The Burden of Adult ADHD in Comorbid Psychiatric and Neurological Disorders

By Stefano Pallanti and Luana Salerno

This book highlights the importance of investigating for ADHD in adults with attention difficulties, poor memory and executive function impairments. The authors advocate a neurodevelopmental assessment approach in all phases of life, and explain how to perform such assessments. The identification of ADHD in adults with other psychiatric and neurological disorders will lead to a better response to treatments, and as a result reduce its social, economic and personal burden.

ADHD can no longer be considered solely a pediatric condition, as it occurs in a significant proportion of adults worldwide. However, ADHD in adults is often unrecognized and untreated. Diagnosing the disorder in adulthood is a challenge, due not only to the different clinical presentation in this phase of life, but also to the fact that other conditions may mask the symptoms. ADHD constitutes a hidden comorbidity with a detrimental impact of those affected, and a poor response (or even non-response) to several treatments.

Intended for psychiatrists, neurologists, specialists in gerontology and neuropsychology, this book is an indispensable resource for all mental health practitioners who want to optimize the treatment of patients affected by psychiatric and neurological disorders who respond poorly to standard treatments.

• Language: English
• Publisher: Springer
• Release date: Apr 22, 2020
• ISBN: 9783030390518

Book preview

© Springer Nature Switzerland AG 2020

S. Pallanti, L. SalernoThe Burden of Adult ADHD in Comorbid Psychiatric and Neurological Disordershttps://doi.org/10.1007/978-3-030-39051-8_1

1. The Socioeconomic Burden of Adult ADHD

Stefano Pallanti¹  and Luana Salerno¹

(1)

INS, INS, Istituto di Neuroscienze, Florence, Italy

Keywords

ADHDBurdenIntimate partner violenceSexually transmitted infectionsObesitySuicidality

1.1 Introduction

According to epidemiological studies, the prevalence of adult ADHD in the general population is about 2.8%, with higher estimated prevalence in both high- (3.6%) and upper-middle (3.0%) income countries than in low and lower middle (1.4%) ones [1]. In line with the new conception of ADHD as a lifespan disorder, data regarding its prevalence rate in the elderly provide evidence of its significant persistence even late in life. Indeed, it ranges between 2.8% and 4.2%, depending on the cutoff utilized (six symptoms vs. four symptoms) and still causing impairment [2–5].

A complex relationship between ADHD, technologies development, social burden and treatment has recently been hypothesized. We are living in a society of fragmented attention, where people have become obsessed with new technologies devices, in an always-connected world of social media, smartphones, tablets, and many notifications. It has become really complicated to stay focused in a world so full of distractions. We have many more situations to manage and a much easier access to opportunities that we can seize impulsively. The development of Information Technologies (IT) and, consequently, the exponential growth in the use of Internet, social networks, and online games has led to a change in the way we process information and communicate with others. We have come to give greater importance to visual communication rather than to auditory communication, and to a way of communicating that rewards the person who is fast and able to use a very limited number of characters, even if he/she formulates ambiguous or extremely superficial sentences. Giving snippets of communication quickly and frantically is considered more important than the quality of the message you want to convey, and despite the Twitter’s decision to double the number of characters from 140 to 280, the average length of a tweet is still less consisting of 50 characters (https://​bgr.​com/​2018/​02/​08/​twitter-character-limit-280-vs-140-user-engagement/​).

On average, children and adolescents aged 8–18 years old spend 7 h and 38 min a day using entertainment media, according to a Kaiser Family Foundation report released on January 2010. They do not do one thing at a time when they use IT, but are constantly busy with many simultaneous activities: social networking, watching videos, listening to music, playing games, viewing photos, exchanging instant messages, and expressing preferences (e.g., likes or dislikes). Moreover, they have more than one device: smartphones, computers, tablets, gaming devices, and all of these tools are considered essential to be in contact with others. Out of the 7 h and 38 min spent with media every day, only 2 min are dedicated to reading newspaper or magazine online (Generation M2: Media in the Lives of 8- to 18-Year-Olds Kaiser Family Foundation January 2010). It is important to emphasize that the excessive use of these devices does not only concerns teens, because even adults can no longer do without them.

