FOR: Adult ADHD is a valid condition requiring “clinical attention”!

Introduction

A recent umbrella review found the ADHD prevalence in adulthood to be 3.10% with the inattentive type being the commonest type of ADHD, followed by the hyperactive type and the combined type. ¹ Some studies have even found higher rates. While some experts see this as an actual increase in the prevalence of ADHD in adulthood, it is equally plausible that the apparent increase is predominantly due to better recognition. Expectedly, this has sparked debates among medical professionals and lay media, with some even questioning the validity of ADHD as an entity in adulthood. This article is an attempt to understand the various reasons behind considering ADHD as a valid entity across the lifespan and the apparent reasons for the increase in diagnostic rates of adult ADHD.

Neurodevelopmental Disorders as Lifelong Entities

There is enough evidence to suggest that all neurodevelopmental disorders are lifelong entities. However, until recently, it was thought that ADHD is a childhood disorder and people gradually grow out of it. Studies have shown that there is a relatively high rate of persistence of ADHD from childhood to adolescence (50%–80%) and into adulthood (35%–65%). ² These people continue to exhibit clinically significant impairments in various areas of their lives. Moreover, the core ADHD symptom structure (inattention, hyperactivity, impulsivity) remains invariant across age groups, indicating the same underlying condition persists into adulthood. ³ Clinically, this means that someone diagnosed with ADHD in childhood and adolescence often does not lose the diagnosis in adulthood, as was previously believed. Even those people who may no longer meet criteria for ADHD in adulthood continue to face a degree of impairment from their underlying subthreshold symptoms.

Robust Biological Markers

The validity of adult ADHD is backed by objective biological evidence. Brain imaging shows functional and structural differences in fronto-striatal and fronto-limbic networks, which are brain circuits essential for attention and executive control. ⁴ White matter microstructure disruptions have been observed in adults with ADHD, reinforcing the condition’s neurodevelopmental nature. ⁵ Moreover, adult ADHD has a high heritability (70%–80%), similar to childhood ADHD. ⁴ The neurophysiological markers of executive dysfunctions have also been consistently demonstrated to be similar to pediatric ADHD. ⁶

Problems with Diagnostic Manuals

The diagnostic manuals look at clusters of symptoms to make diagnoses and do not make consistent attempts to understand the functional etiology of symptoms. This has implications for disorders like ADHD, which have traditionally been thought to be childhood disorders. The older diagnostic manuals (ICD-10 and DSM-IV), therefore, focused predominantly on the childhood nature of symptoms, making it difficult for an adult to get a diagnosis of ADHD.^7,8 The manuals did not effectively recognize the changing manifestations of the same symptoms over time. This made it very difficult for an adult to get a diagnosis of ADHD later in life if it was missed in childhood. ICD-10 especially followed a very conservative approach by including only the combined type of ADHD in its classification, calling it “hyperkinetic disorder”. This made it extremely difficult for adults to meet diagnostic criteria. Moreover, a lot of children who only had inattentive symptoms were not diagnosed in countries where ICD-10 was used. DSM-IV was relatively more liberal with different subtypes of ADHD, which meant that the inattentive type of ADHD did not get missed. Both ICD-10 and DSM-IV, however, did not allow diagnosis of ADHD along with autism spectrum disorders, which again meant a lot of missed diagnoses. This has changed as both DSM-5 and ICD-11 have taken a distinctly different approach, making the diagnosis more inclusive.^9,10 A diagnosis of ADHD can now be made together with autism. Both ICD-11 and DSM-5 allow for diagnosing subtypes of ADHD, including the inattentive-only subtype. Criteria for diagnosing ADHD in adulthood have been made more inclusive with fewer symptom requirements. This is in line with a much better understanding of ADHD in the last few decades.

Gender Effects

The prevalence rates of ADHD in males have mostly been around twice that of females in most studies. However, it is now increasingly being recognized that this reported difference in prevalence may not reflect true differences and that ADHD symptoms may more often be missed in females as compared to males. ¹¹ Females present with inattentive symptoms more often than gross hyperactivity symptoms. Moreover, the hyperactivity symptoms may be more subtle in females than in males. Females are also more likely to have co-morbid anxiety and depressive symptoms. This makes it more likely to result in a missed or incorrect diagnosis. As the new diagnostic systems have made the diagnosis more inclusive, it effectively means that an increasing number of females are being diagnosed with ADHD in adulthood. This again does not reflect an actual increase in prevalence rates but rather better recognition of symptoms in this group of the population.

