Considering the Co-Occurrence of Autism and Attention Deficit/Hyperactivity Disorder

David Nicholas, PhD; Adam McCrimmon, PhD; Emma Climie, PhD; & Aisouda Savadlou
This literature review provides an overview of research on the co-occurrence of ASD and ADHD, and features quotes from a conversation with Dr. Adam McCrimmon, an autism expert and Associate Professor of Applied Child Psychology at the University of Calgary, and Dr. Emma Climie, an ADHD expert and Associate Professor of Applied Child Psychology also at the University of Calgary.



David Nicholas PhD (1), Adam McCrimmon, PhD (2), Emma Climie, PhD (2), & Aisouda Savadlou (1)
(1) Faculty of Social Work, University of Calgary
(2) Werklund School of Education, University of Calgary



Background about this toolkit:

Autism Spectrum Disorder (ASD, hereafter termed "autism") and Attention Deficit/Hyperactivity Disorder (ADHD) are neurodevelopmental conditions with diverse clinical presentations. The traits associated with each may display differently from one person to another (APA, 2022; Masi et al., 2017). In the past two decades, research has increasingly found that autism and ADHD can co-occur and that a sizeable proportion of individuals have the two neurodevelopmental conditions simultaneously.
This literature review provides an overview of research on the co-occurrence of autism and ADHD, and features quotes from a conversation with Dr. Adam McCrimmon, an autism expert and Associate Professor of Applied Child Psychology at the University of Calgary, and Dr. Emma Climie, an ADHD expert and Associate Professor of Applied Child Psychology also at the University of Calgary. This review features the following: an overview of i) autism, ii) ADHD, iii) co-occurring autism and ADHD, and iv) expert recommendations from Dr. McCrimmon and Dr. Climie.



i) Autism Spectrum Disorder

Autism is a neurodevelopmental condition with characteristics appearing early in development (American Psychiatric Association [APA], 2022). There are varying perspectives on autism and other developmental presentations, reflective of orientations such as the social model of disability, the neurodiversity perspective, and the traditional medical model. The social model of disability is concerned about social structures and barriers that exclude individuals from participating in society (Shakespeare, 2017). The neurodiversity perspective views individuals “through the lens of human diversity” as individuals with both strengths and challenges (Robertson et al., 2009). The three fundamental principles of neurodiversity are that 1) neurodiversity is valuable, and reflects the natural variation in humans, 2) the concept of a ‘normal’ or ‘healthy’ brain is a social construction, and 3) like other forms of human diversity, the acceptance of neurodiversity can be “a source of creative potential” (Walker, 2014). This perspective recognizes that “living in a society designed for non-autistic people contributes to, and exacerbates, many of the daily living challenges that [A]utistic people experience” (Robertson et al., 2009).

More traditionally, the Diagnostic and Statistical Manual of Mental Disorders (5th ed., DSM-5 text rev.; APA, 2022) reflects a more deficit-oriented approach to autism. The 2013 edition of the DSM-5 (APA, 2013) combined previously distinct conditions including autism (i.e., childhood autism, Kanner’s autism, etc.), Asperger’s disorder, childhood disintegrative disorder, and Pervasive Developmental Disorder-Not Otherwise Specified under the single diagnosis of autism. The term ‘spectrum’ or ‘constellation’ (Fletcher-Watson & Happé, 2019, pp. 39-41) are used since factors such as age, developmental stage, and autistic traits can impact how autism is presented in an individual (APA, 2022; Doernberg & Hollander, 2016).

According to a traditional DSM-5 conceptualization or diagnosis of autism, the two main features of autism are challenges in social communication and the presence of restricted and repetitive behaviours and interests (APA, 2022). Some examples of social and communication challenges in Autistic individuals include differences or challenges in reciprocal conversation; navigation of social interactions; understanding of facial expressions, emotions, or gestures; and interaction with peers. Restricted and repetitive behaviours can take the form of maintaining routine and sameness, sensory over- or under-stimulation, having passionate areas of interest, or engaging in repetitive movements or speech (APA, 2022).