Does IT cause ADHD? Could our media-saturated society contribute to or aggravate attention problems? According to Bronfenbrenner [6],

The ecology of human development is the scientific study of the progressive, mutual accommodation, throughout the life span, between a growing human organism and the changing immediate environments in which it lives, as this process is affected by relations obtaining within and between these immediate settings, as well as the larger societal contexts, both formal and informal, in which the settings are embedded. (p. 514)

In his work, Bronfenbrenner considers the influence of the environment, in terms of interacting systems, on developing human beings. Systems are intended as layers of interactions that exert their impact on the individual in a different way, from the microsystem, which is the innermost layer (i.e., the individual’s family), to the macrosystem, which is the outermost one (i.e., the cultural influences impacting on the individual’s life). Not many years ago, it has been said that the children had become more inattentive because of the time spent watching television [7, 8], and the genetic predisposition to the development of ADHD could be expressed differently according to the environmental factors influencing the brain development. Increased exposure to television would make children more capacle of performing fast-paced activities and less capable of carrying out those activities requiring concentration.

Smartphones and other mobile devices are amazing tools when used in a prudent manner, but there is evidence indicating that they can have a negative impact on users’ ability to pay attention, remember, and think [9]. In fact, new technologies have changed our way to use our attentional skills and seem to have a negative impact on our memory, and therefore on the ability to store information and use it when necessary. The new habit of taking photo using the smartphone seems to diminish our natural ability to remember what we captured from the camera [10], and the continuous flow of information from the web during an internet session constitutes a quantity of material that can be difficult to manage and store in memory, especially for those individuals, such as people with ADHD, who are less capable of filtering out unimportant information.

With the dramatic increase in the use of Internet and social media, it is possible that there is more ADHD in modern life. Smartphone use can foster both endogenous and exogenous distractions, since the user can interrupt an activity deemed boring to move his/her thoughts toward a smartphone-related activity and start interacting with the device. This drift of attention can be caused by the desire for immediate gratification; however, once the individual has shifted attention on the device, he begins to engage in a series of activities on the smartphone, extending the break taken from the original activity [11]. Exogenous distractions are caused by environmental signals that capture the individual’s attention, such as app notifications or email alerts, that can interfere with focused attention even if we try to ignore them. The simple perception of the smartphone sound or vibration is enough to distract us by reducing our ability to focus attention on what we were doing [12]. The concentration challenged by the frequent notifications may lead to the onset of ADHD-like symptoms even in those who are not affected by the disorder, with a negative impact on productivity and psychological well-being [13]. Our society is dominated by an increased use of social networks, with people more interested in posting their selfies on Instagram, Twitter, and Facebook than in what happens in their surrounding environment, a behavior that had caused several accidents and even some deaths [14]. Although the use of Internet and new technologies has allowed adults with ADHD to become more aware of their condition and to ask for help, the growing use of technological devices further amplifies their problems of attention and self-regulation. ADHD has been shown to be associated with overuse of electronic media, including Internet and video games, with a severity of ADHD specifically correlated with the amount of their use [15]. What was evident in children, that is, that symptoms of ADHD made gaming more attractive and gaming exacerbated ADHD symptoms [15], is also evident in the adults who come to our clinics, who are always with the phone in hand, checking and writing messages, and are characterized by an hyper-focused reactivity and the need for immediate reward.

It has been widely reported that there is a global trend of large increases in the prevalence and incidence of ADHD. In a Danish nationwide sample of people aged 4–65 years for the period 1995–2010, it has been found an increase in the incidence rate of ADHD diagnosis from 7.3 to 91.2 per 100,000 people [16], but in the United Kingdom, the incidence rates showed an increase from 6.9 per 100,000 population in 1998 to 12.2 per 100,000 in 2007, and a decrease to 9.9 per 100,000 by 2009 [17]. It is possible that one of the main factors of this increase is the ease with which people today (parents of children with a suspected ADHD or people who believe to have it) can have access to medical information on the web and the stories of those persons who have received an ADHD diagnosis, recognizing themselves in their stories and wanting to have a cure for their lives so full of problems. There are a lot of web pages that describe ADHD in children and adults, promoting greater awareness of this condition as well as its negative consequences on the lives of people affected. Those adults who shared their life experiences as online narratives, once started ADHD treatment showed a more positive view of themselves and of their lives, an interruption of self-blaming and the admission of the existence of some positive traits associated with ADHD [18].

Can ADHD be an advantage in some way? Adults with ADHD can do many projects simultaneously, feel comfortable with change and chaos, they may be eager to try new things and make friends. They can be multitaskers, workaholics, hypersensitive and therefore very empathetic, intuitive, and good in emergency situations, with a great sense of humor, without fear of changing their mind, very quick in the use of new technologies (also in scanning many web pages in a short space of time), easily adaptable to the new environments, able to work well under pressure, and particularly good at delegating and organizing others. From an evolutionary point of view, ADHD symptoms have been hypothesized as a result of an evolutionary mismatch, in which current environmental demands do not fit with what evolution has prepared us to cope with [19].

