Girls less likely to be diagnosed with autism than boys

6 Dec

A recent study out in the Disability and Health Journal shows that girls are more likely than boys to remain undiagnosed. The study, by David Mandell‘s group at the University of Pennsylvania, evaluated data from the Autism and Developmental Monitoring Network (ADDM). This is the same group that collects and analyzes data for the CDC’s autism prevalence studies.

Each ADDM study concentrates on children from a specific birth year. In this case, children born in 1994. They review records (medical, educational or both as available) to determine which children meet the criteria for autism. Some children already have a diagnosis of autism in their records. Other children are determined to be autistic via the ADDM review.

Prof. Mandell’s group found that for those with existing diagnoses at the time of review, girls and boys were similar in terms of average age of diagnosis and first age of evaluation. However girls were more likely to be undiagnosed (medical or educational) at the time of the ADDM review.

Here is the abstract.

Sex differences in the evaluation and diagnosis of autism spectrum disorders among children.

Giarelli E, Wiggins LD, Rice CE, Levy SE, Kirby RS, Pinto-Martin J, Mandell D.

Division of Biobehavioral Health Systems, University of Pennsylvania School of Nursing, Philadelphia, PA 19104, USA.
Abstract

BACKGROUND: One of the most consistent features of the autism spectrum disorders (ASDs) is the predominance among males, with approximately four males to every female. We sought to examine sex differences among children who met case definition for ASD in a large, population-based cohort with respect to age at first developmental evaluation, age of diagnosis, influence of cognitive impairment on these outcomes, and sex-specific behavioral characteristics.

METHODS: We conducted a secondary analysis of data collected for a population-based study of the prevalence of ASD. The sample comprised 2,568 children born in 1994 who met the case definition of ASD as established by the Autism and Developmental Disabilities Monitoring (ADDM) Network for ASD surveillance. Children who had a history of developmental disability and behavioral features consistent with the DSM-IV-TR criteria for autistic disorder, Asperger’s disorder, and Pervasive Developmental Disorder-Not Otherwise Specified in existing evaluation records were classified as ASD cases via two paths: streamlined and nonstreamlined. Streamlined reviews were conducted if there was an ASD diagnosis documented in the records. Data were collected in 13 sites across the United States through the ADDM Network, funded by the Centers for Disease Control and Prevention.

RESULTS: Males constituted 81% of the sample. There were no differences by sex in average age at first evaluation or average age of diagnosis among those with an existing documented chart diagnosis of an ASD. Girls were less likely than boys to have a documented diagnosis (odds ratio [OR] = 0.76, p = .004). This analysis was adjusted for cognitive impairment status. In the logistic model, with the interaction term for sex and cognitive impairment, girls with IQ of 70 or less were less likely than boys with IQ of 70 or less to have a documented diagnosis (OR = 0.70, 95% confidence interval [CI] = 0.50-0.97, p = .035). Boys with IQ greater than 70 were less likely than boys with IQ of 70 or less to have a documented diagnosis (OR = 0.60, 95% CI = 0.49-0.74, p < .001). This finding (less likely to have a documented diagnosis) was also true for girls with IQ greater than 70 (OR = 0.45, 95% CI = 0.32-0.66, p < .001). Girls were more likely to have notations of seizure-like behavior (p < .001). Boys were more likely to have notations of hyperactivity or a short attention span and aggressive behavior (p < .01).

CONCLUSIONS: Girls, especially those without cognitive impairment, may be formally identified at a later age than boys. This may delay referral for early intervention. Community education efforts should alert clinicians and parents to the potential of ASDs in boys and girls.

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6 Responses to “Girls less likely to be diagnosed with autism than boys”

  1. Esteleth December 6, 2010 at 20:44 #

    When I was in 3rd grade (i.e. 8 or 9 years old) I was evaluated for autism because I was showing all sorts of signs.
    The shrink told my parents, “Well, she fits a lot of the symptoms. But, she gets good grades (?!) and besides, she’s a girl.”
    No joke.
    I was not diagnosed until I was TWENTY years old, when I FINALLY began to get the support that I need to, you know, function in society.
    I want those twelve years of my life back. :/

  2. Prometheus December 7, 2010 at 01:43 #

    I’ve wondered for some time how much of the male bias in autism was an artifact of the commonly held belief that males were more likely to have autism that females. Given the “soft” diagnostic criteria – even in the medical diagnosis of autism – it seemed likely that at least some of the difference was due to fewer girls being evaluated for autism. And now we have some data saying just that.

    I am looking forward to more research in this area, since another commonly held belief about autism is that while girls are more rarely affected, they are also more severely affected. As this paper suggests, girls with milder forms of autism may be misdiagnosed (or not diagnosed at all) because of this commonly held belief (and others like it).

    Prometheus

  3. Theo December 7, 2010 at 18:48 #

    I still believe that there are FAR more girls with spectrum disorders than we know about. Girls are taught at an very early age to be social. THose who can not on thier own adapt in some fashion, usually by mimicking the actions of the girls around them.

    By doing this, and usually getting the good grades and not causing any trouble (I would hide my meltdowns by going into the bathroom when I felt them coming on) we are not going to be as noticeable as boys on the spectrum tend to be.

    Instead we are just considered eccentric, and it is considered a bit strange (at least in my case) that some girls feel more comfortable associating with males and with people who are older than them than with thier female, age peers.

    Some of us are even misdiagnosed. I was misdiagnosed with ADD and was treated with ritalin which nearly destroyed my stomach. I was not correctly diagnosed with AS (this time by a nuerolgist who specializes in diagnosing those on the spectrum) until I was 18 years old and in high school.

  4. Barbara December 9, 2010 at 19:56 #

    The absence of girls with a diagnosis is a major issue, and I believe can be tracked back to Asperger’s belief about ‘the extreme male brain’. Asperger was a teacher (please note, a GP, not psychologist or psychiatrist, but the Head of a hospital school). His cases were referred to him because these boys were acting out in school and disrupting. Anecdotally, all the spectrum kids I’ve seen in multiplex families have a mother, not necessarily but sometimes also a father, undiagnosed on the spectrum, and Asperger even noted that, too.

    Women with AS/autism are very seriously under-diagnosed, yet they are in the majority of autism bloggers. sbc’s testosterone theory needs some serious revision. My belief is that the sex difference is completely accounted for by diagnostic bias, as boys tend to act out more than girls – by about the ratio of 5:1. Girls fly under the radar at school.

    I believe that even if we take away the Rett’s complication, autism in males and females is 1:1. It’s the diagnosis that’s the problem. It isn’t a testosterone issue. It’s a diagnostic issue. And if research protocols demand a prior diagnosis of ASCs, then all research is screwed.

    Hmmm.

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