ADHD in adults

Author: Ulrich Brennecke
Review: Dipl.-Psych. Waldemar Zdero

ADHD does not, as was assumed until the end of the last millennium,¹ automatically end with adulthood.

ADHD persists into adulthood in around two thirds of people with ADHD. Many show changes in symptoms, while others may experience complete remission or remission with fluctuating phases. Up to 90% of persons with ADHD still have residual symptoms or significant limitations in young adulthood compared to people without ADHD. Various reasons for the persistence of ADHD into adulthood are discussed, such as a low socio-economic background, high stress levels in childhood or late traumas. One theory assumes that ADHD already exists in childhood, but is masked by coping mechanisms and becomes visible in adulthood. Late-onset ADHD, i.e. a first appearance (or at least becoming recognizable) in adulthood, is possible and can occur in up to 10% of ADHD cases, especially in women.
The symptoms of ADHD change in adults compared to children, with hyperactivity decreasing and inner restlessness, inattention and organizational problems coming to the fore.

Treatment of ADHD in adults often requires lower doses of stimulants compared to children.

• 1. Prevalence of the persistence of ADHD into adulthood
• 2. Possible reasons for the persistence of ADHD into adulthood
• 3. Late onset ADHD: first occurrence in adulthood
  • 3.1. Late diagnosis
  • 3.2. Late first occurrence (late onset)
  • 3.3. Late-Onset ADHD: late-onset or late-diagnosed ADHD?
• 4. ADHD symptoms change in adults
• 5. Treatment for adults
• 6. Remission in adulthood
• 7. ADHD in old age

1. Prevalence of the persistence of ADHD into adulthood¶

5 % of all children have ADHD (a further 5 % are suspected of having ADHD). In the USA, around 4.4 % of all adults are affected by ADHD.²³ Further studies can be found at Krause.⁴

65 %⁵ to 90 %⁶ to 100 %⁷ of people with ADHD show at least residual symptoms or significant limitations in terms of educational and professional success into young adulthood compared to non-affected people.
63.8% showed fluctuating phases of remission and recurrence during childhood and young adulthood ⁸⁹
In adulthood, people with ADHD - with altered symptoms - persist throughout their lives with - depending on the study -

• 22 %¹⁰
• 35 %⁸⁹
• 50 %¹¹
• around 66 % (which should be the most resilient)^{1213 11}
  Complete remission in adulthood is found in around 30% of children with ADHD.⁶¹¹

One study observed in adults whose previous ADHD remitted that only the symptom groups

• Executive problems
• Behavioral problems

were remitted, while

• Hyperactivity/restlessness behavior
• Planning/organizational deficits

persisted.¹⁴

A large international study even found a higher prevalence of ADHD in adults (2.8%) than in children (2.2%).¹⁵ This could be consistent with the fact that the heritability of adult ADHD is possibly lower than that of child ADHD, i.e. that the proportion of environmental influences on the development of ADHD could be higher in adults than in children.¹⁶

2. Possible reasons for the persistence of ADHD into adulthood¶

It is not possible to predict in which persons with ADHD ADHD will disappear in adulthood. Whether persons with ADHD lose their ADHD by the age of 27 is independent of

• The severity of the Disorder¹⁷
• The age at first onset of ADHD¹⁷
• The IQ of childhood¹⁷
• Behavioral problems in childhood¹⁷
• The severity of ADHD-HI, ODD or CD¹⁷
• The duration of stimulant treatment after adolescence¹⁷

There are various theories as to why childhood ADHD disappears in some adults and persists in others.