However, people with ADHD can also be highly suggestible and can be easily manipulated emotionally. Adults with ADHD can be more easily influenced by propaganda and fear-induced political messages, and behave accordingly without a careful analysis of the information. Our brain is organized in networks serving specific functions: the executive control network involved in planning, anticipation, and thinking in an analytical way; the default mode network that allows us to reflect on our inner experience; the salience network that helps us decide what is relevant to us in the environment and deactivates the executive control network; and the ventral attentional networks that focus our attention on what we are doing [20]. Most of the time, a normal brain is able to shift from one network to another appropriately, but this is not the case with the ADHD brain. Consequently, adults with ADHD are more prone to give excessive salience to some forms of fears induced by political propaganda (e.g., fear of immigrants, fear of the future, fear of loss status), without exerting control and filtering such information, and therefore are more at risk of being involved in acts reflecting a poor decision making.

It has been estimated that the burden of psychiatric disorders in developed countries constitutes 40% of all mental and neurological disorders, and 14% of all diseases [21], determining a total cost in European countries of approximately 432 billion euros, of which the 36% was related to direct healthcare costs, the 12% to nonmedical costs, and the 52% to indirect costs [22].

Very few studies have examined the economic impact of undiagnosed and untreated ADHD, although it has been reported that socioeconomic costs for ADHD are higher for those receiving the diagnosis in adulthood, and lower for those who received ADHD diagnosis in childhood [23]. This is due to the pervasive negative impact of ADHD in several domains of daily life and the protective effect of the treatment. ADHD also exerts its negative impact on the patients’ families, causing stress, depression, discord among members, and a poor health-related quality of life [24–26]. Indeed there is evidence (reported below) regarding a financial burden of ADHD for family members, in the form of higher healthcare costs and productivity losses [27–29].

A recent systematic review [30] conducted by selecting studies in Europe performed on children/adolescents with ADHD published from 1990 to 2013 found that ADHD annual national costs ranged between 1041 and 1529 million euros, with ADHD-related costs of 9860–14,483 euros per patient. Findings showed that although most of the costs were incurred by ADHD patients themselves, there was a substantial portion attributable to healthcare costs for family members (161 million euros) and productivity losses (143–339 millions euros).

A similar study performed in the United States reported a total annual national cost of ADHD ranging between $143 and $266 billion, with 73% of such amount due to the costs of adult patients [28]. As in Le et al. [30], also in this systematic review including studies published from 1990 to 2011, the main cost categories for children were healthcare and education, whereas for adults they were productivity and income losses; costs for family members of individuals with ADHD were also considerable, ranging from 33 to 43 billion.

We know from longitudinal studies that children with ADHD who have not received adequate treatment tend to have, in adulthood, a lower educational level, difficulty in getting and keeping a job, poor productivity due to the tendency to procrastinate and distractibility, and more working days lost than those without the disorder [31]. In a 2006 study, it has been estimated that ADHD determined an economic productivity loss ranging between $67 and $116 billion [32], much higher than economic loss caused by asthma, which has been estimated to be around $20 billion [33, 34]. Studies that have tried to monetize the burden of ADHD have estimated that children diagnosed as having ADHD will lose an average of 4486 euros/year in their future earnings due to lower wages [35].

Impairments associated with ADHD include academic failure, self-esteem problems, interpersonal relationship difficulties [36], a higher risk for injuries and traffic accidents [37], substance abuse, sexually transmitted diseases, unplanned pregnancy [38], health problems resulting from excessive cigarette consumption and improper diet (e.g., hypertension and diabetes 2). Moreover, there is evidence of higher rates of divorce and criminal offending in adults with ADHD in comparison with those without the disorder [39]. ADHD hyperactivity and impulsivity appeared to be associated with a high risk of aggression, even in intimate relations [40–42].

I remember that when my son was 8 or 9 years old, I was constantly called by the school teachers, because he was uncontrollable, made noise, provoked others, did not respect the rules. He was a smart child, they said, but unfortunately he could not think before to act. The following years, his conduct worsened: he started kitting other students and stealing in class, even from teachers. At home, life with him was complicated. He was restless, hyperactive, and when he was frustrated by a situation he could become aggressive and violent. He used to throw things at me and offended me, then he left home and came back whenever he wanted. I was scared and tried to ask for help. A psychiatrist told me that he had a mood disorder due to his father’s abandonment, a trauma to be reworked. Meanwhile, the situation was getting out of hand, at 13 he had already been rejected for two years at school, smoked a lot of cigarettes, got drunk often, and destroyed things at home if he was irritated. People around me told me I was not a good mother, but I did not understand why it was so easy for others to be parents.

