being detected in the same way as their male peers. Are we missing higher functioning girls with ASD?
How Can We Better Understand Females with ASD?
During a recent increase in media attention directed towards the experience of females with ASDs, Ami Klin, director of Yale University's autism program, described females with autism as "research orphans" in an article in The New York Times 4 entitled "What Autistic Girls Are Made Of." Klin suggested that because research studies primarily include samples of males with ASDs, their findings may not be applicable to females. As a result, what we learn from such research may do little to shed light on the biology, development, experience, assessment, and treatment of girls and women on the autism spectrum.
Though limited in number, research studies are emerging that are asking questions about differences between males and females with ASDs, and what these differences may mean for issues related to assessment and treatment. Studies have begun to examine differences in symptom presentation, developmental trajectories, prevalence rates, assessment, and diagnosis. 5 6 7 8 9 10 11 12 13 We have much to learn from this small but growing body of literature addressing sex differences in ASDs, and also from another area of research that has received even less attention but is equally, if not more important: understanding how girls with ASD differ from neurotypical girls, or girls with other neurodevelopmental conditions such as attention deficit hyperactivity disorder (ADHD).
Summary of Research Findings of Differences between Boys and Girls with ASDs
What follows is a general summary of the above-referenced research. Specific findings may vary depending on the age of the research participants, level of intellectual ability, the type of sample studied (clinic or laboratory), and how skills and behaviors were measured (observed or parent report).
- As a group, males with ASD score higher than girls with ASD on intellectual assessments. (This might actually support the notion that higher functioning girls are not being diagnosed and included in these calculations.)
- The play of boys with ASD has been found to be more repetitive and restricted in range.
- As assessed on diagnostic instruments for autism, the communicative abilities of girls with ASD have been observed to be stronger (e.g., pointing, gaze following).
- Boys and girls with ASD may experience different developmental trajectories related to social difficulties with boys demonstrating more difficulties earlier in life, and girls expressing greater impairment in early adolescence.
- Boys with ASD may tend to engage in disruptive behavior to gain objects, while girls with ASD may tend to engage in disruptive behavior to get attention.
- Girls with ASD may be more able to focus and may be less distractible than boys with ASD.
- Young girls with ASD have been found to appear more anxious and depressed than boys with ASD.
- Parents may overestimate the social difficulties or impairments of their daughters because they have (and society has) greater expectations for how girls should behave in the social and communicative domains.
Detecting ASDs in Females
So...are girls with ASDs being missed or overlooked during an evaluation because they have different characteristics than boys? 9 14 15 Kopp and colleagues 9 recently published a study in which they examined clinical characteristics of 100 girls, ages 3 to 18 years, with average intellectual abilities who were referred to a child neuropsychiatric clinic for problems with social interactions, attentional or academic difficulties, or tics. Though only 12 of the girls had been diagnosed previously with ASD, ADHD, or a tic disorder, 46 girls met criteria for an ASD based on the findings of the investigators' comprehensive assessment. Co-occurring ADHD was observed in 95% of the school age girls with ASD, but with fewer symptoms than those of girls who received a primary ADHD diagnosis. Compared to an age-matched community sample of neurotypical females (minimum full scale IQ score of 80), girls with ASD and ADHD experienced more psychiatric symptoms related to the disorder such as anxiety and sleep difficulties, had lower full scale IQ scores, and experienced greater global functioning impairments. Kopp and colleagues' study is the first to evaluate girls with ASD, ADHD and neurotypical controls. Their findings strongly suggest that when girls with social and attentional difficulties present at a clinic for a diagnostic evaluation, it is essential to carefully evaluate for ASD and ADHD diagnoses, and that much more research is needed to better understand the expression of these disorders in females.
- Referral for further evaluation if scores are close to, but do not meet cut-off, on an autism screening measure
- Comparison of a girl's social and communicative abilities to what is considered normative for females of her age and cognitive ability
- Careful examination of social and communicative difficulties in the absence of significant disruptive behavior
- Avoiding comparison of a girl's set of symptoms to the prototypical male presentation of ASD
- Consideration of how a girl may perform in a simple social setting where she only has to interact with one other person versus how she may perform in an unstructured, real-world environment with peers
- Understanding a girl's social network and taking into account whether she has a "mother hen" friend who has supported her in the social world (which may have masked her social deficits)
- Consideration that deficits in girls may become more apparent over time, particularly in early adolescence
Over the last 15 years, and throughout the writing of our book Girls Growing Up on the Autism Spectrum: What Parents and Professionals Should Know About the Pre-Teen and Teenage Years, 14 I have worked and communicated with hundreds of families of girls and women with ASDs. Pursuit of a diagnosis for many of these families has been difficult and fraught with numerous roadblocks including incorrect diagnoses along the way and frustrating experiences with the professional community. People who work with individuals on the spectrum need to develop a much better understanding of girls with ASDs, including how to support their families. However, I am encouraged that researchers and care providers are moving in the right direction towards learning how best to detect ASDs in girls and women and towards asking meaningful sex-related research questions.
More About the Author
Shana Nichols, Ph.D., is a licensed clinical psychologist and researcher who has worked in the field of ASDs and child development for more than 12 years. She received her Ph.D. in clinical psychology from Dalhousie University, Halifax, Canada, and did her internship and post-doctoral training at JFK Partners Center for Autism in Denver, Colorado. She currently specializes in adolescence and growing up, dual diagnosis and mental health issues, and the experiences of girls with ASDs. Originally from Ontario, Canada, she now lives on Long Island, New York, and is clinical director of the Fay J. Lindner Center for Autism and Developmental Disabilities. Her book, entitled Girls Growing Up on the Autism Spectrum: What Parents and Professionals Should Know About the Pre-Teen and Teenage Years, was published by Jessica Kingsley Publishers in December 2008. She was a recipient of the Canadian Psychological Association Certificate of Academic Excellence in 2005 Award for her Ph.D. thesis work, and she has received grant support for her work in sexuality, puberty, and ASDs from the Organization for Autism Research, the Society for the Scientific Study of Sexuality and Autism Coalition/Autism Speaks.
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