“Age of Onset” Criteria

DSM-IV and ICD-10 had a strict age of onset criteria where ADHD was only diagnosed if it could be demonstrated that the symptoms originated before the age of 6 years (ICD-10) or 7 years (DSM-IV). This was understandable as ADHD is a developmental disorder, and symptoms must be present in the developmental period. However, it also meant that it missed many children who had ADHD, but their symptoms were masked due to various factors in early childhood. We now know that children who are intelligent do not necessarily struggle in primary school despite having ADHD. This is because the supportive environment in primary schools, tolerance for hyperactive behaviors and the 1:1 help mostly by parents and private tutors compensate for their symptoms. The impairment only manifests in higher classes where there is a higher cognitive demand and less 1:1 support available. These children did not technically meet the age of onset criteria in the past and hence were not diagnosed. However, DSM-5 and ICD-11 have relaxed the age of onset criteria to 12 years of age. This change does not contradict the developmental nature of ADHD. Instead, it acknowledges that ADHD may not lead to impairment until later in life because of the factors discussed above. Instead, there is some evidence that even a later onset than 12 years may be considered as being consistent with ADHD. ¹²

Missed Diagnosis in Childhood

While the older diagnostic manuals (ICD-10 & DSM-IV) were still in place, a lot of young people who probably had ADHD were not diagnosed with it because of various reasons discussed above. This meant that they continued to struggle into adulthood and received a range of diagnoses in later life, including personality disorders, anxiety, depression, drug and alcohol use disorders, etc. It is well established that ADHD has high comorbidity with anxiety and depressive disorders, which pose significant challenges in clinical diagnosis. ¹³ The changes brought out in ICD-11 and DSM-5 have meant that clinicians now have the chance to relook at the difficulties these people have faced over the years. The changes brought out in ICD-11 and DSM-5 have meant that clinicians now have the chance to relook at the difficulties these people have faced over the years. As the recognition of ADHD as a valid disorder is growing, it is also leading to a better understanding and expertise among psychiatrists for diagnosing ADHD in adulthood. As expected, the catching-up job has meant a lot of new diagnoses of ADHD in adulthood. This may appear to artificially lead to a sudden surge in ADHD diagnosis in adulthood. However, this surge is short-lasting and likely to settle down once the catching-up has been done. On the other hand, a better understanding of adult ADHD will also ensure that an inappropriate diagnosis of ADHD is avoided.

Medication Response

Stimulant and non-stimulant medications like atomoxetine have proven efficacy for treating ADHD in both the pediatric and adult populations. ¹⁴ While medication response itself does not validate a diagnosis, it certainly supports it. There have been arguments that adult ADHD diagnoses have been fueled by pharmaceutical companies. However, this argument is not valid because a significant number of people who are diagnosed with ADHD in adulthood have already seen multiple failed trials of other medications. Often, diagnosing ADHD in them leads to a more rational use of medications and less use of polypharmacy. Another argument against medication is that stimulants can improve focus even in neurotypical people. While this may be true, it has to be differentiated from treatment response in ADHD, where medications lead to a reduction in impairment rather than performance enhancement.

The Counterargument

ADHD or any other psychiatric disorder is only diagnosed if the symptoms cause significant impairment in the life of that individual. This impairment clause means that people with milder forms of ADHD may not receive a diagnosis because of various other factors that may negate the impairment. Someone with mild ADHD who is working in a job that involves lots of physical activity, novelty and stimulation may not experience any impairment. However, if that same person chooses to go back to education, the impairment may become significant. One may argue that in the current times, more people are likely to experience an impairment because of the higher cognitive demand placed on them. Besides, people also argue that digital media in our lives makes us more distractible, which may lead people to incorrectly report symptoms of ADHD. However, environmental factors like digital environments may amplify ADHD-related challenges, but do not create symptoms themselves. The previous stigma associated with disorders like ADHD has also reduced significantly to the extent that people have actively begun to seek a diagnosis of ADHD. Despite this, a significant number of people who probably have ADHD remain undiagnosed. ¹⁵ Many adults, especially women and high-functioning individuals, are missed entirely. This gap fuels misdiagnosis (e.g., mood, anxiety, or personality disorders), underscoring the distinctiveness and unrecognized burden of adult ADHD.

Proper history and in-depth assessment using DSM-5 criteria, childhood onset confirmation, functional impairment, and ruling out differential diagnosis can ensure that mislabelling symptoms as ADHD does not happen. For this to happen, we need to first acknowledge ADHD in adulthood as a valid entity. Only then can we take steps to provide appropriate training in ADHD assessments to mental health professionals across sectors.

Conclusion

Adult ADHD is already seen as a valid clinical entity in most countries that have a well-developed psychiatric service. Through my arguments in this article, I have tried to reinforce this established concept. I hope that with the help of my arguments, Indian psychiatrists see adult ADHD as a valid clinical entity. I have discussed various factors in this article that highlight that recognition and management of ADHD in adulthood is an area of unmet need. While there may be some worries about overdiagnosis, these are clearly due to poor conceptualization of ADHD as a clinical entity. Poor conceptualization of ADHD is also the reason for missed diagnosis of ADHD and mislabelling as various other disorders. Through the arguments in this article, I propose focusing on improving expertise in assessing and managing this condition, which can have a huge impact in preventing the secondary impairments and emergence of multiple other psychiatric conditions in those affected.