Attention deficit hyperactivity disorder (ADHD) is one of the most common diagnosed neurodevelopmental disorders of the childhood. It usually benefits from well-established diagnostic methods and available therapeutic protocols, mostly implemented during childhood. Until recently, it was considered that this disorder fades during adolescence to young adulthood, with no impact on adult life, but new data confirm that ADHD symptoms persist after childhood, having clinical and psychosocial implications(1,2). Whether certain symptoms become more pronounced, or some manifestations become less intense, approximately two-thirds of the children diagnosed with ADHD have symptoms which affect their everyday activity later on in adulthood(3).
Despite the fact that there is multiple evidence that diagnosing and treating adults with ADHD delivers major benefits(4), some of the mental health specialists are reserved in acknowledging this disorder, probably because historically it has been categorized as being a childhood disorder, which is naturally outgrown. In 2015, Global Burden of Disease Study(5), which included ADHD and conduct disorders, concluded that these disorders have an impact limited to the first two decades of life. However, the progression of these pathologies indicates the fact that symptoms do not diminish or disappear as suggested(6). The different clinical manifestations of ADHD, depending on age, lead to the underdiagnose of this disorder. The specific symptoms are more obvious during childhood than after adolescence. Hyperactivity and impulsivity turn into inner restlessness, organisational difficulties linked to executive functions deficits, distractibility, which can lead to the interruption of specific treatment when it is still necessary(7).
Mental health specialists who are not familiarized with the initial manifestations, with the psychopathology and comorbidities of this disorder, can establish a diagnosis of affective or personality disorder, without taking into account the neurodevelopmental path of the patient. In the general population, ADHD is considered to be a behavioural issue, and these patients are often seen as lazy, unreliable and aggressive, without taking into consideration that this is a mental health disorder which requires treatment(8).
The progress made in terms of establishing a prognosis as precisely as possible in chronic conditions, in many domains of medicine, has considerably improved targeted intervention and personalized care(9). That is why we consider it is necessary to generally recognize ADHD diagnosis in adults, to familiarize mental health specialists with the transfer and transformation of the symptoms from childhood to adulthood, to identify the methods and diagnostic available instruments and to recognize the comorbidities which can be associated. The present article aims to bring useful information regarding these topics.
Substantial efforts have been made in the last few decades all around the world, in order to identify the prevalence of this disorder which is found to be very variable. It has been considered that this is linked to geographic and demographic factors or distinct models of evaluating the symptoms in published studies, but the reason has not been entirely identified(9).
In 2000, the American Psychiatry Association estimated that between 3% and 7% of the school-age children have ADHD(10), but numerous other studies have identified the prevalence to vary between 1% and 20%(11,12). Sex ratio is M:F=2.8:1(13). The prevalence of this disorder in adults, in epidemiologic studies, is estimated to be between 2% and 5%(13), but only less than a third of these have been diagnosed in the United States of America and far less in European countries(15). It is considered that persistent forms of ADHD have higher familial distribution than those that do not persist into adulthood. ADHD is more often found in children from parents who have this diagnosis and 20% of parents who have children with ADHD have the disorder as well(16). The studies conducted on twins and adopted children indicate the fact that genetic factors have a greater importance in the aetiology of ADHD than the environmental risk factors, thus adding an argument that this disorder persists throughout the entire life. The prevalence among first-degree relatives is between 20% and 50%(17), and average heredity is estimated to be approximately 76%(18). ADHD occurs in 10-20% of people with common mental health issues, with a high rate amongst patients with addictions or personality disorders, so it is clear that the screening is really important in these high-risk populations(19).
While symptoms like hyperactivity, impulsivity and inattention are well represented in children, during adulthood these symptoms are expressed differently and subtler. Although it is possible for all symptoms presented in children to persist into adulthood, hyperactivity has a tendency of becoming less apparent during adolescence. The deficits linked to inattention such as low academic/job performances and affected structure of daily routine, which are likely to have been less obvious during childhood, can become more problematic during adulthood. It is considered that inattention symptoms persist with aging and become more important as expectations become more complex. Although the symptoms of ADHD are present in early childhood, they develop into warning signs for parents when they notice school difficulties and/or they get teachers’ observations. The difficulty of playing and engaging in leisure activities will become obvious in these children, along with the hyperkinetic behaviour like running and excessive climbing which often lead to accidents that require emergency room care.
