Comorbidities in Child ADHD

This article explores the range of comorbid conditions that often accompany the diagnosis of attention deficit-hyperactivity disorder (ADHD) in children.

Related articles: ADHD vs Neurotypical Brains: Implications for Therapists, Harnessing ADHD Benefits with a Neurodivergent-affirmative Approach, The Importance of Early Diagnosis in Child ADHD, Assessing and Treating ADHD.

Introduction

What does it mean, if you are a parent, teacher, or mental health helper, that a child you are dealing with has been diagnosed with attention deficit-hyperactivity disorder (ADHD)? In other articles (see recommended reading below), we have detailed many facets of this increasingly pervasive yet little understood manifestation of neurodivergence. The short answer to this question is that it means much more – i.e. is much more serious to diagnose and treat in terms of its complexity – if the child has a comorbid condition occurring with the ADHD. The longer answer is the topic of this article.

Recommended reading related to this topic:

• Neurodiversity, Neurodivergence and Being Neurotypical
• ADHD vs Neurotypical Brains: Implications for Therapists
• Harnessing ADHD Benefits with a Neurodivergent-affirmative Approach
• The Importance of Early Diagnosis in Child ADHD

Research shows a high incidence of comorbidity with ADHD

The importance – and challenge – of gaining a correct diagnosis about ADHD is underscored when we contemplate the substantial comorbidity that plagues those who have ADHD. Many conditions, as we list below, tend to co-exist with ADHD, and importantly, multiple studies report high incidence of ADHD comorbidity with other disorders.

Passmore (2014), for example, noted that when 449 children with ADHD between the ages of six and eighteen were studied, only 149 – that is, one-third of the research sample – were found not to have a comorbid condition. This means that fully 67% of the sample had an additional condition occurring, and only one in three of the children had “pure” ADHD. The comorbidity rate of internalising disorders (such as anxiety and depression) with ADHD is between 13 and 51% (Passmore, 2014; Gnanavel et al, 2019), and the rate of comorbid externalising disorders (such as oppositional defiance disorder) could be anywhere between 3 and 93% (Passmore, 2014), but is likely to be 30-50% (Gnanavel et al, 2019). Thus, as we have observed in previous articles, gaining a correct diagnosis of ADHD is complex and difficult. Let’s examine the conditions that you will want to be on the lookout for as the primary comorbidities with ADHD.

Autism spectrum disorder (ASD) and Learning disorders

A recent study involving a nationally representative sample from United States showed that, in children diagnosed with ASD, the rate of comorbidity with ADHD was 42% (Stevens et al, 2016). An earlier study had demonstrated that children and adolescents with combined ADHD and ASD have more severe symptoms across all domains and an additive severity of sleep-related difficulties (Sadah et al, 2006).

Learning disorders have a widely varying comorbidity rate and are experienced more by boys with ADHD than girls. Reports of comorbidity between ADHD and learning disorders range from 10% to 92%. This wide variance is possibly due to differences in diagnosis and discriminating between both the conditions in individual studies. A recent study demonstrated a relationship between learning difficulties and ADHD symptoms, predominantly in the inattentive type. In an earlier study, a learning disorder was present in 70% of the children with ADHD. A learning disorder in writing was two times more common (65%) than one in reading, math, or spelling (Mayes, et al, 2000; Gnanavel et al, 2016).

Oppositional defiant disorder (ODD) and conduct disorder (CD)

ODD is said to occur in 50% of cases of child ADHD and is characterised by defiance, hostility, resistance to instructions and orders, unwillingness to compromise, a tendency to push boundaries, unwillingness to accept responsibility, temper tantrums, refusal to comply with reasonable demands, vindictiveness, and nastiness.

CD, meanwhile, is a behavioural disorder often preceded by ODD and characterised by repetitive and persistent behaviour in which the basic rights of others, or major age-appropriate societal norms, are violated. There is often physical aggression against people or animals, lying and stealing, and impulsive, reckless, destructive behaviour, marked by lack of empathy for others and negative feelings and moods. CD is said to have a prevalence rate of 30% in children and adolescents with ADHD (Passmore, 2014).

The combined impact of ADHD with these externalising disorders on functioning can be profound. The higher rate of academic problems in children with these types of comorbidities – such as reading disorder, impaired verbal skills, visual motor integration, and visuospatial skills – on neuropsychological measures was documented long ago in comparisons with children without such comorbidity (Moffitt & Silva, 1988). Furthermore, children with both ADHD and ODD/CD are more likely to abuse drugs, engage in criminal behaviour, or have driving-related outcomes, and they are more likely to have adult antisocial personality disorder than children with ADHD alone (Barkley et al, 2004; Herrero et al, 2004). ADHD/CD has also been found to be associated with higher expulsion and dropout rates in school than in children with ADHD alone (Barkley et al, 1990).