One day the police came home and searched all the rooms, found drugs and I knew that my son was accused of drug dealing. He was taken to a detention center, and in that environment, so organized and predictable, he seemed to have found peace. He finished the middle school and decided to enrol in high school. Educators told me he was an example for others and rewarded him with an exit extra. Unfortunately, on that occasion he was involved in a fight and hit some persons who (he said) provoked him. He was drunk and was not aware of the situation in which he placed himself. I ask for help again, and this time the psychiatrist told me that my son had a borderline personality disorder, which was incurable. Even though I was afraid of him, even though he might have broken my nose again, or dislocated my jaw, I could not resign myself. I felt that my son had a problem, which did not allow him to think, but he was not a monster. One day I read an article on ADHD, and started crying. I went to visit my son, I spoke with educators and then with him. When he read the article, he said: Mom, he looks like me, maybe I have ADHD too. I searched the Internet for a specialist of ADHD and I brought my son to him. He was assessed and received a combined presentation diagnosis of ADHD, a prescription of a long acting methylphenidate and was assigned an ADHD coach. I do not know what happened, but when my son realized he had a disorder he changed. We found out that ADHD has a strong genetic basis, and we realized that my ex-husband also had ADHD. I am happy now as my son has a job and will soon be married. However, it is sad to know that most young offenders have undiagnosed ADHD. In consideration of the total change that my son had after the diagnosis and especially when he started the multimodal treatment, it would be necessary to train better all the health workers in order to prevent other families from suffering as we have suffered. Ms M, 55 years old, talking about her son.

Available epidemiological data show a prevalence rate of ADHD in the 26.2–40% of prisoners [43–45], and research performed in an outpatient clinic for forensic mental healthcare in the Netherlands indicated that ADHD is a very common missed diagnosis in male adults [46]. ADHD diagnosis was missed more often in those men with hyperactive/impulsive or combined ADHD presentation, with fewer symptoms of ADHD in childhood or adolescence, and in those with a comorbid mood disorder in adulthood. Even in those who received mental healthcare, the diagnosis had been missed in 42% of cases, probably for a major emphasis given to the behavior problems leading to delinquency compared to the symptoms of a chronic disorder such as ADHD.

Inattention has been associated with an increased risk for intimate partner violence [40]: inattention hinders the adequate listening to the other person, increasing couple conflicts; when it is coupled with impulsivity, the risk of aggression is very high. Intimate partner violence (IPV) perpetrated by the partner constitutes the most common type of violence against women [47]: over five million incidents caused by IPV are reported every year, nearly two million injuries, more than 550,000 of which require medical attention, and eight million paid working days lost due to IPV consequences [48]. In addition to physical injury, it is well documented that IPV is associated with mental health problems, particularly with depression and depressive symptoms [49–52]. Depression is the most frequent mental health problem affecting women, who are twice as likely as men to suffer from a depressive episode [53], with a great economic burden in terms of disability, sick leave, and healthcare costs [54].

When I fell in love with my husband in 2001, I felt lucky to be with him because he was all I wanted in a man. But the dream soon turned into a nightmare. Before we got married, I only remember a few episodes of verbal abuse, but I thought they were isolated facts. After a few months, verbal abuse worsened and episodes increased in frequency, especially when he drank alcohol. He tended to get angry about stupid things and lost control, he insulted me, threw things at me and did not stop until he saw me on the ground, in tears. After all these episodes he apologize and swore never to do it again, but he continued to hurt me. He was violent in private but extremely polite when we were in public places. I was afraid of him. When he lost his job, he started to get depressed. I accompanied him to the psychiatrist, who asked him about his life history and gave him some sheets to complete. He told him that he probably had ADHD, and that the problem with alcohol was actually a substance use disorder. My husband confessed that he abused alcohol even before our marriage, but we lived in two different cities, and it was easier to hide it. I was shocked! The psychiatrist said that we had to go back again because he wanted to perform a more comprehensive assessment, and later he prescribed medications for him. I came out of that office feeling confused, because I knew ADHD as a problem of kids who can’t sit still at school and climbe everywhere, I didn’t know it was a condition that also makes it difficult to manage emotions. He recently started medication and psychoeducation. Together we see a marriage therapist. It is difficult to regain trust, but with ADHD medication and without alcohol I am no longer afraid of my husband.

Ms C, 43 years old, talking about her husband.

