Adult ADHD: Prevalence and Clinical Correlates in a Sample of Italian Psychiatric Outpatients

Abstract

Objective: ADHD remains a largely underdiagnosed disorder in Europe and especially in Italy. Aims of the present study were to assess the prevalence of ADHD and its clinical and demographic correlates in a large sample of Italian outpatients. Method: 634 outpatients accessing psychiatric services were assessed with the Mini-International Neuropsychiatric Interview (MINI) Plus V. 5.0.0 interview and the Adult ADHD self-report Scale Symptoms Checklist (ASRS)-V 1.1 Short Form. Patients positive to the ASRS-V 1.1 were assessed with the Diagnostic Interview for ADHD in Adults (DIVA) 2.0. Results: Of the total patients’ sample, 81 (12.8%) were positive on the ASRS-V 1.1. After performing the DIVA 2.0, 44 patients (6.9%) met the criteria for Adult ADHD. Significant clinical and demographic differences between ADHD positive and negative groups were found. Conclusion: The prevalence and correlates of ADHD comorbidity in our outpatient psychiatric population were comparable to those found in other high-income countries. Considering the prevalence of ADHD and its impact on functioning, implementing specific knowledge on this subject is needed.

Keywords

adult ADHD comorbidity epidemiology outpatients

Introduction

ADHD is a neurodevelopmental disorder characterized by high and consistent levels of inattention, hyperactivity, and impulsivity that are present before the age of 12 years. These symptoms lead to functional impairment across multiple settings, including home, school, and peer relationships. ADHD has also been shown to have long-term adverse effects on academic performance, vocational success, and social-emotional development (American Psychiatric Association [APA], 2013).

Although ADHD is a disorder usually diagnosed in children, about 15% of the patients retain the full diagnosis by the age of 25 years, with a further 50% in partial remission, indicating that around two thirds of children with ADHD continue to have impairing levels of ADHD symptoms as adults (S. J. J. Kooij et al., 2010). A recent international meta-analysis estimated the global prevalence of ADHD in adulthood to be 2.8%, ranging from 0.6% to 7.3%, depending on the country’s income level (Fayyad et al., 2017).

Comorbidity with other psychiatric disorders is frequent in patients affected by adult ADHD, ranging from 50% to 75% (Kessler, Akiskal, et al., 2006; Piñeiro-Dieguez, Balanzá-Martínez, García-García, Soler-López, & The CAT Study Group, 2016). Patients with ADHD suffer, on average, from three other psychiatric disorders (J. J. S. Kooij et al., 2012).

The prevalence of ADHD in adult patients with major depressive disorder has been estimated to be of 9.4% in the United States (Kessler, Adler, et al., 2006), while comorbidity in bipolar disorder has been reported to be about 9.5% (Nierenberg et al., 2005). The prevalence of ADHD in patients with anxiety disorders seems to be even higher, ranging from 7% to 35% depending on the observed population (Chao et al., 2008; Van Ameringen, Mancini, Simpson, & Patterson, 2011). A recent review reported a prevalence of comorbidity between ADHD and personality disorders ranging from 10% to 75% (Matthies & Philipsen, 2016). Studies conducted in patients with substance use disorders show a prevalence of ADHD in this population ranging from 20% to 30% (Goossensen et al., 2006; Schubiner et al., 2000; Wilens, 2007).

ADHD in adults also appears to be related with sleep disorders (Gau et al., 2007; Veen, Kooij, Boonstra, Gordijn, & Someren, 2010). Considering previous literature, the prevalence of adult ADHD comorbidity across the different psychiatric disorders can range from 10% to 20% (Almeida Montes, Hernández García, & Ricardo-Garcell, 2007; Nylander, Holmqvist, Gustafson, & Gillberg, 2009; Prathibha & Maurice, 2011). A recent and carefully conducted cross-sectional study investigating the presence of ADHD in adult psychiatric nonpsychotic outpatients from Austria, Belgium, Denmark, Germany, The Netherlands, Spain, Sweden, and the United Kingdom found the prevalence to be of 15.8% according to Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.; DSM-IV-TR; APA, 2000) criteria or 17.4% according to Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5; APA, 2013) criteria (Deberdt et al., 2015). Other authors report that, on average, one out of five adult psychiatric patients may suffer from ADHD (J. J. S. Kooij, 2013).