Depression, bipolar disorder and anxiety

Depression is often exacerbated by many situations in the life of the child with ADHD, including tense family relationships, disrupted parent-child relationships, and a sense of incompetence. Children and adolescents with ADHD are said to have 5.5 times the risk of developing depression of children without ADHD. Because depressive disorders with ADHD typically occur several years after the onset of ADHD, some regard co-morbid depression as an outcome of ADHD-related impairments and negative environmental circumstances (also called as ADHD-related demoralisation by many authors). However, ADHD and depression have independent and distinct courses, showing that ADHD-associated depression reflects a depressive disorder and not merely demoralisation (Biederman et al, 1998; Gnanavel et al, 2016).

The rates of comorbidity between paediatric bipolar disorder and ADHD have been greater than chance findings but are dramatically different across studies. The association between these disorders appears more co-incidental than a causal relationship/predictive association. But when these two disorders co-occur, the patient will have poorer global functioning, greater symptom severity, and more additional comorbidity than for either of these disorders (Arnold et al, 2011).

Anxiety comorbidly occurs in about 30% of ADHD cases (with a range of 15 % to 35%), and is thought to occur three times more frequently in children with ADHD than in those who do not have it. In terms of neurophysiology, anxiety in ADHD may partially inhibit the impulsivity and response inhibition deficits, make working memory deficits worse, and may be qualitatively different from pure anxiety. The co-morbid condition has more negative affectivity and disruptive social behaviour and less fearful/phobic behaviour. The anxiety in ADHD may substantially change the presentation and course of the disorder (Biederman et al, 1998). The co-morbid condition is associated with more attentional problems, school phobia and mood disorders, and lower levels of social competence than either ADHD or anxiety alone. Sufficient importance should be given to assessment of anxiety symptoms while assessing and treating ADHD (Jarrett et al, 2016; Gnanavel et al, 2016; Passmore, 2014).

Tourette syndrome/tic disorders and language problems

Tourette syndrome (TS) is characterised by sudden, brief, repetitive movements that are involuntary and involve only a limited number of muscle groups. This may also include involuntary vocalisations. Both the movements and vocalisations are known as ‘tics’ and make children with ADHD more prone to angry outbursts and social problems.

In an international study on tic disorders and ADHD, the reported prevalence of ADHD in TS was 55% (Freeman, 2007). Previous studies have cited similar numbers as well (Angold et al, 1999). The other salient finding from the study was that ADHD was associated with earlier diagnosis of TS and a much higher rate of other difficulties (as we have noted above) (Spencer et al, 1999).

Language problems/communication disorder occur between 40 and 45% of the time in cases of ADHD. Frequently blurting out answers, interrupting others, and having trouble maintaining or changing conversational topics are characteristic of language or communication disorders, with a greater tendency to be disfluent.

Motor delays and substance abuse

Not always obvious, motor delays are often mistaken for child clumsiness. They can be of either gross motor skills (i.e., coordinating the large muscle groups of arms and legs) or fine motor skills (such as in handwriting) (Passmore, 2014).

Substance abuse, naturally occurring more in adolescents and adults than children, is a major concern for those who have the hyperactive subtype of ADHD or who have developed CD. Those with ADHD are at an increased risk of developing a substance abuse problem, but also linked with behaviours suggesting more severe substance misuse. The hyperactivity may mean impulsivity and less thought given to contemplating risks, while choosing immediate rewards (Passmore, 2014).

In summary, we note that ADHD has high comorbidity. The good news, however, is that many of these conditions can be managed with appropriate therapies and interventions, and even if a child or adolescent does have ADHD with comorbidity, they will not have all the conditions listed.

ADHD courses and training

With ADHD being one of the most common neurodevelopmental disorders, it is crucial for therapists to be well-trained in its nuances. Following are some ADHD courses and training that you may be interested in:

• Working with ADHD in Children and Adolescents
• Working with ADHD in Adults
• OnTrac: A CBT Based Manualised Group Program for Adolescents with ADHD

Note: These courses are accessible (on-demand) through Mental Health Academy membership. If you are not currently a member, click here to learn more and join.

Key takeaways

• ADHD has high associated comorbidity, both in terms of the range of conditions that co-occur with it and also in terms of the high percentage of those diagnosed with ADHD who have comorbidity.
• Because the criteria for diagnosis between ADHD and other conditions often overlap, diagnosis is complex and difficult.
• The comorbid conditions include both externalising disorders (such as ODD and CD) and internalising disorders (such as depression, bipolar disorder, and anxiety), along with numerous learning/language/communication difficulties and physical problems such as tic disorders and motor delays.

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