• Children with ADHD from a low socio-economic background benefited more from special school support than children from higher socio-economic backgrounds.¹⁸ In our view, this indicates that families with a low socio-economic status are less able to compensate for their children’s deficits. This is likely to apply to all mental health problems.
• A study of stress exposure in children with ADHD found that severe stress exposure in childhood and adolescence was associated with severe ADHD-HI or ADHD-I progression into adulthood, while children with low stress exposure often showed remitting ADHD (all subtypes).¹⁹ A large cohort study in Sweden confirms this²⁰
• Another study found an up to 11.8-fold increase in trauma in late-onset ADHD. Neurophysiologically, late-onset ADHD did not differ from ADHD in people with ADHD who had had it since childhood. However, the effects were significantly stronger. At the same time, 1/3 of the late-onset ADHD sufferers were no longer diagnosed with ADHD after one year.²¹ The latter could also be an indication of a high rate of misdiagnosis.
  • Puberty is associated with a strongly altered dopaminergic innervation in the PFC. The PFC is particularly vulnerable to dopaminergic stimulation during this time. This explains the fluctuating behavior of adolescents between the poles of novelty seeking and strong withdrawal. The strong dopaminergic vulnerability in this developmental phase further explains the dangers of alcohol and drug abuse or excessive media consumption. These can cause permanent disorders of the dopamine system, which increases the risk of impulsivity, addiction or psychosis.²²
    Prolonged cortical maturation in the frontoparietal network has a favorable effect on the final performance of the brain, while acceleration, e.g. through too much dopaminergic stimulation, has an unfavorable effect.²³ In both ADHD and giftedness, the maturation of the brain is slowed down.
    See ⇒ Giftedness and ADHD In the section ⇒ Differential diagnosis of ADHD in the chapter ⇒ Diagnostics
• Anxiety symptoms at the age of 15 make mental disorders in early adulthood much more likely²⁴
  • Anxiety disorder: 4.9-fold
  • Depression: 4.8-fold
  • ADHD, ASD or developmental disorder: 3.4-fold
    This could be a further indication that middle adolescence represents a second particularly vulnerable developmental window alongside early childhood.
• One theory assumes a post-maturation of brain functions. However, not every delay in brain maturation is also a sign of ADHD. In the case of giftedness, there is a delay in the development of the cortex that corresponds exactly to the delay until the first cortex thickness maximum occurs in ADHD.
  ⇒ ADHD and giftedness.
• Another theory is that certain regions of the brain take on compensatory tasks so that the child’s ADHD deficits can be corrected as a result.²⁵
• Another model assumes that certain childhood ADHD deficits persist throughout life.²⁵
• A study of adults with persistent ADHD found an imbalance between the connections in the brain within the default mode network on the one hand and those between the default mode network and the areas that support attention and cognitive control on the other. In adults whose ADHD was remitted, these differences did not exist.²⁶²⁷
• A comparison of partially remitted and non-remitted adolescents found a significantly lower activation of the vlPFC in partial remission. This improvement in vlPFC efficiency correlated with performance on a go/no-go task and was intermediate between ADHD diagnosis and normal controls.²⁸
• A gene analysis study found four genome-wide significant loci for childhood ADHD and one for late onset ADHD. Elevated polygenic risk scores for ADHD (ADHD-PRS) were found in persistent ADHD. Childhood ADHD showed greater genetic overlap with hyperactivity and autism as well as the highest burden of rare protein truncating variants in evolutionarily restricted genes. Late onset ADHD, on the other hand, showed greater genetic overlap with depression and no increased burden of rare protein-truncating variants.¹³

3. Late onset ADHD: first occurrence in adulthood¶

The term late onset describes the first occurrence of ADHD in adulthood (from mid-20s). This is to be distinguished from a diagnosis made for the first time at this age.

3.1. Late diagnosis¶

Various long-term studies show that ADHD can also be diagnosed for the first time in adulthood. Depending on the study, this occurs in 0.4% to 10% of ADHD cases. For example, a study of young adults with ADHD found that only 12.6% had already been diagnosed with ADHD in childhood²⁹

3.2. Late first occurrence (late onset)¶

One study examined 239 participants in the MTA study who had not been diagnosed with ADHD as children and 97 of whom showed ADHD symptoms as young adults:³⁰
32 also showed the subjective stress required for a diagnosis.
Of these 32, 12 had been diagnosed with ADHD by one of the diagnostic sources at the time, but not by all sources, so no diagnosis was made.
Of the remaining 21, the current symptoms of 3 resulted from substance abuse.
Of the remaining 18, 9 already had other diagnoses of other disorders. In 5 cases, the symptoms were primarily attributed to the other disorder.
Of the 13 cases whose elevated ADHD symptoms and impairments first appeared in adolescence, 7 were excluded whose symptoms were reported only by a teacher or a teacher and themselves.
This means that the study found 6 cases (2.5% of the comparison group without ADHD at the start of the study) with late onset ADHD in adolescence.
In our opinion, the study is not suitable for assessing the frequency of late onset, as it overweights the exclusion criteria. On the one hand, those were excluded in whom only one source reported ADHD symptoms as a child and, at the same time, those were excluded in whom only one source reported symptoms in adolescence. Due to this double exclusion, the result should not be used to assess the frequency of late onset.
The study does, however, reliably establish that even from the most critical point of view, there is a group of people with ADHD with a late onset in late adolescence.