Adults with ADHD have mood swings and poor self-regulation of emotions which constitute obstacles to the correct management of conflicting situation. Intimate partner violence is fostered by excessive alcohol consumption, and men with ADHD and problem drinking have a greater risk of perpetrating this type of criminal behavior [55]. ADHD is characterized by deficits in executive functions, and the lack of inhibitory control makes adults with ADHD more susceptible to the disinhibiting effects of alcohol [56], creating the conditions to behave in a violent way with the partner.

According to the Global Health Observatory (GHO) data, the global burden determined by sexually transmitted infections (STIs) is very high, since in 2012 approximately one million per day of new infections of the curable STIs (i.e., chlamydia, gonorrhea, syphilis, and trichomoniasis) were estimated. Regarding the burden of viral STIs, 417 million prevalent cases of herpes simplex virus infection and approximately 291 million women infected with human papillomavirus [57] have been estimated. Prevention and control strategies have large health benefits, since without treatment STIs can be transmitted during unprotected sexual contact, and also lead to other health problems such as pelvic inflammatory disease (PID), infertility, ectopic pregnancy, miscarriage, fetal death, and congenital infections. Although STIs appear to affect disproportionately low-income and middle-income countries, an effective prevention program should identify vulnerable population groups, regardless of the socioeconomic situation of the country of origin.

Data published in 2005 by WHO reported that around 210 million pregnancies have occurred worldwide every year, of which 87 million had not been planned. In 2008, the total number of unsafe abortions was 21–22 million worldwide and there were 22 unsafe abortions per 1000 women aged 15–44 years. Unsafe abortion caused approximately 47,000 maternal deaths, an estimate corresponding to 13% of maternal mortality in 2008. Moreover, 50% of pregnancies in the United States are unintended, and 48% of women aged 15–44 have experienced at least one unwanted pregnancy [58–60].

Undesired children are exposed to more negative experiences, are more likely to experience health issues and dropout of high school, and may exhibit delinquent behavior during adolescence [59]. A recent report performed in the United Kingdom by Development Economics regarding the Financial and Economic Impacts of Restricted Contraceptive and Sexual Health Services claimed that, between 2013 and 2020, unintended pregnancies and STIs could cost the United Kingdom between £84.4 and £127 billion, and the annual costs for the NHS related to unwanted pregnancies between 2013 and 2020 has been estimated at £662 million [61]. There is evidence indicating that ADHD teens are 10 times more likely to have an unplanned pregnancy than their peers [37].

Evidence from scientific literature indicates that individuals with ADHD present high-risk sexual lifestyles, an earlier onset of sexual activity, more sexual partners, a higher pregnancy rate, and a four times higher prevalence of sexually transmitted disease in their history than those without ADHD [62, 63]. A study performed on a sample of women from the general community found that some risky sexual behaviors were related to symptoms of inattention or hyperactivity/impulsivity [64], and another study showed that women with ADHD reported more unprotected sex not only than women without ADHD but also more than men on average [65].

While hyperactivity and impulsivity can lead to risky sexual behavior due to the inability to stop and think before to act, it is interesting to note that high ADHD symptom scores in the inattentive domain have been found to be associated with consuming alcohol before sex [64]. Alcohol consumption can increase the likelihood of engaging in risky sexual behavior due to the reduction of inhibition caused by alcohol and the consequent impaired decision-making process. Perhaps this finding could be an explanation of data indicating that the 16% of those with ADHD have sexually transmitted diseases compared to the 4% of people without ADHD [66].

According to data from a European Commission’s (EC) Eurobarometer survey, based on 26,751 interviews carried out in 2012 in 27 EU countries, smoking tobacco is a habit for the 32% of males and 24% of females, with some age-related differences: the overall prevalence is 29% among 15–24-year-olds, 37% among 25–39-year-olds, 34% among 40–54-year-olds, and 17% among those aged 55 years or over (data from European Lung white book) [67]. Tobacco smoking constitutes the main preventable cause of morbidity and mortality from a series of disease, such as lung cancer, chronic obstructive pulmonary disease (COPD), and coronary artery disease. Smoking is also a cause of asthma in childhood and adulthood, leading to a greater severity and increasing the risk of mortality. Moreover, smoking predisposes to respiratory infections, and is also a risk factor for osteoporosis, reproductive disorders, adverse postoperative events and delayed wound healing, duodenal and gastric ulcers, periodontal disease, and diabetes (European Lung White Book); cigarette smoking has been shown to induce higher serum levels of cholesterol and increase those factors facilitating a pro-thrombotic state. According to 2013 data, the total cost of respiratory disease in the EU exceeds 380 billion euro, 5.2 million disability-adjusted life years (DALYs) are lost annually at a value of 300 billion euro, over 200 billion euro are due to COPD and asthma. About 100 million people worldwide died because of tobacco use in the twentieth century and it is estimated that they will increase to 1 billion in the twenty-first century. Passive smoking has also a consistent impact, as 600,000 nonsmokers worldwide die each year and 10.9 million DALYs are lost annually due to diseases caused by exposure to secondhand smoke. The burden from smoking cost in 2009 in Europe is €544 billion. Reducing the dramatic effects of smoking as well as its economic burden requires first of all adequate prevention, by identifying those factors leading people to start smoking and develop this addiction.

