Girls with autism receive a diagnosis, on average, nearly 1.5 years later than boys


A new study analyzing the first 1,000 participants in the Rhode Island Consortium for Autism Research and Treatment (RI-CART) identifies key trends in the presentation and diagnosis of autism spectrum disorder. The study was published in Autism Research on Monday, Jan. 20.

The first finding was that girls with autism receive a diagnosis, on average, nearly 1.5 years later than boys.

This is likely because parents and clinicians tend to notice language delays as the first sign of autism, and girls in the study exhibited more advanced language abilities compared to boys, said study authors Stephen Sheinkopf and Dr. Eric Morrow.

Autism is far more common in boys. The RI-CART study found more than four times as many boys as girls with autism; however, given the large size of the sample, the study was well-powered to evaluate girls with autism.

The finding that girls with autism are diagnosed later is clinically important, said Morrow, an associate professor of molecular biology, neuroscience and psychiatry at Brown University.

“The major treatment that has some efficacy in autism is early diagnosis and getting the children into intensive services, including behavioral therapy,” Morrow said. “So if we’re identifying girls later, that may delay their treatments.”

Sheinkopf, an associate professor of psychiatry and pediatrics at Brown, emphasized the importance of early recognition.

“We need to think about how we can improve recognition of autism in individuals — including many of these girls — who don’t have the same level of primary language delay but may have other difficulties in social communication, social play and adapting to the social world,” he said.

“And as we improve diagnosis for the full range of individuals in the early years, we must also rethink early interventions to make sure they’re designed appropriately for children who might need assistance on more nuanced elements of social adaptation. We need to refine treatments so they cater to individual needs.”

Based at Bradley Hospital in East Providence, the team behind RI-CART represents a public-private-academic collaborative — a partnership between researchers at Brown, Bradley Hospital and Women and Infants — that also involves nearly every site of service for families affected by autism in Rhode Island.

The study team also integrated members of the autism community, family members and particularly the Autism Project, a family support service for autism in the state.

By engaging both the community and treatment providers, the study enrolled more than 20 percent of pediatric-age individuals with autism in Rhode Island. Participants were recruited from all geographic regions of the state, and as part of the study, they were given rigorous in-person assessments.

Most participants had received an autism diagnosis prior to entering the study (a community diagnosis), and their diagnosis was subsequently confirmed by an in-person assessor, meaning that they also received a research diagnosis.

The study also included individuals whose diagnoses were less clear cut. For example, some individuals received either a community diagnosis or a research diagnosis, but not both. Other individuals were referred to the study but did not have evidence of autism from either a community evaluation or the research assessment.

“The group that was diagnostically less clear-cut represents the complexity that clinicians encounter on a daily basis, so it’s a realistic sample in that sense,” Sheinkopf said. “This full range of heterogeneous autism presentation is rather unique to our study.”

The other major finding of the study was that people with autism frequently exhibit co-occurring psychiatric and medical conditions.

Nearly half of the participants reported another neurodevelopmental disorder (i.e., attention-deficit/hyperactivity disorder (ADHD) or intellectual disability), while 44.1 percent reported a psychiatric disorder, 42.7 percent reported a neurological condition (i.e., seizures/epilepsy, migraines, tics), 92.5 percent reported at least one general medical condition and nearly a third reported other behavioral problems.

“These co-occurring conditions need also to be a focus of treatment for patients,” Morrow said.

“Many people with autism need support for the psychiatric and emotional challenges that are prevalent in people who share this one diagnosis,” Sheinkopf added. “These are clinically complicated individuals who deserve strong, sophisticated, multidimensional, multidisciplinary care.”

Sheinkopf and Morrow say they’re encouraged by the support and collaboration of a variety of health care providers, community members and particularly, by the level of commitment shown by the families who participated in the study.

Going forward, they’re hopeful that the RI-CART registry will lead to more studies that will improve the lives of people with autism and their families, particularly because the cohort currently involves such a wide age range of participants, including individuals with autism ages 2 to nearly 64.

The other major finding of the study was that people with autism frequently exhibit co-occurring psychiatric and medical conditions. Image is in the public domain.

“Given that autism is a developmental disorder, the field really needs to focus on longitudinal studies: following people’s development and transitions,” Morrow said. “I think we’re going to learn even more when we follow children from a very young age as they develop, including into adulthood.”

In addition to Sheinkopf and Morrow, other Brown University authors on the study were Carolyn McCormick, Brian Kavanaugh, Danielle Sipsock, Giulia Righi, Lindsay Oberman, Daniel Moreno-De Luca, Ece Gamsiz Uzun, Carrie Best, Beth Jerskey, Pei-Chi Wu, Rebecca McLean, Todd Levine, Hasmik Tokadjian, Kayla Perkins, Elaine Clark, Brittany Dunn, Alan Gerber, Elena Tenenbaum and Thomas Anders. Additional contributors include Joanne Quinn and Susan Jewel from the Autism Project.