Characteristics of autism can be identified as early as toddlerhood (12-24 months) based on delayed developmental milestones or loss of previously acquired skills; however, this timeline can reflect differences in developmental presentation (APA, 2022). Early features of autism include delayed language and challenges in social skills or social interactions, as well as communication and play patterns that are different from non-Autistic peers (APA, 2022). While it is more common to receive an autism diagnosis in childhood, some individuals may be diagnosed in adulthood. Individuals may seek a professional opinion following the diagnosis of their child or an immediate family member, or perhaps after substantial challenge in their home and work life (see Crane et al., 2018 and Pohl et al., 2020).

The transition to adulthood can bring challenges for Autistic individuals. When asked about autism across development, Dr. McCrimmon explained, “As [Autistic individuals enter] adulthood, you can certainly see difficulties in living independently, and some challenges with employment and education. So, autism does change with age, and how we recognize and support Autistic individuals certainly needs to change as well.” The 2012 Canadian Survey on Disability revealed that 78.5% of individuals with autism were not participating in the labour force and those who were employed had fewer hours of paid work per week in comparison to the average for individuals with developmental disabilities (Zwicker et al., 2017). It is recognized that further consideration of variation is needed, such as differences for adults with and without intellectual disability, but overall, improved supports and barrier reduction in employment are needed.

The global prevalence of autism in the child and adult population is estimated at around 1% (APA, 2022). The 2019 Canadian Health Survey on Children and Youth reported a 2% prevalence rate of autism in children between 1-17 years of age (Public Health Agency of Canada, 2022). In this sample, boys were four times more likely to be diagnosed with autism than girls (Public Health Agency of Canada, 2022). This 4:1 sex ratio has been consistently reported (APA, 2022; Yeargin-Allsopp et al., 2003); however, recent research suggests this ratio is inaccurate (Loomes et al., 2017). This disparity can be attributed to several factors including diagnostic bias towards male presentations of autism, and overlooking autistic traits in girls (Bargiela et al., 2016; Lai et al., 2015; Loomes et al., 2017). Regarding the role of sex and gender in autism, Dr. McCrimmon elaborated that, “There is currently an understanding that the classic description of autism seems to be more based around men than it does women, and what we typically think of as autism seems to be more obvious and apparent in men as opposed to women. We tend to see that women are more successful at hiding what might be their natural, more different social behavior, to try and appear more engaging or more interactive with others, whereas men can do that less frequently. Women may tend toward interests that are more socially acceptable. And so, it is up to the people recognizing and supporting them to know what kind of supports they might need.”

Autism Supports

Current services aim to decrease the impact of speech, learning, and movement challenges for Autistic individuals (Abraham et al., 2022; Ip et al., 2019). These services are often multi-disciplinary and provide psychosocial support through different means including educational programs for families and Autistic individuals (Abraham et al., 2022), behavioural therapies (Vismara & Rogers, 2010), and other forms of therapy for improving social interactions and speech production (e.g., Mayer-Benarous et al., 2021). No standard pharmacological approach is used in autism; however, medication may be prescribed to lessen the impact of co-occurring issues such as sleep interruption, inattention, and hyperactivity (Abraham et al., 2022; Howes et al., 2018; Ip et al., 2019).

Other Conditions or Issues

Nearly three out of four Autistic individuals present with other co-occurring conditions (Sharma et al., 2018), some of which include ADHD (Leitner, 2014), anxiety (Muris et al., 1998; Mayes et al., 2011; Simonoff et al., 2008), depression (Mayes et al., 2011), epilepsy (Besag, 2017), and inflammatory bowel disease (Lee et al., 2018). In Canada, the most common co-occurring condition among Autistic children and adolescents is ADHD (36.5%; Public Health Agency of Canada, 2022).