Despite the relatively high prevalence of ADHD in the adult psychiatric population, many patients still do not receive proper diagnostic assessment, even when they are routinely followed and treated by a specialist for other disorders (Ginsberg, Quintero, Anand, Casillas, & Upadhyaya, 2014). Considering that currently available treatments show established efficacy, as attested by the high effect sizes reported in literature (De Crescenzo, Cortese, Adamo, & Janiri, 2017), raising awareness and improving diagnostic precision and scientific knowledge of adult ADHD are features of important clinical relevance (Geffen & Forster, 2018).

Appropriate resources for diagnosis are especially lacking in Europe, where therapeutic protocols and molecules approved for treatment of adult ADHD also are scarce (Ramos-Quiroga, Montoya, Kutzelnigg, Deberdt, & Sobanski, 2013). Compared with other European high-income countries, Italy shows a considerably lower rate of adult ADHD diagnosis, probably due to an even more important lack of specific clinician’s knowledge, as attested from nationally representative data (Fayyad et al., 2017).

The aims of this study were to obtain a preliminary evaluation of the prevalence of ADHD in a large sample of Italian adult outpatients and to compare sociodemographic and clinical variables of psychiatric patients with and without a diagnosis of adult ADHD.

Method

Sample and Procedures

All patients accessing two outpatient services of the University Department of Mental Health of the Brescia Spedali Civili Hospital (Italy) in the period between November 2015 and March 2017 were invited to participate in this cross-sectional observational study. Patients who accepted to participate signed a written informed consent form.

The eligibility criteria were (a) age of 18 or older, (b) patient capable of reading and understanding the administered tests, and (c) patient capable of reading and understanding the written informed consent form.

The exclusion criteria were (a) age of 70 or older, (b) diagnosis of intellectual disability, and (c) diagnosis of mental disorder related to general medical condition.

All patients received a unique identification code to maintain data anonymity and patient confidentiality. All precautions were taken for the management of sensitive data, and participants were not given monetary compensation for their involvement.

The administration of psychiatric assessment scales is routinely performed in our services according to the Department rules. In particular, all patients agreeing to participate in this study were assessed using the Mini-International Neuropsychiatric Interview (MINI Plus, Version 5.0.0; Sheehan et al., 1998) to confirm the main psychiatric diagnosis and evaluate comorbidity. All patients were also administered the Adult ADHD self-report Scale Symptoms Checklist (ASRS-V 1.1) Short Form (Kessler et al., 2005) and a questionnaire designed to collect sociodemographic and clinical features. Trained psychiatrists then tested all patients with positive ASRS-V 1.1 using the Diagnostic Interview for ADHD in Adults (DIVA 2.0; J. J. S. Kooij, 2013) to confirm adult ADHD diagnosis according to DSM-IV-TR criteria (APA, 2000). Patients who tested positive both on the ASRS-V 1.1 and the DIVA 2.0 were included in the “ADHD positive” group, whereas patients who tested negative to the ASRS-V 1.1 or who were positive on the screener but negative to the DIVA 2.0 interview were included in the “ADHD negative” group.

Assessment Tools

The MINI Plus Version 5.0.0 is designed as a brief structured interview that could be used to diagnose Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; APA, 1994) psychiatric disorders. It has demonstrated its validity and reliability in comparison with other more complex tools (van Vliet & de Beurs, 2007). In the present study, the interview was administered to all enrolled patients to confirm their main clinical psychiatric diagnosis and to identify and diagnose potential comorbidity.

The ASRS-V 1.1 is a self-administered, internationally validated (Kessler et al., 2007) screening tool for adult ADHD developed by the World Health Organization. It consists of an 18-item checklist concerning adult ADHD symptoms as reported in the DSM-IV-TR. Six of these items, four concerning attention deficit symptoms and two concerning hyperactivity/impulsivity symptoms, have shown greater sensitivity and can be used as a separate screening tool, also known as ASRS-V 1.1 Short Form. Patients indicate the frequency of occurrence for each item, from 0 (never) to 4 (very often): The test can be considered positive when four or more answers are above the cutoff value. A positive screening test cannot be considered sufficient to diagnose adult ADHD, but it indicates that further diagnostic investigation is required.