Funding: The study was funded by the Simons Foundation Autism Research Initiative (286756), the Hassenfeld Child Health Innovation Institute at Brown University, the National Institutes of Health (though the National Center for Advancing Translational Sciences), the Clinical and Translational Sciences Award (KL2 TR002530 and ULI TR002529) and the National Institute of Mental Health (R25 MH101076 and T32 MH019927).

RI-CART received pilot support from the Carney Institute for Brain Science at Brown, the Norman Prince Neuroscience Institute and the Department of Psychiatry and Human Behavior.A

Reports on the prevalence of autism inevitably depend on the criteria used. The concept of autism spectrum disorders has now broadened considerably beyond original descriptions,1 2 and clinicians also now base their diagnosis on fewer symptoms than a decade ago.3 Additionally, there is now increased awareness about autism; hence the reported prevalence of autism has increased. Several systematic reviews have attempted to synthesise research studies on prevalence, with overall prevalence varying, dependent on the studies included, for example, their age-ranges, years the studies were conducted in (and hence criteria), data-collection methods, size and representativeness of included studies. Even when restricted to studies published since 2000, studies selected for inclusion in the reviews have shown wide ranges in reported prevalence.4–7 Recent reviews are summarised in table 1.

Table 1

Examples of findings from systematic reviews of recent studies on childhood/youth prevalence of autism

ReviewNo. of studiesPublication dates of studiesMedian prevalence/1000Range/1000
Autistic disorder
French et al., 20134Autistic disorder262000–20112.20.8–9.4
Asperger syndrome*131998–20112.10.5–2.8
Elsabbagh et al., 20125Northern European162000–20081.90.7–3.9
Western Pacific122000–20111.20.3–9.4
South East Asia/East Mediterranean1
Tsai, 20146432001–20132.80.3–19.0
Pervasive developmental disorder
French et al., 20134342000–20116.20.6–26.4
Elsabbagh et al., 20125Northern Europe142000–20116.23.0–11.6
Western Pacific42004–20111.6–19.0
South East Asia/East Mediterranean42007–20120.1–10.7
Tsai, 20146612000–20147.00.2–26.4
Adak and Halder, 20177252005–20159.20.7–26.4

*The authors comment on dubious quality of results.

The included age range in studies is likely to be critical in these reported rates, related to the age at which children are diagnosed. This, however, seems to be little investigated. A California, USA, study demonstrated that as well as rates of diagnosis of autism increasing, this was particularly so among preschool children,8 while a large Swedish study found that the number of autism symptoms in children diagnosed with autism had fallen in children diagnosed at age 7–12 years, but not at age 1–6 years.3 

In the National Survey of Children’s Health, USA, 259 (24.6%) of children with autism were diagnosed at <3 years of age, 479 (44.5%) at 3–5 years and 383 (30.9%) at >5 years of age.9 A review has suggested there remains considerable variation in age at diagnosis.10 Further current data are clearly needed.

One reason why it is important to understand prevalence of autism is that the health profile of children and young people with autism is thought to differ from that of typically developing children and requires interventions and supports.11–13 Therefore, these combined factors, that is, knowledge of prevalence and health profile of autistic children, are essential for planning and delivery of services.

Subjective general health status is commonly measured in general population studies, and has been demonstrated to be extremely valid, with a strongly predictive linear gradient across health status (from best to poorest) being associated with subsequent number of medical appointments, hospital admissions and mortality.14–17 It is, therefore, important to measure if there are general health status differences in children and young people with autism compared with other children. However, in terms of general health status of children and young people with autism, there has been very little research.

A study in USA reported parent-rated general health for 895 young people with autism aged 13–25 years at baseline, at five time points across 2001–2009, but did not include a general population comparison group.18 General health was rated as excellent, very good, good or fair/poor. Fair/poor ratings were reported for 6.6% in 2001, 6.4% in 2003, 7.6% in 2005, 6.1% in 2007 and 6.6% in 2009.18 A large study presenting data from the 2011–2012 National Survey of Children’s Health identified 1188/56 746 children with autism under the age of 18, who were found to have significantly lower log odds of health (−1.30, p<0.001) compared with all other children.19

To our knowledge, no other studies have investigated reported general health status of children and young people with autism, nor drawn direct comparisons with the general population. This appears to be a major gap in our knowledge.

This study aimed to investigate, on a large scale (the entire population of a country—Scotland) (1) the prevalence of autism, and age of reporting/identifying autism in childhood and (2) the general health status of children and young people with autism compared with those without autism.

Brown University


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