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ii) Attention Deficit/Hyperactivity Disorder

The DSM-5 describes ADHD as a neurodevelopmental disability with a strong heritable component, meaning that the chance of having ADHD is greater if an immediate family member has ADHD (APA, 2022). This conceptualization characterizes ADHD by two main features of inattention and hyperactivity-impulsivity (Abraham et al., 2022; APA, 2022). These features lead to three different presentations: 1) combined presentation (when there is both inattention and hyperactivity-impulsivity), 2) predominantly inattentive presentation, and 3) predominantly hyperactive/impulsive presentation (APA, 2022). It is important to note that there is a high degree of variability in ADHD presentations. Dr. Climie, an ADHD expert, emphasized this heterogeneity or diversity in presentation: “When we are thinking about common features of ADHD, we can certainly talk about the symptoms and the behaviour, but I think one important feature of ADHD is that there is no typical profile. If you have met one child with ADHD, you have met one child with ADHD because 100 different kids with ADHD will have 100 different symptom presentations. This is important to keep in mind, especially when you are considering intervention and supports. These are not going to be a ‘one size fits all’ type of approach.”

To receive a diagnosis of ADHD, the following criteria must be met: 1) six or more features of inattention and/or hyperactivity-impulsivity are present, 2) features of ADHD must be observed prior to age 12 years, 3) presenting features must persist for at least six months, and 4) ADHD traits must be observed in two or more settings such as work, school, or home (APA, 2022). The identification of ADHD traits is challenging in children younger than four years of age; however, upon school entry, the features of inattention and/or hyperactivity-impulsivity become more apparent (Abraham et al., 2022). As explained by Dr. Climie, “We often see more of the hyperactive behaviors in younger children. We see an inability to sit down; they may be always moving, are not able to focus, and may be up and down, and all over the place. It is when they get into school that the more inattentive behaviours tend to show themselves. So, while they may be able to sit in a chair, they are still not able to sit and focus on the work that they are doing.” A reviewer reflected and added, “But how would this change if the child was asked to spend all day outside helping their parent on their farm? Would the child still be unable to focus and learn? Probably not. So perhaps we need to emphasize that the environmental demands of the regular classroom are not particularly well-aligned to the needs of the child’s neurodivergent brain.”

An ADHD diagnosis criterion that was modified in the DSM-5 was changing the age of onset (i.e., when ADHD traits were first recognized) from seven to 12 years old (APA, 2013). This change was made following publications that revealed early- and late-age of onset individuals did not differ in terms of trait, trajectory, and outcomes (Chandra et al., 2016; Faraone et al., 2006; Rohde et al., 2000).

The features of ADHD, mainly hyperactivity-impulsivity, tend to decrease as individuals get older (Biederman et al., 2000; Döpfner et al., 2014); however, one does not outgrow ADHD. The decline/change in ADHD traits with age is noted in the DSM-5 (APA, 2013) as adults require five ADHD features, instead of six, to receive a clinical diagnosis of the condition. Dr. Climie commented: “Gradually, strategies are developed, interventions are put into place. As individuals move into the teenage years and into adulthood, there is usually less hyperactivity, and we see more of that inattentive piece. Individuals with ADHD certainly are able to develop strategies but in a bit of a different way.” Dr. Climie also emphasized that “ADHD certainly does persist into adulthood. It is not a condition that once you hit 18 or 19 years, it magically disappears.”

Prevalence of ADHD

The global prevalence of childhood ADHD is estimated at 5.29% (Polanczyk et al., 2007), and 2.58% for adults with childhood onset ADHD that persisted to adulthood (Song et al., 2021). While there are concerns about the overdiagnosis of ADHD, a review of the prevalence of this condition over three decades revealed that this number has remained stable, and attributed the increase in diagnosis rates to improved service accessibility and awareness (Polanczyk et al., 2014). Canadian estimates of ADHD vary based on age range, sex, and province (Espinet et al., 2022). One study of individuals between 20 and 64 years of age, estimated a national prevalence rate of 2.9% (Hesson & Fowler, 2018). Across the five provinces of Alberta, Manitoba, Newfoundland and Labrador, Ontario, and Quebec, an 8.6% prevalence of ADHD was noted in ages 4-17 years (Morkem et al., 2020).