The DIVA 2.0 is a validated (Ramos-Quiroga et al., 2016) structured interview for the assessment of adult ADHD according to the diagnostic criteria of the DSM-IV-TR. It consists of 18 questions (nine concerning inattentive symptoms and nine about hyperactivity/impulsivity) investigating ADHD symptoms as reported in the DSM-IV-TR. Each question is followed by concrete examples, for both childhood and adulthood, to help the patient to recognize symptoms in his or her everyday life. The DIVA interview also investigates the impact of ADHD symptoms on patient’s functioning, considering different areas. The DIVA interview should also be completed with additional data, such as the patient’s school reports, and conducted in the presence of a family member, to better evaluate the presence of ADHD symptoms during childhood and the age of onset of the disorder. This additional information is necessary to perform the retrospective evaluation required for diagnosing ADHD in adults.

Statistical Analysis

All computations were performed using the IBM SPSS Statistics (Version 22.0, IBM Corporation, Armonk, NY, USA). Comparisons were performed using the Pearson’s χ² test for categorical variables. Mean differences in continuous variables were evaluated using the independent samples t test. A p value of .05 was used to define statistical significance.

Results

Sample Characteristics

A total of 634 patients accepted to participate in the study. There were 335 (52.8%) female and 229 (47.2%) male participants. The mean age of the sample was 47.2 years (SD ± 12).

The sociodemographic characteristics of the sample are reported in Table 1.

Table 1.

Sociodemographic Features of the Sample (n = 634).

Variables	n	%
Gender
Female	335	52.8
Male	299	47.2
Education
Primary school (5 years)	46	7.3
Middle school degree (8 years)	252	39.7
Vocational school degree (11 years)	135	21.3
Secondary school degree (13 years)	141	22.2
Bachelor’s degree (16+ years)	60	9.5
Employment situation
Housewife/student	67	10.6
Unemployed/invalid/retired	304	47.9
Part-time/full-time occupation	263	41.5
Invalidity pension
No	529	83.4
Yes	105	16.6
Marriage status
Unmarried/single	283	44.6
Married/cohabiting	215	33.9
Divorced/separated	117	18.5
Widowed	19	3
Housing
Homeless	16	2.5
Lives with parents	175	27.6
Lives with partner and family	247	39
Lives in a community	5	0.8
Lives alone	191	30.1
School changes
No	504	79.5
Yes	130	20.5
School rejections
No	426	67.2
Yes	208	32.8
Job changes
No	304	47.9
Yes	330	52.1
Family history of psychiatric disorders
No	426	67.2
Yes	208	32.8

The clinical characteristics of the sample are listed in Table 2.

Table 2.

Clinical Features of the Sample (n = 634).

Variables	n°	%
Diagnostic categories
Psychotic disorders	220	34.7
Bipolar disorder	68	10.7
Depressive disorders	119	18.8
Personality disorders	149	23.5
Anxiety disorders	48	7.6
Obsessive-compulsive spectrum disorders	7	1.1
Adjustment disorders	17	2.7
Substance use disorders	5	0.8
Somatoform disorders	1	0.2
Main psychiatric diagnosis
Schizophrenia	185	29.2
Schizoaffective disorder	11	1.7
Delusional disorder	8	1.3
Psychosis, N.O.S.	11	2.5
Bipolar disorder, Type I	43	6.8
Bipolar disorder, Type II	18	2.8
Bipolar disorder, N.O.S.	7	1.1
Major depressive disorder	102	16.6
Depressive disorder, N.O.S.	13	2.1
Dysthymia	4	0.6
Generalized anxiety disorder	19	3
Social phobia	1	0.2
Panic disorder	18	2.8
Anxiety disorder, N.O.S.	10	1.6
Obsessive-compulsive disorder	6	0.9
Trichotillomania	1	0.2
Avoidant-dependent personality disorder	1	0.2
Borderline personality disorder	77	12.1
Narcissistic personality disorder	20	3.2
Histrionic personality disorder	22	3.5
Schizoid personality disorder	1	0.2
Schizotypal personality disorder	1	0.2
Personality disorder, N.O.S.	27	4.3
Adjustment disorder	17	2.7
Somatoform disorder	1	0.2
Substance use disorder	5	0.8
Psychiatric comorbidity
Present	242	38.2
Absent	392	61.8
Psychiatric comorbidity (excluding alcohol or substance use disorder)
Present	114	18
Absent	520	82
Alcohol abuse, lifetime
Present	80	12.6
Absent	554	87.4
Alcohol abuse, actual
Present	33	5.2
Absent	601	94.8
Alcohol use, lifetime
Present	427	67.4
Absent	32,6	32.6
Alcohol use, actual
Present	339	53.5
Absent	295	46.5
Substance abuse, lifetime
Present	102	16.1
Absent	532	83.9
Substance abuse, actual
Present	50	7.9
Absent	584	92.1
Substance use, lifetime
Present	204	32.2
Absent	430	67.8
Substance use, actual
Present	62	9.8
Absent	572	90.2
Tobacco smoking, lifetime
Present	410	64.7
Absent	224	35.3
Tobacco smoking, actual
Present	310	48.9
Absente	324	51.1
Suicide attempt, lifetime
Present	153	24.1
Absent	481	75.9
Sleep disorders (according to PROMIS Adult Sleep Disturbance V 1.0 Short Form)
Absent or very mild	520	82
Mild	52	8.2
Moderate	54	8.5
Severe	8	1.3