In the following, we will try to explain in detail how childhood specific ADHD symptoms turn into maturity, depending on the areas studied in this disorder: inattention, hyperactivity, and impulsivity.
Attention deficit becomes obvious during the first year of school. The child avoids activities that require constant mental effort, shows focusing deficit during educational activities, he/she often does not write what is taught in class. The level of distractibility is high and the child looks for excuses to take brakes, interrupting homework, and thus prolonging the time allocated to homework. Attention deficits persists during adulthood. Those adults find it difficult to perform ‘boring’ tasks that are not interactive and various, and have problems maintaining focus during meetings at the work place. They do not meet deadlines for the tasks acquired at work, they ‘dream with their eyes open’, they are forgetful, lose things and are late most of the times.
Inattention often occurs as distractibility, disorganisation, boredom, need for change in routine, difficulty in making decisions, sensitivity to stress. Moreover, they experience emotional instability throughout the entire life(20). Typically, the adults diagnosed with this disorder will not find a balance before turning 30, they change or lose jobs and relationships out of boredom or by being fired.
Hyperactivity in children especially manifests in gross motor skills. They run, climb, can hardly sit along in one place, constantly moving, cannot sit at the desk during the whole class, being very energetic, they act like ‘being run by an engine’. As time passes by, in the adult years, hyperkinetic symptoms fade away, especially after turning 12-15 years old, usually continuing as an affliction of fine motor skills or a permanent restlessness. The adult with ADHD always fidgets, does not have patience to sit when he is supposed to, has difficulties in finding relaxing activities and talks excessively.
Impulsivity is the element that is usually accentuated by time. During childhood it manifests as excessive talking, interfering in other peoples’ conversations, frequent conflicts with other children, physical and verbal aggressiveness reactive to minor frustration. The child with ADHD interferes during class, disturbing the other children, he wants to be the leader when playing with other children, and that is why it is sometimes hard for him to keep friendships. As a result of the inhibition of self-adjusting mechanisms, the adult with ADHD is permanently irritable, replies expeditiously, does not wait for his turn in conversations, and easily gets into conflict with people who do not share the same opinions.
Impulsivity exhibits as impatience, impulsive purchases or risky behaviours which involve extreme sensations. These patients start new jobs or relationships following an impulse. Furthermore, ADHD symptoms can include irritability, sleep disorders as a result of physical and mental restlessness, tiredness, and use of drugs or alcohol to relieve these symptoms.
Adults suffering from ADHD are more often involved in traffic accidents, because of the impulsivity, distractibility and high need for stimulation(21). Moreover, they are more likely to be involved in other accidents like dog bites or burns. They opt for an unhealthy lifestyle: smoking, alcohol and drug abuse, risky sexual behaviours, chronic sleep disorders which lead to delayed pace, lack of structure and routine, and inadequate medical assistance(22,23). Adults with ADHD are significantly more often arrested, condemned and incarcerated compared to those who do not have this disorder, and ADHD is often diagnosed in adults in forensic psychiatry(24).
Family life is also affected by ADHD – children can also have this diagnosis given that the familial risk for this disorder is high. Adults with ADHD tend to have a negatively-influenced relationship with their children(25). Financial resources are also low because of inferior academic performances compared to those of individuals with the same cognitive abilities(26). Many of them face feelings of loneliness and they feel isolated because of their social difficulties and shame resulted from repetitive failures. Physical and mental wellbeing is situated at an inferior level even when the IQ is high(27).