Another study examined the Pelotas birth cohort of n = 5,249 individuals born in Pelotas, Brazil, in 1993 through age 18 to 19 years, with 81.3% of participants remaining in the study.³¹
At the age of 11, 393 (8.9%) were found to have ADHD. Most of the people with ADHD were male (63.9%).
At 18 to 19 years of age, 492 (12.2%) met all DSM-5 criteria (excluding age at onset). After excluding comorbidities, a prevalence of 6.3% remained (256). Whether women predominated here (according to the wording) or were in the same minority (according to the figure of 39%) is unclear to us.
Both groups had higher levels of traffic accidents, criminal behavior, incarceration, suicide attempts and comorbidities in adulthood.
In the group of 18 to
However, only 60 children (17.2%) with ADHD still had ADHD at 18 to 19, and only 60 young adults (12.6%) with ADHD had ADHD at 11.
The results indicate a discontinuity of ADHD and a possible late onset. As many as 77.4% of the people with ADHD aged 18 to 19 would not have received an ADHD diagnosis according to the strict rules of DSM 5 (ADHD must have appeared at the age of 11 or earlier). This would deny people with ADHD meaningful and effective treatment, which is not justifiable from the point of view of the medical and psychotherapeutic duty of care. Barkley therefore rightly takes the view that the symptoms must have first appeared by the time the brain is fully developed (approx. 23 years).
The authors interpret the results as an indication of the existence of two syndromes with different developmental trajectories.
In view of the fact that ADHD is a syndrome that can arise from hundreds or even thousands of different causes, we believe that the different developmental trajectories could possibly also represent different sources of environmental influence. It is conceivable that certain environmental toxins or diseases contributed at different times. To determine this, a study of several birth cohorts from different countries could be helpful

3.3. Late-Onset ADHD: late-onset or late-diagnosed ADHD?¶

Nevertheless, we are of the opinion that a first occurrence in adulthood (late onset) should be rather rare. We assume that ADHD that occurs for the first time in adulthood usually already existed beforehand and was either overlooked, misdiagnosed or covered up by intensive coping until then. This kind of coping takes a lot of energy and very few people can manage it in the long term. Once the strength has been exhausted, the coping facade collapses and the ADHD becomes visible. This particularly affects women. In adults, the gender ratio of ADHD diagnoses is (almost) balanced.³²
Women with a late diagnosis in particular suffer from the most severe symptoms and often comorbidities such as anxiety disorders or depression, which are a typical consequence of long untreated ADHD.
On the other hand, women are more susceptible to developing emotional disorders that start later (on average in adolescence), such as depression, dysthymia, various anxiety disorders or eating disorders. Sex hormones are often discussed as possible causes.³³
A high oestrogen level alleviates deficits in learning and memory.³⁴ This could possibly explain why ADHD symptoms are often not detectable in girls during their school years and only become more apparent in women from the age of 35.

Until DSM IV, the criteria for the diagnosis of ADHD stipulated that the first symptoms must have appeared by the age of 7. With DSM 5, this was increased to an age of 12 years.

Recent findings from population-based longitudinal studies suggest that in a subset of people with ADHD, ADHD symptoms only increase after childhood and they first meet the criteria for ADHD in later adolescence or early adulthood.^{353637383910294041} One study found 45% of people with ADHD who were first diagnosed as adults did not have ADHD in childhood. They showed lower hyperactivity/impulsivity symptoms and higher education. We see both as indications of a higher probability of an overlooked diagnosis in childhood with good coping skills. In addition, higher resilience is conceivable due to various protective factors.⁴²

The updated European consensus on the treatment and diagnosis of ADHD in adults from 2018⁴³ points out that many people with ADHD have a poor memory and therefore have difficulty remembering events and details of their childhood and that there are reports of adults documenting the first onset of symptoms after the age of 12.⁴⁴⁴⁵