Note. N.O.S = not otherwise specified.

Prevalence of Adult ADHD

Of the total patients’ sample, 81 (12.8%) tested positive while 553 (87.2%) resulted negative on the ASRS-V 1.1 Short Form. After performing the DIVA 2.0 interview, 44 (6.9%) of the total sample met the diagnostic criteria for adult ADHD and were therefore included in the “ADHD positive” group, while 590 (93.1%) tested negative and were included in the “ADHD negative” group.

The main psychiatric diagnoses of “ADHD positive” and “ADHD negative” groups are shown in Table 3.

Table 3.

Main Psychiatric Diagnosis in “ADHD Positive” and “ADHD Negative” Patients.

Diagnostic categories	ADHD negative		ADHD positive		Total
Diagnostic categories	n°	%	n°	%	Total
Psychotic disorders	212	96.4	8	3.6	220
Bipolar disorder	64	94.1	4	5.9	68
Depressive disorders	111	93.3	8	6.7	119
Personality disorders	126	84.6	23	15.4	149
Anxiety disorders	48	100	0	0	48
Obsessive-compulsive spectrum disorders	6	93.1	1	6.9	7
Adjustment disorders	17	100	0	0	17
Substance use disorders	5	100	0	0	5
Somatoform disorders	1	100	0	0	1

Comparison Between “ADHD Positive” and “ADHD Negative” Groups

The comparisons for sociodemographic features between the groups of “ADHD positive” and “ADHD negative” patients are reported in Table 4.

Table 4.

Comparison for Sociodemographic Features Between Groups.

Variables	ADHD negative (n = 590)		ADHD positive (n = 44)		Test	p
Variables	n°	%	n°	%	Test	p
Gender
Female	308	52.2	27	61.4	χ² = 1.37	n.s.
Male	282	47.8	17	38.6
Age in years (average and SD)	47.6 (± 11.8)		41.6 (± 13.5)		t = −3.20	.001
Education
Primary school (5 years)	45	7.6	1	2.3	χ² = 6.44	n.s.
Middle school degree (8 years)	229	38.8	23	52.3
Vocational school degree (11 years)	127	21.5	8	18.2
Secondary school degree (13 years)	130	22	11	25
Bachelor’s degree (16+ years)	59	10	1	2.3
Employment situation
Housewife/student	59	10	8	18.2	χ² = 3.70	n.s.
Unemployed/invalid/retired	282	47.8	22	50
Part-time/full-time occupation	249	42.2	14	31.8
Earns an income
No	204	34.6	26	59.1	χ² = 10.6	.001
Yes	386	65.4	18	40.9
Invalidity pension
No	492	83.4	37	84.1	χ² = 0.015	n.s.
Yes	98	16.6	7	15.9
Marriage status
Unmarried/single	260	44.1	23	52.3	χ² = 4.32	n.s.
Married/cohabiting	206	34.9	9	20.4
Divorced/separated	106	18	11	25
Widowed	18	3	1	2.3
Relationship situation
Single	347	58.8	33	75	χ² = 4.46	.035
In a relationship	243	41.2	11	25
Housing
Homeless	15 2,54	2.5	1	2.3	χ² = 6.02	n.s.
Lives with parents	156	26.4	19	43.2
Lives with partner and family	233	39.5	14	31.8
Lives in a community	5	0.85	0	0
Lives alone	181	30.7	10	22.7
School changes
No	474	80.3	30	68.2	χ² = 3.71	.054
Yes	116	19.7	14	31.8
Number of changes (average and SD)	0.39 (± 0.89)		0.72 (± 1.23)		t = 2.121	.034
School rejections
No	401	68	25	59.8	χ² = 2.03	n.s.
Yes	189	32	19	43.2
Number of rejections (average and SD)	0.54 (± 0.92)		0.84 (± 1.05)		t = 1.94	.052
Job changes
No	291	49.3	13	29.6	χ² = 6.41	.011
Yes	299	58.7	31	70.4
Family history of psychiatric disorders
No	397	67.3	29	65.9	χ² = 0.035	n.s.
Yes	193	32.7	15	34.1

