By Dr Michelle Garnett and Prof Tony Attwood
Both autism and ADHD are characterised by difficulties with executive function, and they tend to co- occur. Research has shown over several decades now that being autistic and having ADHD is very common and occurs in the majority (60%) of autistic children and adolescents (Stevens, Peng & Barnard-Brak, 2016). A more recent meta-analysis showed the range across 63 studies to be between 40 and 70% (Rong et al, 2021). There is evidence from both family and twin studies that autism and ADHD share a common genetic base where approximately 50 to 72% of the contributing genetic factors in both conditions show overlap (Leitner, 2014). A recent review of 26 studies examined executive functioning in autistic children who had ADHD and concluded that there was a neurocognitive endophenotype where autism and ADHD share more common features than they do differences (Craig et al, 2016).
*NB: Wherever the female gender is referred to in this article we are referring to the gender assigned at birth, rather than the gender identified with which may be different.
An increase in the prevalence of ADHD and Autism but missing the girls
ADHD is the most common neurodevelopmental disorder, and its prevalence has increased during the years from 1997 to 2016 from 6.1% to 10.2% respectively (Danielson et al 2018, Xu et al, 2018). The prevalence of ADHD in boys is up to 9 times higher than in girls in clinical samples (Nussbaum, 2016). However, in adulthood, the estimated prevalence of adult ADHD is less than two times higher in men than women (Kessler et al, 2006). Since for ADHD to be diagnosed the person must show symptoms in childhood, clearly many females with ADHD are being missed.
The prevalence of autism has also increased in the same period, from 0.4% in 1996 to 2.7% amongst children aged 8 years in the United States, according to reports from the Centre for Disease Control (Maenner et al, 2023). Similarly, autism has been missed in girls and women. Posserud and colleagues (2021) in a large population study in Norway found the male to female ratio for autistic children aged 4 to 10 years old was 4.46:1 but increased to 2.57:1 in autistic adults. Interestingly, the authors found that comorbid ADHD significantly increased the male percentage ratio in autistic children.
A recent study found that 1.2% of US children have co-occurring autism and ADHD (Casseus, 2022) and found that those diagnosed with both conditions were more likely to be male than female.
Reasons for missing ADHD in females
Just as autism presents differently in females, so does ADHD. Several characteristics of the presentation of ADHD in women and girls have been described by Quinn and Madhoo (2014) based on their overview of 41 articles. Specifically, these include:
- greater incidence of low self-esteem,
- more difficulty with peer relationships,
- coexisting anxiety and affective disorders,
- the development of coping strategies, such as masking.
There are also several studies now that show that inattentiveness is generally more common than hyperactivity and impulsivity in girls with ADHD (Biederman, 1999; Novik et al, 2006; Gershon, 2002). Generally, females have fewer symptoms as measured by the DSM-5- TR (APA, 2022) criteria, but are just as impaired as males by the symptoms (Quinn & Madhoo, 2014).
A young person with the inattentive profile of ADHD is generally quieter and less disruptive than a young person with the hyperactive/impulsive profile in the classroom, therefore girls are less likely to be picked up by teachers. Ohan and colleagues (2005) found that mothers generally felt that the DSM-5 criteria for ADHD more accurately described boys than girls. These findings mean that girls are less likely to be referred for a diagnostic assessment for ADHD than boys.
Clinically, we have also found that “diagnostic overshadowing” can occur both ways, that is once a diagnosis of autism is made, ADHD may be missed, and vice versa. Research shows that autistic females use camouflaging and masking more often than their male counterparts (Cooke et al, 2021), and we have found that the girls and women are masking, not only their autistic features, but also their ADHD, anxiety, and depression.
The importance of recognising autism and ADHD for females
One of the clear problems of missing the diagnosis of ADHD is that the individual will not be understood from an ADHD perspective and so misses the opportunity of accurate self-understanding and appropriate supports, including medication if she chooses. Without understanding that a different neurology is at the root of the problem expectations from others and herself will be unrealistic in terms of her capacity for attention, self-regulation, and disinhibition of responses, leading to the development of secondary conditions, including behavioural disorders, anxiety, and depression.
Current best practice guidelines recommend assessing for both autism and ADHD, and providing therapy and support for both when both are diagnosed. Misdiagnosis can lead to not only missing out on appropriate support and treatments but also receiving inaccurate explanations for the difficulties, lack of reasonable adjustments for neurological differences and inappropriate treatment, including inappropriate medication.
Although not uniformly, medication is seen as being a first line treatment for ADHD, due to the positive results for most participants (e.g. Pearson et al 2020). However, research shows that medication is considered as a treatment strategy for girls with ADHD less often than it is for boys with ADHD (Coles et al, 2012). A large study from Sweden (Johanssen et al, 2020) found that autistic individuals with ADHD were less likely to start medication due to clinicians missing ADHD once autism had been discovered.
Anxiety and affective disorders that commonly appear for girls with ADHD tend to persist into adulthood (Biedermeier et al, 2012, Willems et al, 2009). Studies have indicated that girls with inattentive type ADHD tend to report lower levels of arousal, and thus may be misdiagnosed with dysphoria rather than ADHD (Quinn, 2005). Also, ADHD women with ADHD – combined type, including impulsivity and hyperactivity, can be misdiagnosed with bipolar disorder (Waite, 2007).
Women with ADHD entering the workforce can experience performance issues that affect their productivity and the quality of their work. Knowing that they had ADHD would allow both themselves and their employer to understand the accommodations and supports that would assist them to be able to work more productively. Without support, understanding and reasonable adjustments, autistic women with ADHD risk being placed on performance review, potentially losing their job, and suffering low self-esteem, possible mental health issues and financial hardship.
Where to from here?
Diagnosticians, therapists, and educational staff need to be aware of the high co-occurrence of ADHD in autistic individuals, and how to provide appropriate supports and therapy when a person is both autistic and has ADHD. Understanding the similarities and differences, how to recognise the inattentive ADHD subtype, and what to do will significantly impact the person in a positive way.
We raise awareness about the association between autism and ADHD in our online course:
References
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