ADHD, like autism, is overrepresented in males compared to females, with 12.9% of males between 2 to 17 years receiving a diagnosis of ADHD versus 5.6% of females (Danielson et al., 2018). “We see about three boys for every girl that is diagnosed, although I think that there is certainly an underdiagnosis for females. In moving into adulthood, we see the male/female ratio becoming closer to one-to-one. That gives us an indication that maybe we are not as good at identifying females when they are younger” said Dr. Climie. Some of the potential explanations for this discrepancy may be a lack of awareness regarding female presentation of ADHD (Mowlem et al., 2019a), and clinical diagnostic criteria having a sex/gender-specific bias (Mowlem et al., 2019b).

ADHD in girls can look different than ADHD in boys (Gershon, 2002); girls may experience more challenges with their emotions (Mowlem et al., 2019a; Nøvik et al., 2006). This more subtle presentation may lead to less diagnostic referrals to be made for females. A discrepancy was found between parents’ subjective assessment of their female (assigned female at birth) child’s level of hyperactivity and objective scales, with parents under-rating these features (Mowlem et al., 2019a). Given that ADHD is categorized as a childhood disorder, parents, guardians, and teachers are typically the first to notice and report ADHD traits in children; however, they may be more familiar with a ‘high-energy male’ presentation (Mowlem et al., 2019a).

Reflecting these differences, more awareness and education are needed on female ADHD features (Gershon, 2002). One hypothesis suggests that diagnostic criteria are less sensitive to female presentation of ADHD (Mowlem et al., 2019b). Females with prominent hyperactivity/impulsivity and conduct challenges were more likely to be diagnosed, suggesting that females with ADHD that do not present with these “externalizing behaviours” may be missed (Mowlem et al., 2019b).

Interventions for ADHD

Treatment options for ADHD include both medication and non-pharmacological options (Abraham et al., 2022). Pharmacological interventions mainly use a class of medications called psychostimulants to regulate the chemical messengers in the brain (Abraham et al., 2022). While medications are effective in decreasing the impacts of core features of ADHD, they are not recommended for children ages six years and younger (Abraham et al., 2022; Feldman et al., 2018), and it is important to note that medication cannot teach skills.

A suggested first treatment for preschool children with ADHD is behavioural therapy also involving parents (Charach et al., 2013). Some other non-pharmacological interventions include: psychoeducation, behavioural peer interventions, cognitive training, classroom management techniques, implementing daily report cards for task completion, organizational skills training, EEG neurofeedback, and exercise (Feldman et al., 2018); however, conclusions about the evidence related to these approaches and their outcomes go beyond the scope of this toolkit, inviting further examination of various approaches and outcomes. The Canadian Paediatric Society recommends nonpharmacological interventions to be “individualized, based on specified treatment goals” and “be appropriate for the child’s or youth’s age and stage,” take into account co-occurring conditions, and be “acceptable to and feasible for the patient, family, and schoolteachers” (Feldman et al., 2018, p. 462).

ADHD may present with other co-occurring conditions; one study found more than half of children with ADHD had a co-occurring mental health or developmental condition (Feldman et al., 2018). Another study found that about one-third of children with ADHD had one co-occurring condition, 16% had 2, and 18% had 3 or more; the most commonly-reported were learning disabilities, conduct disorder, anxiety, depression, and speech challenges (Larson et al., 2011).