“ADHD positive” were younger (41.6 ± 13.5 years) than “ADHD negative” patients (47.6 ± 11.8 years) at the time of evaluation (p = .001).

Although no significant difference emerged concerning the employment status, the two groups showed a significantly different capacity of independently earning an income: Only 18/44 (40.9%) of the “ADHD positive” group independently earned money, as compared with 386/590 (65.4%) of the “ADHD negative” patients (p = .001).

The two groups differed also in relationship status: 33/44 of the “ADHD positive” group (75%) compared with only 347/590 of the “ADHD negative” patients (58.8%) were single (p = .035).

As for changes in scholastic institutions, a significant difference was found between the two groups concerning average number of school changes, with a higher rate of changes in the “ADHD positive” group (0.72 ± 1.23) compared with the “ADHD negative” group (0.39 ± 0.89; p = .034).

Finally, a significant difference emerged concerning job changes: In particular, 31/44 of the “ADHD positive” patients (70.5%) had changed job at least once in their life, while this happened only in 299/590 of “ADHD negative” patients (50.7%; p = .011).

The comparison of clinical features between the two groups is reported in Table 5.

Table 5.

Comparison for Clinical Features Between Groups.

Variables	ADHD negative(n = 590)		ADHD positive(n = 44)		Test	p
Variables	n°	%	n°	%	Test	p
Psychiatric comorbidity
Present	215	36.4	27	61.4	χ² = 10.77	.001
Absent	375	63.6	17	38.6
Psychiatric comorbidity (excluding alcohol or substance use disorder)
Present	99	16.8	15	34.1	χ² = 8.32	.004
Absent	491	83.2	29	65.9
Alcohol abuse, lifetime
Present	71	12	9	20.4	χ² = 2.63	n.s.
Absent	519	88	35	79.6
Alcohol abuse, actual
Present	28	4.8	5	11.4	χ² = 3.63	n.s.
Absent	562	95.3	39	88.6
Alcohol use, lifetime
Present	396	67.1	31	70.4	χ² = 0.20	n.s.
Absent	194	32.9	13	29.6
Alcohol use, actual
Present	317	53.2	22	50	χ² = 0.22	n.s.
Absent	273	47.3	22	50
Substance abuse, lifetime
Present	89	15.1	13	29.6	χ² = 6.34	.012
Absent	501	84.9	31	70.4
Substance abuse, actual
Present	39	6.6	11	25	χ² = 19.06	.000
Absent	551	93.4	33	75
Substance use, lifetime
Present	180	30.5	24	54.6	χ² = 10.84	.001
Absent	410	69.5	20	45.4
Substance use, actual
Present	49	8.3	13	29.6	χ² = 20.93	.000
Absent	541	91.7	31	70.4
Tobacco smoking, lifetime
Present	378	64.1	72,73	32	χ² = 1.34	n.s.
Absent	212	35.9	27,27	12
Tobacco smoking, actual
Present	287	48.6	23	52.3	χ² = 0.64	n.s.
Absente	303	51.4	21	47.7
Suicide attempt, lifetime
Present	137	23.2	16	36.4	χ² = 3.86	.049
Absent	453	76.8	28	63.6
Number of suicide attempts (Average and SD)	0.39 (± 0.92)		1.04 (± 2.12)		t = 4.02	.000

The two groups showed a highly significant difference concerning the presence of multiple psychiatric comorbidity: 27/44 of “ADHD positive” patients (61.4%) showed multiple comorbidity (i.e., two psychiatric disorders other than adult ADHD) while only 215/590 of “ADHD negative” patients (36.4%) showed comorbidity (p = .001). This difference remains significative even excluding the comorbidity with substance use disorders (p = .004).