If the age by which the first symptoms must have appeared is set at 16, 99% of people with ADHD are covered, according to one study.⁴⁶
This means that every hundredth case of ADHD still has its first symptoms after the age of 16. Assuming a prevalence of 8% for ADHD, this would mean 64,000 people in Germany, and at 5%, 40,000 people would have late-onset ADHD after the age of 16.
It is usually found that at least one symptom was highly pronounced in adolescence, which could indicate incorrect diagnosis in adolescence.⁴⁷

Another study found in a survey of young adults with ADHD that only 12.6% already had ADHD in childhood.⁴⁸ This means that ADHD could “appear” for the first time after the age of 6 or 12 (late onset) much more frequently than previously assumed. There is now clear evidence from extensive cohort studies in various countries that ADHD can also “appear” for the first time in adulthood.⁴⁹ One study showed that in children with ADHD, the symptoms disappeared in up to 95% of people with ADHD in adulthood, while a significant proportion of adults with ADHD did not “have” ADHD as children.⁵⁰ Several long-term studies over 20 to 40 years show that ADHD in children and ADHD in adults often affect separate groups of people. Moreover, in adults, gender participation was balanced, while in children there was still a male predominance. This could also indicate a separation of the groups of people.^5152535432
We do believe that ADHD usually existed earlier and was just not diagnosed - whether due to ignorance on the part of doctors or therapists, due to intensive coping (e.g. in the case of high giftedness) or due to a good structure in the parental home, which is no longer present in independent adult life. Nevertheless, some questions remain unanswered.⁵⁵
Regardless of this, it is of no use to adult persons with ADHD if they are denied treatment in adulthood due to a lack of childhood diagnosis. There are no reports that the usual treatment methods (especially stimulants) are less effective or less effective in late onset ADHD. In this respect, special observation by the attending physician may make sense, but refusing treatment would be a breach of the physician’s duty of care. We see this in particular when a doctor refuses a diagnosis in adulthood solely on the basis of a lack of primary school reports, although the symptoms show a full ADHD picture. The notoriously poor long-term memory of persons with ADHD and the ADHD-symptomatic increased disorganization, in which a retrievable storage of primary school reports by the person with ADHD himself would almost be an argument against ADHD, cannot justify a refusal of a diagnosis in such a case for this reason alone.

One publication reports that the severity of ADHD should be milder if it occurs later.³⁸ This is in contrast to reports that late-diagnosed women in particular tend to have more severe symptoms with strong comorbidity (depression, anxiety).⁵⁴
The risk of being (diagnosed with) ADHD for the first time in adulthood also appears to be related to comorbidities. (ADHD)-typical comorbidities existing in childhood seem to increase the risk of developing ADHD in old age - just as (which has been known for some time) ADHD in childhood increases the risk of developing typical comorbidities in adulthood.⁵⁶⁵⁷

A long-term study found that of 318 children with birth problems, at age 40 those who had developed ADHD as a child were only 21% ADHD, but had poorer educational attainment, more ADHD symptoms and executive problems. Those who had attention problems as a child but not full-blown ADHD had 6.6% ADHD at age 40; those who did not show attention problems as a child had 6% ADHD. Controls without birth problems had 1.6% ADHD at 40.⁵⁸ Accordingly, around 6 to 6.6 % of those children with birth problems and 1.6 % of those without birth problems could be diagnosed with ADHD for the first time at the age of 40.

A study of 488 consecutive patients admitted to a special outpatient clinic for dementia found ADHD in 7 patients who were initially suspected of having an early form of Alzheimer’s dementia. These 7 persons with ADHD of “very late onset ADHD” or “senile onset ADHD” had four characteristics in common:⁵⁹

• significantly younger (< 65 years) than the overall study population
• predominantly inattention-related symptoms
• latent manifestation
• stressful life event before the manifestation (stress experience)

4. ADHD symptoms change in adults¶

The DSM IV criteria for ADHD describe the symptoms of children and not specifically those of adults.⁶⁰
The symptoms of ADHD in adults change considerably compared to those of ADHD in children.⁶¹⁶² Hyperactivity in particular is significantly reduced. Symptoms such as inner restlessness, inability to relax and “constantly having to be active” come to the fore.

