Clinical and Functional Outcome of Childhood ADHD 33 Years Later

Abstract

Context

Prospective studies of childhood attention deficit/hyperactivity disorder (ADHD) have not extended beyond early adulthood.

Objective

To test whether children diagnosed with ADHD at mean age 8 (probands) have worse educational, occupational, economic, social, marital outcomes; higher rates of ongoing ADHD, antisocial personality disorder (ASPD), substance disorders (SD); adult onset psychiatric disorders, psychiatric hospitalizations and incarcerations, than non-ADHD comparisons, at mean age 41. To test for: positive associations between probands’ ongoing ADHD and ASPD, and SD’s; and for worse social and occupational functioning in probands without ongoing psychiatric disorders, than comparisons.

Design

Prospective, 33 year follow-up study, with blind clinical assessments.

Setting

Research clinic.

Participants

135 Caucasian males with ADHD in childhood, free of conduct disorder, and 136 male comparisons without childhood ADHD (65% and 76% of original cohort, respectively).

Main Outcome Measures

Occupational, economic, and educational attainment; marital history; occupational and social functioning; ongoing and lifetime psychiatric disorders; psychiatric hospitalizations, and incarcerations.

Results

Probands had significantly worse educational, occupational, economic, social outcomes, and more divorces than comparisons; higher rates of ongoing ADHD (22% vs 5%, p<.001), ASPD (16% vs 0%, p<.001)and SD (14% vs 5%, p<.01), but not more mood or anxiety disorders (p’s=.36 and .33). Ongoing ADHD was weakly related to ongoing SD (phi=.19, p=.04), and ASPD+SD (phi=.20, p=.04). Lifetime, probands had significantly more ASPD and SD’s, but not mood or anxiety disorders, and more psychiatric hospitalizations and incarcerations than comparisons. Relative to comparisons, psychiatric disorders with onsets at age 21 or beyond were not significantly elevated in probands. Probands without ongoing psychiatric disorders had worse social, but not occupational, functioning.

Conclusions

The multiple disadvantages predicted by childhood ADHD well into adulthood began in adolescence, without increased onsets of new disorders after age 20. Findings highlight the importance of extended monitoring and treatment of children with ADHD.

Virtually all areas of adjustment have been shown deficient in children with Attention Deficit/Hyperactivity Disorder (ADHD), whose worldwide prevalence is estimated at 5%.¹ Consequently, the long-term outcome of childhood ADHD is a major concern. Conventional wisdom held that ADHD symptoms dissipated by adolescence. However, controlled longitudinal studies documented elevated rates of ADHD and conduct disorder in adolescence, as well as multiple other dysfunctions.^2–6

Five prospective investigations followed preadolescents with ADHD into early adulthood (ages 21 to 27).^6–12 All found higher rates of ADHD symptoms and antisocial personality disorders (ASPD) than in comparisons. In early adulthood (at mean age, 25), we found a relative increase of non-alcohol-related substance disorders (SD) in probands, but only in subjects who had developed conduct disorder during adolescence.^{9, 12}

The few prospective controlled studies have not gone beyond the third decade of life. Knowledge beyond this developmental period has been inferred from clinically referred adults diagnosed with ADHD, whose reports of early ADHD symptoms relied on recall, which problematically, has limited accuracy.^{13, 14} Nevertheless, cross-sectional studies of individuals first diagnosed in adulthood indicate that ADHD occurs in adults, and also suggest associated disabilities and co-morbidities. However, such studies do not inform the frequency and range of outcomes into adulthood, since dysfunctions may attenuate over time, or new disorders may emerge. Functional impairment caused by childhood ADHD may vary through life since adults, unlike adolescents, are not as confined by standardized demands, such as those in school. Adults may modify their environment through occupational choices, and selection of significant others. Therefore, the negative consequences of ADHD may be minimized in later life. Alternatively, new or more complex adult demands may aggravate the impact of persistent ADHD.