Adults with ADHD present higher rates of smoking cigarettes, ranging from 35% to 55% compared to 19–40% of the general population [68–71]. Smoking in ADHD has been hypothesized as an attempt at self-medication, being perceived as a means of improving attention and cognitive performance [72, 73], as well as to attenuate emotional lability [74]. Other research indicated the existence of a link between smoking initiation and the behavioral disinhibition characterizing people with ADHD [75], and two recent meta-analyses showed a doubling of risk for nicotine use in subjects with ADHD, which was not dependent by the presence of a conduct disorder [76, 77].

…and you know …every time I have to do something, and I have to sit down and concentrate, even during a conversation with my wife, I have to go out and smoke a cigarette. It has a sort of sedative effect on me, so when I come back from that door I’m ready to face even the most boring discussion, for a while... then I have to go out and light another one. If I have an argument with my wife, I am able to smoke ten cigarettes in just over two hours.

Mr. E., 45 years old

A prospective population cohort study including more than 1800 participants from childhood to early adulthood found that the risk for most of the substance use disorders was accounted by disruptive behaviors, but only inattention had predictive power over and above behavior problems for nicotine dependence [78]. Pharmacological treatments for ADHD do not increase the risk for tobacco use as well as for other licit and illicit substances (i.e., alcohol and drug) but have shown a protective effect [79].

Obesity constitutes an important national and global public health issue, in consideration of its prevalence and economic burden. In 2014, it was estimated that 2.1 billion people, representing approximately 30% of the global population, were overweight or obese, and obesity was the cause of the 5% of the deaths worldwide [80]. In 2014, the global economic cost of obesity was around U.S. $2.0 trillion, and apart excess healthcare expenditure, obesity imposes costs also in the form of productivity losses, due to lost work days, low productivity at work, mortality, and permanent disability [81].

According to CDC, 30.3 million people had diabetes in 2015 (9.4% of the U.S. population), 23.1 million people had a diagnosis of diabetes, 7.2 million (23.8%) were not aware of having it, and type 2 diabetes accounted for 90–95% of all diabetes cases (https://​www.​cdc.​gov/​diabetes/​pdfs/​data/​statistics/​national-diabetes-statistics-report.​pdf) [82].

The 15.9% of adults with diabetes were current smokers, and 34.5% had a history of smoking at least 100 cigarettes in their lifetime, 87.5% were overweight or obese, 73.6% of them had systolic blood pressure of 140 mmHg or higher or diastolic blood pressure of 90 mmHg or higher, or they were taking drugs for controlling blood pressure. In 2015, diabetes was the seventh leading cause of death in the United States causing 79,535 deaths, with an incidence of 24.7 per 100,000 persons. Estimated cost of diagnosed diabetes in the United States, including direct and indirect costs, was $245 billion in 2012, with average medical expenditures of about $13,700 per year, 2.3 times higher than expenditures of people without diabetes.

In 2013, more than 360,000 American deaths, almost 1000 each day, were due to medical issues in which high blood pressure was a primary or contributing cause [83]. High blood pressure increases the risk of heart attacks, strokes, chronic heart failure, and kidney disease. The 33.5% of adults aged 20 and over suffered from hypertension in 2013–2014. According to data published in 2015 by CDC [84], the cost of high blood pressure is around $48.6 billion each year, and includes healthcare services, medications for treating hypertension, and missed work days.

An increasing number of studies suggest a link between ADHD and obesity/overweight: ADHD appeared to be more prevalent in studies conducted in obese children and adults than in the general population [85, 86], a higher prevalence of obesity has been observed in patients with ADHD [87–90], and childhood ADHD was associated with an increased likelihood of overweight (1.58) and obesity (1.81), even after depression was controlled [91]. In addiction, hyperactive/impulsive symptoms correlated with increasing BMI from adolescence to early adulthood [86]. The cause of the ADHD–obesity association can be multifactorial. People with ADHD often eat in a disorganized and impulsive way [92] preferring foods with less nutrient density and more total fat, and despite their hyperactive behavior they can be less persistent in exercising. Playing a sport in adulthood is something difficult: it requires planning and organization in order to fit in the duties of everyday life. Two skills that are impaired in ADHD. Other causes have been hypothesized for accounting the relationship between ADHD and overweight, as a shared genetic mechanism such as microdeletions at chromosome 11p14.1 [94], an immune or inflammatory response, or a shared intergenerational transmission of ADHD and obesity occurring via fetal-programming mechanisms [95].