One study reports a linear decline in hyperactivity from 6 to 2.9 points between the ages of 8 and 16.⁶³ Inattention only fell from 5.8 to 4.9 points in the same period.
However, another study shows that hyperactivity - measured here using infrared movement sensors during the performance of attention tests - is a better discriminator than attention problems, even in adults. Even in people with ADHD-I, a predominantly inattentive subtype, hyperactivity / restlessness of movement was found to be significantly higher than in non-affected people.⁶⁴

Barkley has drawn up a list of typical symptoms of ADHD in adults and verified it through research. Physical hyperactivity decreases significantly, inner restlessness becomes more visible. Inattention also decreases significantly.

The following symptoms predominate in adults:

• Inattention (reduced by up to 40% compared to children)
  Attention problems decrease by up to 40% in adults compared to children and adolescents (the decrease is thus less than that of the other main symptoms).⁶⁶ These figures are taken from the data in Biedermann’s publication. We cannot understand why the specialist literature interprets them differently. However, the decline in attention problems in adults that can be read from the data is consistent with our perception (at least for some people with ADHD). One study reports a linear decline in inattention from 5.8 to 4.9 points between the ages of 8 and 16.⁶³
  Other sources, however, report an increase in inattention at the age of⁶⁷ and consistent attention problems and executive problems from working memory between the ages of 60 and 94, some of which stemmed from depression.⁶⁸
• Hyperactivity (reduced by up to 60 % compared to children)
  Hyperactivity transforms into inner restlessness in adulthood (Barkley) and decreases by up to 60% compared to children/adolescents⁶⁶⁶³ We suspect that this is not so much a transformation as that the symptoms of inner tension become more clearly visible after the hyperactivity has subsided.
• Impulsiveness (reduced by up to 60 % compared to children)
  According to various sources, impulsivity is said to decrease by up to 60% compared to children / adolescents⁶⁶⁶⁹⁶³
  Another study found no change in impulsivity with age.⁶⁷
• Emotional overreactivity (increased in adults)⁷⁰
• Affect lability⁷¹
• Disorganization⁷¹

One study found four patterns of hyperactivity and inattention between childhood and adulthood:⁷²

• Hyperactivity
  • was low, stay low
  • was high, decreased
• Inattention
  • was low, remained low
  • was high, continued to rise

Some changes can also be measured neurophysiologically.

The problems and quality of life impairments of older adults with ADHD are similar to those of younger adults with ADHD, according to a study. This suggests that there is no long-term improvement with further ageing during adulthood.⁷⁹

Reif, on the other hand, assumes that inattention decreases only slightly, while emotional dysregulation becomes stronger in adulthood.⁸⁰
We believe that emotional dysregulation is a more accepted trait in children (“immaturity”), whereas it is perceived as inappropriate in adults. We therefore wonder whether emotional dysregulation is actually increasing in adults with ADHD or whether emotional imbalance is already present in children with ADHD, but is still perceived as acceptable and therefore not as an ADHD symptom - as we suspect is the case with internal tension, which is perceived in adulthood after physical hyperactivity decreases. We want to research this in more detail.

5. Treatment for adults¶

In adults, significantly lower amounts of stimulants are usually required to correct the dopamine and noradrenaline deficit in the reinforcement system and in the dlPFC, which could be related to the fact that the excess of dopamine transporters compared to children apparently partially regresses.
A (starting) dosage of stimulants as for children would therefore be medical malpractice. Irrespective of this, stimulant treatment should always be started with dosages of 2.5 mg / below the smallest packaging dosage sizes for sensible dosing with stimulants.

6. Remission in adulthood¶

One study examined adults three times at 7-year intervals, from an average age of 34 to an average age of 47, and showed a remission rate of 5.7%.⁸¹
One individual case reported a complete remission of his clear adult ADHD-C as a result of a corona infection. After three quarters of a year, the ADHD symptoms slowly returned. It is quite conceivable that diseases alter the dopamine system. Just as certain viral diseases can be a risk for ADHD because they can trigger a dopamine and noradrenaline deficiency, this is also possible in the opposite direction.

7. ADHD in old age¶

There are few studies on the symptoms, diagnosis and treatment of ADHD in older adults.⁸²