No differences emerged between the two groups concerning present and lifetime alcohol use and abuse. Conversely, various differences emerged concerning the use and abuse of illegal substances. “ADHD positive” patients showed higher substance use, both current (29.6% vs. 8.3%, p < .001) and lifetime (54.6% vs. 30.5%, p = .001). Even considering the diagnosis of substance abuse, “ADHD positive” patients showed a higher prevalence, both present (25% vs. 6.6%, p < .001) and lifetime (29.6% vs. 15%, p = .012) compared with “ADHD negative” patients.

Another difference was observed for the history of suicidal attempts: 16/44 (36.3%) of “ADHD positive” patients attempted suicide at least once during their lifetime, compared with 137/590 (23.2%) of “ADHD negative” patients (p = .049). Moreover, the mean number of suicidal attempts was significantly higher in the “ADHD positive” group (1.04 vs. 0.39, p < .001).

Discussion

Data obtained from the present study show a prevalence of adult ADHD of 6.9% in the total sample of outpatients with various psychiatric diagnoses. Previous literature shows a slightly higher prevalence in the psychiatric outpatient population, ranging from 10% to 20% (Deberdt et al., 2015; J. J. S. Kooij, 2013). This can probably be due to the careful diagnostic evaluation performed on our sample, comprised both of a validated screening test (Kessler et al., 2007) and a validated diagnostic interview (Ramos-Quiroga et al., 2016). Despite this conservative evaluation, the prevalence of ADHD in the sample remains high and largely comparable to those reported in previous studies.

The “ADHD positive” patients in our sample are younger than the “ADHD negative” ones. This finding is consistent with the available literature, which reports a decrease in the severity of symptoms, especially those related to hyperactivity, as the patients get older (Biederman, Mick, & Faraone, 2000; Evans et al., 2013). Some authors suggest also an increasing difficulty with aging in remembering the core symptoms of ADHD, especially those concerning attention deficit, present during childhood and first adolescence (J. J. S. Kooij, 2013). For this reason, to obtain a careful diagnostic evaluation, the presence of supplemental information, such as previous school reports and the presence of a close relative during the diagnostic interview (as required by the DIVA), is of great importance.

The sample analysis showed no statistically significant difference in school achievement between “ADHD positive” and “ADHD negative” patients. This finding could be explained by the presence in the sample of a co-occurrent psychiatric diagnosis; in fact, psychiatric patients achieve, on average, a lower educational level than the general population (Breslau, Lane, Sampson, & Kessler, 2008). However, the analysis of whole data including rejections and school changes does show differences between the two groups, confirming previous findings (Murphy, Barkley, & Bush, 2002). It could be hypothesized that ADHD patients may decide more frequently to change school for a less challenging one, a strategy that may allow to reduce the attentive burden and general stress levels enough to obtain a degree otherwise not obtainable.

Compared with “ADHD negative” patients, “ADHD positive” participants are less likely to have a personal income; this finding may represent the consequence of the presence of both inattentive and behavioral symptoms in the workplace, which often lead to poor organization, failure in time managing, and relational difficulties both with peers and with superiors (Sarkis, 2014). The data concerning patients’ working status have also been confirmed through the comparison between the number of job changes in the two groups: “ADHD positive” patients show a less stable working condition, with no less than 70% changing job at least once during their life.

Although no difference in marital status was found between the two groups, a statistically significant difference was found concerning relationship status: In particular, most “ADHD positive” patients are single, a result in line with previous literature findings (Asherson et al., 2012).

In our sample, adult ADHD was diagnosed in 6.7% of patients with depressive disorders; in particular, 4.9% of patients with major depressive disorder were included in the “ADHD positive group.” This prevalence is somehow lower than that reported in the international literature (Kessler, Adler, et al., 2006), a finding that can be explained again with the strict diagnostic process adopted. The same consideration could be made for patients with bipolar disorder: In our sample, 5.9% were included in the “ADHD positive” group, a prevalence again slightly lower than that previously reported (Nierenberg et al., 2005). Among patients with a diagnosis of personality disorder, 15.4% were included in the “ADHD positive group”; the prevalence of ADHD rises to 23.4% if only borderline personality disorder is considered, confirming the relevance of this comorbidity (Matthies & Philipsen, 2016). The prevalence of ADHD in patients diagnosed with schizophrenia was only 3.6%. In fact, previous findings reported that comorbidity of ADHD and schizophrenia in adults is not a typical feature and is therefore underresearched (Donev et al., 2011).