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iii) Co-occurring Autism and ADHD

Prior to the DSM-5 (APA, 2013), a dual clinical diagnosis of autism and ADHD (henceforward denoted by autism+ADHD) was not allowed for, despite individuals often presenting with traits of both conditions. A dual diagnosis may now be given “when criteria for both ADHD and autism spectrum disorder are met” (APA, 2022). Autism+ADHD is not a separate condition but rather a combination of both, as there are shared features (Yamawaki et al., 2020). Dr. Climie explained: “Now it has become more recognized that neurologically there are overlaps between autism and ADHD. But there are also distinctions between what an ADHD profile and an autism profile would look like.” Clinicians are responsible for investigating whether the features and challenges experienced by individuals best fit an autism or ADHD diagnosis, or if a dual diagnosis would be appropriate (Rommelse et al., 2018). It is important to be aware of the features of both conditions as parents of children with ADHD and undiagnosed autism were found to attribute traits commonly seen in autism to their child’s existing ADHD diagnosis (Stevens et al., 2016). Accordingly, if parents are not made aware of the features of both conditions, they may mistakenly attribute traits of the undiagnosed condition to their child’s existing diagnosis (e.g., they may assume a behaviour is related to ADHD, when it is actually related to undiagnosed autism).

Clinicians and diagnosticians use a number of tools to assist them when considering a diagnosis of autism+ADHD. These include semi-structured clinical interviews with the individual, family, and teachers; a developmental and family history; rating scales; and observational and intellectual assessments (Young et al., 2020, p 7). This multifaceted diagnostic approach “obtains detailed information about the person’s functioning spanning many years” (Young et al., 2020). Relying on one source of information may provide a biased and incorrect view of whether the features presented by an individual correspond to an autism+ADHD diagnosis. For instance, given the relatively high heritability of both conditions, family members of an individual with a suspected dual diagnosis may have undiagnosed autism or ADHD themselves, and thus view the individual’s behaviours as typical (Young et al., 2020). Furthermore, autism and ADHD rating scales are often developed with the male presentation of the condition in mind and thus, may not be the best method of assessing challenges in females (Young et al., 2020). Therefore, it is important for clinicians to use multiple diagnostic tools.

Prevalence of Autism+ADHD

A recent study from the United States reported 43.8% of children with autism also had co-occurring ADHD, while 13.9% of those with ADHD had co-occurring autism (Casseus et al., 2023). As explained by Dr. McCrimmon, “There are more people with an autism diagnosis that also have an ADHD diagnosis in comparison to people that have an ADHD diagnosis that also have an autism diagnosis. It seems to be a more unidirectional than bidirectional relationship.” Other studies have also noted this ‘unidirectional’ relationship, with one estimate suggesting approximately one in two children (54%) with autism also received a diagnosis of ADHD (Stevens et al., 2016) versus one in eight children with ADHD who received a diagnosis of autism (Zablotsky et al., 2020). Similar to the sex ratio in the two conditions independently, males were more likely to receive a dual diagnosis of autism and ADHD (Zablotsky et al., 2020), though one report indicated that there is no sex difference in the age of diagnosis (Tang et al., 2022). In terms of sex differences in treatment, more males with autism+ADHD received behavioural treatments, while both sexes were more likely to receive medication in comparison to individuals with a single diagnosis of autism (Casseus et al., 2023).

Difference in the age of diagnosis was noted between individuals with autism+ADHD in comparison to those with either one of the conditions (Casseus et al., 2023; Sainsbury et al., 2022; Stevens et al., 2016; Zablotsky et al., 2020). Children who had a dual diagnosis were older than those with a single diagnosis of autism (Casseus et al., 2023; Zablotsky et al., 2020), with the average age of a dual diagnosis being over 6 years versus 2.5 year for autism alone (Stevens et al., 2016). On the contrary, children with a dual diagnosis were younger than those with a single diagnosis of ADHD (Zablotsky et al., 2020). These results suggest that among individuals with autism+ADHD, the diagnosis of co-occurring ADHD is earlier while the diagnosis of co-occurring autism is delayed when compared to individuals with ADHD or autism alone (Sainsbury et al., 2022). Compared to parents of children with a single diagnosis of autism, parents of children with a dual diagnosis reported having developmental concerns and seeking support for autism five to six months later on average (Stevens et al., 2016). Delay in diagnosis could also lead to a delay in receiving necessary supports.