This report presents the adult outcome, at mean age 41, of boys who, at average age 8, were diagnosed with ADHD (probands). Two previous follow-ups have been reported on this cohort. The first, a 10 year follow-up, compared the probands to non-ADHD males (comparisons) at mean age 18 (referred to as FU18),^{4, 5} the second, at mean age 25 (referred to as FU25).^{9, 12}

We hypothesized that adults, diagnosed with ADHD in childhood, have significantly worse outcome than non-ADHD comparisons with regard to: 1) educational attainment; 2) occupational level and functioning; 3) social functioning; 4) marital status (more divorced); 5) ongoing DSM-IV ADHD, antisocial personality disorder and substance disorders (SDs) (no directional hypotheses were proposed for other mental disorders, which we report); 6) psychiatric hospitalizations; 7) incarcerations; and 8) new onsets of psychiatric disorders from age 21 on. We also posited 8) positive significant associations among ongoing DSM-IV ADHD, ASPD and SD in probands. Since childhood ADHD is believed to carry long-term disadvantages, even among individuals who no longer meet criteria for the disorder,¹⁵ we hypothesized, 9) that even probands without any ongoing mental disorder at follow-up would have relatively worse occupational and social functioning than comparisons.

Methods

The study was approved by the Institutional Review Board of the NYU Langone Medical Center. Participants were informed fully of study procedures and provided signed consent.

Two groups were studied. Probands were referred by teachers because of behavior problems. Another group, identified at FU18, was judged free of ADHD in childhood (comparisons). Sample characteristics, described elsewhere,^{4, 5, 9} are summarized.

Probands

Probands were 6 to 12 year old boys (mean, 8.3±1.6 years), all referred by teachers between 1970 and 1978. They had to be rated as hyperactive by teachers, as well as by parent or clinician, have a history of behavior problems, IQ ≥85, no history of psychosis or neurological disorder. At the time, the diagnosis and treatment of hyperactive children were poorly understood. To study a relatively homogeneous syndrome, we excluded children when teachers’ referrals involved aggressive or other antisocial behaviors, or if the psychiatric assessment with parent and child indicated a pattern of antisocial activities. This approach was guided by the belief that hyperactive/impulsive disorder differed in kind from conduct disorder.

A total of 207 Caucasian boys were enrolled. Children’s clinical status was consistent with DSM-IV ADHD, combined type, since symptoms were impairing and cross-situational; teachers’ inattentive and hyperactivity/impulsivity ratings were high [rated 0–3] ¹⁶ : (means, inattentive/distractible, 2.52±0.7; restless/overactive, 2.71±0.6; excitable/impulsive, 2.34±0.9. In contrast, ratings of conduct problems were low (M=0.7±0.4),¹⁷ documenting exclusion of conduct disorder.

Comparisons

At FU18, we identified Caucasian males matched for age with probands. They had sought medical attention in the same medical center, between ages 6 and 12, for routine physical examination or acute conditions. Charts regularly noted the child’s school adjustment. Children whose chart indicated unremarkable school behavior, and whose parents’ occupation appeared to match the probands’, were selected. Parents were called, informed of the study, and asked whether any elementary school teacher had ever complained about their child’s behavior. If not, the child was recruited. Refusal rate was low, ~5%.

Current Study - Assessment at Mean Age 41

At FU41, 135/207 (65%) probands and 136/178 (76%) controls participated. Trained and closely supervised doctoral level clinical psychology candidates, blind to all antecedent data, obtained detailed information about education, employment history, occupational adjustment, marital history, family composition, living circumstances, social functioning, medical history, and psychiatric status. Informant interviews were conducted for 9/135 probands, and 7/136 comparisons who could not, or refused to, be interviewed, but consented to an informant interview.

Since FU41 included a brain scan,¹⁸ transportation was provided for subjects to come to NYU. Subjects who did not travel to New York were interviewed by telephone [24/135 probands (18%), 25/136 comparisons (18%)]. Rates of mental disorders did not differ significantly between telephone and direct interviews.

Educational and Occupational Attainment, and Function

Years of education and highest degree define educational attainment. Occupational attainment was classified following Hollingshead and Redlich¹⁹ (scaled 1–8). “Currently employed” reflects employment at follow-up. Queries included work history, i.e., jobs held, job satisfaction, work relationships, latenesses, job changes, firings. Incorporating all information, clinicians rated occupational function over the previous six months, regardless of type of employment, on an anchored scale (1, superior; 2, very good; 3, good; 4, average; 5, fair; 6, poor).