Differential diagnosis versus comorbidities
ADHD clinical picture is often grafted by comorbidities. 65% of the children with ADHD have one or more comorbid disorders such as oppositional defiant disorder or conduct disorder, anxiety and mood disorders, tics or Tourette syndrome, learning disorders or pervasive developmental disorder(28). This also applies to adults with ADHD: 75% of those diagnosed with ADHD have at least one associated disorder, but the average is of three associated psychiatric disorders – mood disorders, anxiety disorders, sleeping disorders, personality disorders and other neurodevelopmental disorders(29). ADHD has also been linked to early onset of substance abuse and gambling, and these adults often have many addictions(30,31).
The symptoms of ADHD are caused by executive functions deficit in everyday activities. When evaluating an adult with ADHD, some symptoms may be easily differentiated and others can overlap with other psychiatric disorders. Firstly, it is important to take into consideration the age of symptomatology onset. A retrospective evaluation is necessary to demonstrate that ADHD elements were present during childhood. This characteristic differentiates ADHD from bipolar disorder or a personality disorder which usually develops during late adolescence or adulthood(32).
One of the most important differences is the way the examiner identifies specific symptoms. When examining children, the emphasis is placed on the information received from caregivers and teachers. In adults, however, the majority of diagnostic tools adopt the self-reporting technique. Therefore, caution is advised because retrospective reporting of symptoms from childhood can be compromised if the recollection is not accurate(33). Although it is possible to diagnose ADHD relying only on self-reporting, this can lead to the underdiagnose of the disorder. That is why it is recommended that the information reported by the patient be corroborated with the information provided by parents or relatives for childhood symptomatology, and from the partner or close friends for current symptoms.
A very important criterion in the clinical diagnosis of ADHD is a high level of impairment in everyday activities along with the symptomatology. This is essential because symptoms that are present in ADHD are distributed amongst the general population and there is no natural limit between the affected and unaffected individuals(34). Like anxiety and depression symptoms, the symptoms of ADHD are temporary identified in the majority of individuals. The core symptoms of ADHD are linked to deficient inhibitory and self-adjusting processes which interest the five executive functions in daily activities. During the evaluation, the patient’s capacity to plan and organize must be investigated along with self-motivation and ways of managing activities in relation to time.
Therefore, the disorder is discerned from normal range by the severity and persistence of the symptoms and their association with high levels of distress, as well as the risk of developing other comorbidities, such as personality disorders.
Although hyperactivity does not have an important diagnostic value in adult ADHD, the specialists can identify a permanent restlessness, the constant sensation that thoughts succeed rapidly and the need of always being busy or having an activity. These symptoms require differentiation from the flight of ideas and precipitated speech identified in bipolar disorder or schizophrenia, as the patient with ADHD does not have bizarre or irrational thoughts. Signs of hyperactivity such as restlessness and fidgeting of the limbs are often misinterpreted as marks of anxiety disorders(35).
The differential diagnosis with other disorders that affect working memory, like pervasive disorders, anxiety and depressive disorders, takes into account the episodic nature of the symptoms in these disorders. Moreover, these are not associated with damage of the inhibitory processes, an exception being the maniac episode in bipolar disorder, but the latter does not have a chronic evolution. Working memory and all the symptoms linked to deterioration of executive functions have a physiological decline, but late onset can contribute to differential diagnosis with processes of cognitive deterioration(36).
The evaluation of adults in order to establish the ADHD diagnosis is based on a comprehensive examination of the psychopathology, the identification of functional impairment, of the pervasiveness, onset age and exclusion of other diagnosis which could better explain the symptomatology. Taking into consideration the different clinical picture depending on the age of evaluation, there are differences also regarding the diagnostic methods and the way the psychiatric interview is conducted, as mentioned before.
The diagnosing of ADHD in adults takes into consideration the age of onset of the symptoms of inattention and hyperactivity/impulsivity. The differential diagnosis is necessary to exclude other disorders with similar characteristics, as well as screening for comorbidities in order to have an adequate psychotherapeutic and pharmacologic intervention.
ADHD diagnosis has criteria that can be applied to adults only in DSM‑5 and continues to be an underdiagnosed and untreated disorder, which only increases the risk of chronicity.