Interventions for Autism+ADHD

Two broad categories of supports available for individuals with autism+ADHD are nonpharmacological and pharmacological interventions. A clinical guideline developed for the assessment and support of autism+ADHD identified that individuals with a dual diagnosis may benefit from various types of nonpharmacological approaches (Young et al., 2020). Furthermore, this guide emphasized that interventions must be individualized based on needs, and ensure that “individuals and/or parents/carers have realistic expectations of [their] child’s abilities and what can be achieved by interventions” (Young et al., 2020, p 12). Some of the nonpharmacological supports discussed in this guideline include psychoeducation, parenting support, psychological interventions, behavioural and environmental interventions, education/classroom-based interventions, and career/vocational training. The guideline recommended support interventions to be “integrated into a comprehensive care plan” and shared with the individual, their family members as well as all members of the care team to ensure program consistency (Young et al., 2020, p 13). Important questions to consider emerge such as what do people with dual diagnoses feel they need, and what are their perspectives?

The purpose of psychoeducation is to provide knowledge and awareness about autism, ADHD, and autism+ADHD to individuals, families, and educators (Young et al., 2020). Topics covered in psychoeducational programs may include traits and features of each condition, co-occurring challenges, types of supports and interventions available, and how to manage changes such as shifts in school or transition to adult services (Young et al., 2020). The guideline recommended psychoeducation programs to have a lifespan approach and be structured in a way that best suits the availability and needs of families (Young et al., 2020). Psychological support is especially important in this population as individuals with autism+ADHD are more likely to present with co-occurring mental health issues (Clark & Bélanger, 2018; Casseus et al., 2023).

Parents/caregivers of individuals with autism+ADHD can also benefit from targeted interventions of support. These “parenting interventions” are created to support parents/caregivers (“parent/carer support intervention”) or help them better support their child (“parent/carer mediated interventions”) (Young et al., 2020, p 14). Such resources can help parents/caregivers feel less isolated, and address environmental issues, with consideration for how individuals can be positively supported in managing and coping with challenging realities.

Individuals with co-occurring conditions may experience academic struggles in educational settings (Young et al., 2020). A few recommendations for educational interventions include providing general education on autism+ADHD traits and learning challenges to school staff and teachers, better recognizing and accommodating the sensory needs of individual students, and creating a personalized education plan (PEP) (Young et al., 2022). A PEP can be constructed with the help of the individual, parents and team members (Young et al., 2020). Dr. Climie explained that for children with autism+ADHD, “having a teacher that they feel listens to them or likes them” is important. She also recommended “making school a welcoming place where autism+ADHD students feel like they are accepted, no matter what kind of day they are having.”

Beyond school, career/vocational training for adults with autism+ADHD can help them with acquiring skills, identifying and securing employment opportunities, and ultimately living more independently (Young et al., 2020). Dr. McCrimmon highlighted the importance of employment support as “individuals with autism and/or ADHD can be very successful and valuable employees, if only employers and organizations would understand and recognize the strengths they have, and make adaptations to enable them to be successful.”

In addition to nonpharmacological approaches, medications may be a treatment option for this population. In one study sample, 72.3% of individuals with autism+ADHD were treated with pharmacotherapies while only 15.6% of individuals with autism were taking medication (Casseus et al., 2023). There is a need for more studies investigating the long-term impacts, efficacy and side effects of medication use in this population.

A decrease in the severity of ADHD features was associated with decreased parental stress, more involvement with autism interventions, and better outcomes among children with autism+ADHD (Manohar et al., 2018). “It is really hard to teach kids with ADHD skills when they are dysregulated” explained Dr. Climie, and medications can help “bring them down a notch” for parents to “work on some of the skills that need support such as social skills for children with autism.” A reviewer of this toolkit commented and asked the question, “why does medication that allows individuals to focus also decrease dysregulation? People with ADHD/autism and their families would greatly benefit from understanding why and how this works.”