Social Functioning

We inquired about friendships, social and leisure activities. Social functioning was rated on a 6 point scale (superior to poor), as noted above.

Incarcerations

Incarceration was broadly defined as having been in a reform school or jail for one day or more (not restricted to jail sentences for convicted offenses).

Psychiatric Diagnoses

DSM-IV disorders, as well as multiple aspects of function, were assessed for the interval between FU25 and FU41 (Mean, 16 years) with the SCID-I/NP.²⁰ We designed an interview to evaluate adult ADHD symptoms, and directly related impairment.²¹ Since childhood ADHD had been established in probands, and ruled out in comparisons, ongoing ADHD was diagnosed when all clinical criteria were met, without recalled onset age, i.e., the person “often” experienced the stipulated criteria, had significant related impairment/distress, and cross-situationality.

Clinicians inquired whether each symptom cluster (inattention, hyperactivity, impulsivity) had interfered with work, home or social life. If so, probes followed for examples of interference. Impairment was rated 1 to 5. Scores of 3–5 were considered to indicate significant impairment (3=Definitely a problem at times, or somewhat of a problem on numerous occasions, with some interference in functioning, or clinically significant distress; 5=Symptom characterizes functioning and is a major problem).

Clinicians formulated definite and probable DSM-IV diagnoses. They wrote narratives summarizing overall function, clinical picture, and justified diagnoses. Definite diagnoses indicate that DSM-IV criteria were fulfilled. Probable diagnoses indicate that the person reported fewer symptoms than required, but reported impairment or distress specifically related to the symptoms (sub-threshold disorders). Ongoing ADHD, ASPD and SD were defined as occurring in the previous six months. A window of two months defined other disorders as ongoing. For ongoing disorders, we rely on definite diagnoses, so that our results may be compared to others’ who do not report “probable” diagnoses. For rates of lifetime disorders, we combined probable and definite diagnoses. This was done since retrospective self-reports may underestimate past symptoms, but there is support for their clinical significance if they caused impairment. Lifetime disorders are based on findings from all follow-ups (FU18, FU25, and FU41), and necessarily span different DSM’s. However, this applied to both probands and comparisons. Disorders with an onset during adulthood are exclusively those that were reported to have emerged de novo from age 21 on. These were generated by combining diagnoses made at the previous and current follow-ups, which regularly inquired about first onset.

Missing Subjects

Probands

Of 207 probands, 72 (35%) were lost to follow-up: 21 were not located; 13 refused; information was not obtained for 11/15 deceased; interviews were denied in 4/6 incarcerated probands; and grant support ended before 23 were evaluated. Childhood characteristics of assessed and lost probands did not differ significantly. Of the 135 probands evaluated at FU41, 97% had been assessed at FU18, and 96% at FU25 (noted in Figure 1). At FU25, probands assessed and lost to FU41 did not differ significantly on rates of ADHD, ASPD and SD.

Figure 1.

Flow of Assessed and Not Assessed Probands and Comparison Cases

Comparisons

Of 178 comparisons, 42 (23.5%) were lost to follow-up: Twenty were not located; 15 refused. Informant interviews were not obtained for 2/5 deceased comparisons; one was incarcerated; grant funds ended before four were scheduled. The evaluated comparisons tended to have higher SES (p=.07), had significantly higher IQ’s than lost comparisons at FU18 (p=.001), and tended to have lower alcohol/substance disorders (p=.10) at FU25. All comparisons (100%) who participated at FU41 had been evaluated at FU25.

Data Analyses

Group contrasts for continuous measures relied on unpaired t tests, uncorrected χ² for dichotomous variables, and Fisher’s Exact Tests when expected cell frequencies were <5. Phi coefficients provide effect sizes of χ² values. Since IQ has not previously been found to be significantly related to mental disorders, analyses were not adjusted for IQ (no relationship was noted either at FU41). Alpha was set at p≤.05, two-tailed.

Seventy five audiotapes representing multiple disorders were rated independently by SM. Kappas²² (ADHD=.95, any SD=.97, any mood=.90, any anxiety=.92) indicated high chance-corrected inter-rater reliability.