In a study including a total of 4302 patients with ADHD, ADHD was significantly associated with a prior diagnosis of Diabetes type 2 (DM) [96], and a more recent longitudinal study showed an elevated incidence of type 2 diabetes in adolescents and young adults with ADHD (0.83 vs. 0.21 per 1000 person-years, P < 0.001) as well as a higher prevalence of related comorbidities: hypertension (0.3% vs. 0.2%), dyslipidemia (0.6% vs. 0.3%), and obesity (2.3% vs. 1.0%, all P < 0.001). The crude hazard ratio of ADHD for type 2 diabetes risk was 4.01 (95% CI, 3.06–5.25), and both short- or long-term use of ADHD medications were not related to the risk for type 2 diabetes [97]. It has been hypothesized the involvement of immunologic dysregulation and proinflammatory cytokine oversecretion in the ADHD-type 2 diabetes correlation, but further research is needed to test this hypothesis. Previously undiagnosed ADHD has been found in adolescents with type 1 diabetes with poor metabolic control and who had ketoacidosis more often than patients without the disorder [98]. It is expected that people with poor organizational and planning skills, such as people with ADHD, may have difficulty managing diabetes treatment, and therefore it is important to evaluate the presence of the disorder in those patients with a poor control of diabetes. Regarding high blood pressure, a significant association between three or more hyperactive–impulsive symptoms and hypertension has been found in a study population from the National Longitudinal Study on Adolescent Health [86], but such association was no longer significant after adjusting for body mass index. However, hypertension may be a consequence of ADHD because of its connections with smoking and obesity, which often characterize this kind of patients.

Traumatic brain injury (TBI) is the leading cause of death and disability in the United States, contributing to 30% of all injury deaths [99]. It has been estimated that more than 150 individuals die from injuries including TBI every day in the United States. Those who survive can suffer from its consequences, which can be different depending on the TBI severity, ranging from mild (concussion) to severe. A severe TBI exerts its impact not only on individuals but also on their families and, to a greater extent, on the society. In fact, in 2010, the economic cost of TBI, including direct and indirect medical costs, was around $76.5 billion, in comparison with the 53.9 billion estimated cost of stroke. Motor vehicle crashes and road traffic accidents are the cause of 31.8% of deaths caused by TBI, and males are more likely to have TBI than females at any age [100].

Among TBIs, mild TBI (mTBI) represents 70–90% of traumatic brain injury complications [101, 102]. According to CDC data, there are 1.5 million new cases of mild TBI each year and, therefore, it has been described as a silent epidemic [48, 102]. Estimated costs for mild TBI have been reported in a few and, unfortunately, not recent studies, and they were around $16.7 billion [103].

In terms of long-term outcomes and recovery, the most reported consequences of non-fatal TBI are executive dysfunction, mood lability, behavioral problems, and changes in personality. The latter was the greatest source of stress and burden reported by family members [104, 105].

Individuals with ADHD have a high risk of physical injuries [106–109] and the most frequent are contusions, open wounds, dislocations, strains, sprains, and fractures of the upper limbs [107, 108]. In a cohort including around 500,000 persons aged 0–64 years, after adjustment for age, sex, and socioeconomic status, subjects with ADHD had an injury rate 1.55 times greater than those without ADHD, and it was strongly associated with severe injuries [108]. There is evidence indicating a significant association between mild traumatic brain injury (mTBI) and ADHD [110]. ADHD has been recognized as an antecedent risk factor for mild TBI in student athletes, and its presence determined more protracted course of mTBI in terms of severity of concussion symptoms [111]. These data, together with evidence that young adults and adolescents with ADHD admitted to a hospital following mTBI had worse functional outcomes than those without the disorder [112], suggested that treating ADHD may have large implications for the prevention as well as recovery from mTBI.

Suicide has been reported as the second leading cause of death for people aged 25–34 years and for those aged 15–24, and the 10th leading cause for all ages [113]. In 2013, the national cost of suicides and suicide attempts in the United States was $58.4 billion, with lost productivity representing the 97.1% of this cost. However, as several studies have shown that coroners in the United States may misclassify some suicides in teens and minorities [114–117], adjustment for underreporting increased the total cost to $93.5 billion or $298 per capita, which is 2.1–2.8 times higher than in previous studies [118].