When medication is deemed suitable for individuals with autism+ADHD, the Canadian Paediatric Society recommends it to be accompanied with a comprehensive treatment plan (Clark & Bélanger, 2018). This recommendation is echoed by Dr. McCrimmon who explained that “medication for ADHD can help kids be primed to learn new skills, but the medication itself does not teach them skills.”

Considering Autism+ADHD Over Time

More research is warranted into the trajectory of features in individuals with autism+ADH over time/development. Studies investigating either condition separately have found changes in autism and ADHD features with age (Shattuck et al., 2007; Gray et al., 2012; Biederman et al., 2000; Döpfner et al., 2014). Older children with autism+ADHD presented with features of anxiety and depression, suggesting screening and support for mental health as part of the support strategy for children with this dual diagnosis especially as they age and enter adolescence (Casseus et al., 2023). Children with autism+ADHD were more likely to present with other co-occurring conditions such as mental health conditions, behavioural challenges, sleep disorder, and schizophrenia (Clark & Bélanger, 2018; Casseus et al., 2023).

Research on the family/caregiver impact of supporting individuals with autism+ADHD is limited. One study on parents of children with autism+ADHD reported a higher level of parental stress in comparison to parents of children without this presentation (Miranda et al., 2015). However, a dual diagnosis was not found to correspond with added stress as parents of children with autism+ADHD reported a similar level of parenting stress to parents of children with either autism or ADHD alone (Miranda et al., 2015).

Families of children with autism+ADHD may benefit from supports. Services involving family members as well as other therapeutic support have been suggested for addressing parent/caregiver stress or challenge (Miranda et al., 2015). Such support and their impacts lie beyond the scope of this review; therefore further review is suggested, as needed, including examination of relevant resources on the AIDE Canada website and other helpful sources such as the following resource for caregivers offered by the Centre for Addiction and Mental Health: Acceptance and Commitment Training (ACT) for Family Caregivers of People with Developmental Disabilities : (Po-Lun Fung et al, 2021).


While research suggests that individuals with a dual diagnosis may experience challenges, Dr. Climie noted, “there are a lot of children on the autism spectrum with ADHD that are doing really well in aspects of their life.” She emphasized the importance of individuals with dual diagnoses “finding their path and recognizing things that they do well.” She advocated balance and a “strengths” focus as “continually focusing on the deficits can be very difficult whereas also focusing on what individuals with autism+ADHD are passionate about and strong at, will bring more balance in their lives.” The same sentiments were echoed by Dr. McCrimmon who asserted, “there are a lot of individuals that I have either diagnosed with autism or both (autism+ADHD) that are considered quite successful.” He referenced emerging research in the autism field that investigates “[individuals] thriving and things that people could do very well, and how they could be successful.” There seems to be “more appreciation for what success means and how we can support people to get there.”

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iv) Expert Recommendations

Dr. McCrimmon and Dr. Climie were asked to provide recommendations for a) parents of individuals with suspected or confirmed dual diagnoses of autism and ADHD, b) adults seeking a dual diagnosis, and c) service providers who work with this population.

a. Parents of Individuals with Dual Diagnoses

Dr. McCrimmon: “Unfortunately, the reality is regardless of which province or territory you are in, systems are not designed in a way to be easily navigated by parents – especially when you are working with two or more different diagnoses. But there are many community-based support agencies that may be helpful. And that will likely depend upon where is the closest major urban centre, and the kind of supports you are looking for. There are specific organizations that can help navigate services because parents can get overwhelmed in the search for services.”

Dr. Climie: “Keep fighting. Keep going. Do not accept the first ‘No’. Parents have to fight for services, but certainly they are their child's best advocate. All the time and effort they put in early on, will help as they move forward. So, keep at it.”

b. Adults Seeking a Dual Diagnoses

Dr. McCrimmon: “Adult diagnosis of autism is a very emergent topic/issue right now. Research suggests that the most frequently diagnosed population are adults on the autism spectrum. A lot of that is because when they were younger the diagnosis did not fit for them, or perhaps, when they were younger, that diagnosis did not exist. Most autism diagnoses are made in childhood, or even in adolescence, so it is not common to find clinicians that work with adults. As a result, fewer clinicians work with that population. It is not uncommon for people to have a two to three-year waitlist to try and see a clinician or a clinical team to get an autism diagnosis. This can be a big barrier to just get that one diagnosis much less try to look at autism and ADHD together…. If you are going to get a diagnosis, who you get it from can be a very important.”