Concerning clinical features, the “ADHD positive” group includes a higher rate of people with multiple psychiatric comorbidity; this difference remains statistically significant after excluding the diagnosis of substance or alcohol use disorder. This result is consistent with previous literature, which shows the presence of one or more psychiatric comorbidities in 50% to 75% of adult ADHD patients (Piñeiro-Dieguez et al., 2016), and an average number of three psychiatric comorbidities in adult patients suffering from ADHD (Fayyad et al., 2017).

The study indicates a more frequent presence of substance use and abuse, both current and lifetime, in “ADHD positive” patients. This result is in line with previous findings, which showed a 50% prevalence of substance use disorders in adult participants with ADHD (Biederman, Wilens, Mick, Faraone, & Spencer, 1998; Wilens, Biederman, Mick, Faraone, & Spencer, 1997).

“ADHD positive” patients showed a higher number of lifetime suicide attempts; this finding is also in line with previous literature findings, which report a correlation between ADHD diagnosis, both in childhood and in adult life, suicide attempts, and life-threatening self-harm (Furczyk & Thome, 2014).

Our findings confirm the high prevalence of ADHD comorbidity in the adult psychiatric population in Italy, comparable to that of other high-income countries (Deberdt et al., 2015). The presence of ADHD leads to significant impairment in many areas of functioning, as shown by more frequent changes of school and jobs, lower rates of patients earning an income, and higher rates of being single. Our results also suggest a worse outcome in ADHD patients, with a higher rate of multiple psychiatric comorbidity, of substance use and abuse, and of self-harmful behavior.

Assessing ADHD comorbidity could have an important impact on managing these patients in the everyday clinical practice, as ADHD is a condition that shows a good response to specific treatment (De Crescenzo et al., 2017). Considering the short time required to administer the ASRS-V 1.1 Short Form and its good reliability as a screening tool for adult ADHD (Kessler et al., 2007), its use could be recommended as a routine in the evaluation of psychiatric outpatients, even if they are followed for another psychiatric condition. This could allow to recognize in which cases further investigation is required for this frequently undiagnosed disorder and therefore to achieve a better global evaluation of the patient.

Conclusion

We found a prevalence of ADHD in adult psychiatric outpatients in an Italian psychiatric department comparable to that found in many other high-income countries.

Many clinical correlates of the diagnosis were detected, including difficulties in relevant functional areas, such as education, work and relationship status, the prevalence of comorbidities, and self-harmful behavior, in line with previous literature obtained in other countries.

These findings indicate the importance of implementing specific knowledge on this topic in clinicians and professionals, an unmet diagnostic need in Europe and especially in Italy.

Future research should focus on confirming these data in larger samples obtained from multicenter studies. Moreover, the impact of a concomitant diagnosis of ADHD in the treatment of the primary psychiatric diagnosis and that of the treatment of ADHD in these patients have to be further assessed.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Paolo Valsecchi

Author Biographies

Paolo Valsecchi, MD, is an assistant professor of psychiatry at the Department of Clinical and Experimental Sciences, University of Brescia, Italy

Gabriele Nibbio, MD, is a psychiatry resident at the Department of Clinical and Experimental Sciences, University of Brescia, Italy

Jennifer Rosa, MD, is a psychiatry resident at the Department of Clinical and Experimental Sciences, University of Brescia, Italy

Elena Tamussi, MD, is a psychiatrist collaborating with Spedali Civili Hospital of Brescia, Italy

Cesare Turrina, MD, is an associate professor of psychiatry at the Department of Clinical and Experimental Sciences, University of Brescia, Italy

Emilio Sacchetti, MD, is a professor emeritus of psychiatry at the University of Brescia, Italy

Antonio Vita, MD, is a full professor of psychiatry at the Department of Clinical and Experimental Sciences, University of Brescia, Italy, and director of the Department of Mental Health and Addictions, Spedali Civili Hospital of Brescia, Italy

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