Accumulating evidence supports a positive association between ADHD and suicidality, including completed suicides, attempts, as well as ideation: the rate of previous suicide attempts in adults with ADHD was higher than in those without (16% vs. 11% [119]), more than half of the patients with ADHD had suicidal thoughts, and one-third of ADHD patients had suicidal ideation. A recent study reported that people with ADHD have a 4.1-fold higher rate of suicidal behavior (95% CI, 3.5–4.7) when compared with those without any psychiatric diagnoses. For persons with ADHD in comorbidity with other disorders, the IRR was higher yet (IRR: 10.4; 95% CI, 9.5–11.4) [120], suggesting that the presence of ADHD, as a comorbid condition, conveys an increased risk for suicide for patients with other psychiatric disorders [121, 122]. Interestingly, the assumption of methylphenidate showed to determine a reduction of suicide risk in youth with ADHD in a recent nationwide population-based cohort study [123].

So far we have reported the costs of those health problems that we know as often associated with ADHD, but there are other clinical conditions for which research is still in its infancy. For example, recently an increased interest regarding the association between fibromyalgia and ADHD emerged with some studies reporting their frequent co-occurrence [124, 125].

ADHD is now recognized as a lifelong condition, which has been found in 2.8–4.2% of individuals aged 55–85 years old [2], a prevalence rate similar to that found in adults [126]. Adults with ADHD have a 3.4-fold risk of developing dementia [127], have a higher risk of developing a Lewy Body dementia, and recently we have found a high frequency of childhood and adult ADHD symptomatology in people affected by Parkinson’s Disease and Impulse Control Disorders (ICDs) [128]. Such latter finding is noteworthy, in consideration of the already high healthcare costs for people who have Parkinson’s disease and their families [129]. Attention problems are frequently reported by people referred to a memory clinic for a suspected mild cognitive impairment, and it is not always clear if the person is suffering from a neurodegenerative disorder or ADHD that have been compensated so far but whose symptoms have exacerbated in face of new changes in life. Social costs regarding the comorbidity between MCI and ADHD are not currently available, but the accurate differentiation of these conditions is likely to make the treatment more effective, and therefore more economic.

Finally, in clinical practice, it is not uncommon to see women facing the premenopausal period who complain of some attentional and organizational difficulties, and who remember that they have already experienced in other stages of life. Often these are women with great professional ambitions who have sacrificed the idea of a traditional family in order to pursue some more stimulating goals. Or they are women who have dedicated themselves to the family and who remember the school years as a period of great frustration and anxiety, with grades that did not always reflect the hours of study spent on the books during the afternoons. The first description is typical of the combined presentation of female ADHD, while the second is that of the inattentive presentation. In both cases, these women have suffered from depression, anxiety, compulsive eating, and often need to take medications in order to sleep. Studies reported that women facing perimenopausal and early postmenopausal periods frequently complain of some cognitive impairments, particularly in the domains of organization, working memory, concentration and attention [130], but these difficulties are severe only in a minority of them [131]. The hypothesis that such minority is made up of women with undiagnosed ADHD may find support in the experimentation with lisdexamfetamine on a sample of menopausal women with cognitive decline complaints, where only women with the most severe symptoms at the baseline have shown significant improvement in attention/concentration [131].

1.2 Conclusions

ADHD is associated with worse physical health outcomes. Undiagnosed adults with ADHD can develop several coping mechanisms and compensations without being aware of their impaired functioning. It is now clear that ADHD imposes a substantial social and economic burden, not only on the healthcare system but also on justice and educational ones. But many of the consequences as well as the social costs of an untreated ADHD could be prevented if such condition is correctly identified. There is enough evidence showing that ADHD medication present robust effect sizes in reducing ADHD symptoms, which are higher than those of SSRIs and benzodiazepines [132]. ADHD treatment (pharmacological or non-pharmacological interventions, or both) has been shown to ameliorate ADHD symptomatology and reduce adverse long-term outcomes in the health, work and family domains [133, 134], but it also has an impact on the justice-related costs, as it is associated with a reduction in crime [135]. Both national and global policy recommendations should therefore focus on ensuring that health systems identify those with ADHD early on, and support its treatment. Individuals with ADHD experience several obstacles in seeking for treatment and misdiagnosis leads to increased financial expenses. Frequent visits to the health facilities without proper diagnosis lead some patient to discouragement, and do not reduce the risk for all the negative health consequences reported. As the more time passes before receiving the diagnosis of ADHD and the higher the financial expenses, it is mandatory to raise awareness about the associations that exist between ADHD and other health conditions, in order to recognize it and treat it better.

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