Dr. Climie: “There is certainly an increase in adult women who are being identified with ADHD right now, again because 30 to 40 years ago, there was much less identification of ADHD in general, and girls can slide under the radar a little bit more. They are not up running around, they are more quiet and ‘daydream-y’, if they are on the ADHD side. We are finding that there are quite a few university-aged and older women who are recognizing that they are having difficulties in some areas. Often times, it is because their kids are being diagnosed with ADHD, and they reflect back, ‘Well wait, they are just like me. So, if my child has ADHD, what does that mean for me?’”

c. Service Providers

Dr. Climie: “One of the big pieces that needs to be addressed is sharing of relevant information between practitioners, not about individual clients, but rather about the research and this area in general. Psychoeducation has been found to be a really critical component for parents; for instance, to be able to understand “what is autism?”, “what is ADHD?”. But the same can be said about medical professionals and psychologists. They need to have greater awareness that first of all, autism and ADHD do co-occur. I am sure that they would be aware of that, but what does that look like and how might a dual diagnosis profile look? And what is a little bit different in how the various conditions present?

That also extends to the schools. With the prevalence of autism and ADHD, in a class of 20-25 kids, you are going to have one, two or three of them who likely will have these challenges whether they have a single or dual diagnosis. It is important for the teachers to be able to understand how these children’s minds work, what works for them, what ADHD and autism are, and how they can provide supports in the classroom so that they are best able to not only teach to academic success, but also support behavioral management, classroom management, and needed social skills. Another important piece that comes with that is ‘neurodiversity’. While this is acknowledged, it may not be as much in the forefront as it could be. I certainly think that ensuring teachers have opportunity for such professional development is really important.”

Dr. McCrimmon: “Even though somebody might be within a prominent discipline in this area and have a lot of practice experience, that does not mean that they have sufficient knowledge in this area. Guidelines evolve and therefore change your understanding of relevant issues and topics.”

Using a neurodiversity perspective, Brown and colleagues (2021) draw on literature to provide the following important suggestions for diagnosticians, 1) avoid deficit-based language when sharing a diagnosis, 2) consult parents and ask them about their feelings and understanding of the diagnosis, 3) build a rapport with the child and their family and disclose the diagnosis in a warm and empathetic way, 4) maintain the balance between being honest and providing hope when discussing a child’s needs and strengths, 5) discuss interventions and support as a way to improving quality of life rather than a ‘cure’, 6) take into account the role of culture and intersectional identities in how diagnosis is considered, and 7) support caregivers (Brown et al., 2021).

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v) Conclusion

Autism and ADHD are neurodevelopmental conditions with a childhood onset. Both conditions can co-occur. This brief literature review and expert input are offered in support of assisting individuals, families and service providers reflect on steps forward. The aim here is to support individuals with dual diagnoses, and nurture environments in which these individuals can optimize quality of life and thrive.

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vi) References

Abraham, A., Hui, J., Moloney, F. (2022). Psychiatry. In Y. Lytvyn & M.A. Qazi (Eds.), Toronto notes: Comprehensive medical reference and a review for the Medical Council of Canada Qualifying Exam (MCCQE) (38th ed.). Toronto Notes for Medical Students, Inc.

American Psychiatric Association. (2013). Neurodevelopmental disorders. InDiagnostic and statistical manual of mental disorders(5th ed.).

American Psychiatric Association. (2022). Neurodevelopmental disorders. In Diagnostic and statistical manual of mental disorders (5th ed., text rev.).

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