Results

Educational and Occupational Attainment

On average, probands had 2.5 fewer years of schooling than comparisons. Their relative disadvantage is well illustrated in Table 1: over 30% did not complete High School, versus 4% of comparisons, and hardly any (4%) had higher degrees, whereas 29% of comparisons did.

Table 1.

Demographics and Social and Occupational Functioning at Follow-up 41

Variable	Probands (n = 135)		Comparisons (n = 136)		t (df) or χ2	p ≤
	Mean (SD) or n (%)	Range	Mean (SD) or n (%)	Range
Age (years)	41.4 (2.9)	30–47	41.5 (3.2)	33–48	0.29 (269)	.78
Education (years)	13.3 (2.1)	8–20	15.8 (2.3)	11–20	9.52 (269)	.001
Highest Grade Completed
Less than High School	17 (13)		1 (1)		FET	.001
GED	25 (19)		5 (4)		15.16	.001
High School	32 (24)		14 (10)		8.64	.004
Some College	35 (26)		29 (21)		0.79	.39
Bachelor’s	21 (16)		47 (35)		13.02	.001
Higher Degree	5 (4)		40 (29)		32.33	.001
Hollingshead Occupational Levela	4.7 (2.0)	1–8	3.0 (1.8)	1–8	7.12 (269)	.001
SESb	3.4 (1.0)	1–5	2.4 (1.1)	1–5	8.39 (269)	.001
Employed	113 (84)		129 (95)		8.81	.01
Annual Salaryc	93,317 (158,414)	4,000–1,500,000	175,058 (224,957)	15,000–1,500,000	3.20 (217)d	.01
Mediane	60,000		100,000			.001
Occupational Functioningc,f	3.2 (1.1)	1–6	2.5 (0.9)	1–5	5.82 (240)	.001
Median	3		2
Social Functioningf	3.8 (1.3)	2–6	2.9 (1.0)	1–6	6.61 (269)	.001
Median	4		3
Marital Status
Single (Never Married)	13 (10)		13 (10)		0.01	.95
Married/Cohabiting	94 (70)		107 (79)		2.89	.10
Separated	15 (11)		12 (9)		0.4	.90
Divorced	13 (10)		4 (3)		5.15	.02
Ever Divorced	42 (31)		16 (12)		15.07	.001
Currently Incarceratedg	6/161 (4)		1/149 (<1)		FET	.12

FET = Fisher’s Exact Test.

^a1=Higher executives, 8=Unemployed.

^b1 is highest social class, 5 is lowest.

^cAmong employed subjects.

^dt-test for unequal variances.

^eMedian test.

^fRange 1–6: 1=Superior, 2,=Very Good, 3=Good, 4=Average, 5=Fair, 6=Poor.

^gOf those located at FU41 (161/207 probands, 149/178 controls).

Similarly, probands had significantly lower occupational attainment levels. On average, the comparison group had mid to high-level occupational attainment (mean, 3.0±1.8), whereas the index cases were at the low end (mean, 4.7±2.0). Given the probands’ worse educational and occupational attainment, their relatively poorer SES at FU41 is to be expected (p<.001). Although significantly fewer probands than comparisons were employed (p<.01), the great majority were holding jobs (84%). However, the disparity of $40,000 between the median annual salary of employed probands and comparisons is striking.

Occupational and Social Functioning

Employed probands, as a whole, had average to good work performance (mean, 3.2±1.1). However, comparisons were significantly superior (P<.001), with good to very good functioning (mean, 2.5±.9) (Table 1).

Similarly, probands’ mean overall social functioning was relatively worse, but not clinically impaired. Probands had average to good social functioning (3.8±1.3), whereas comparisons had good to very good social adjustment (2.9±1.0) (p<.001).

Marital Status

Although the majority in both groups were cohabiting with a spouse (70% and 79%) (Table 1), significantly more probands were currently divorced (10% vs. 3%, p<.05), and had ever been divorced (31% vs. 12%, p<.001).

Ongoing Psychiatric Disorders at FU41

ADHD

As hypothesized, at mean age 41, ADHD was significantly more prevalent in probands than comparisons (22% vs. 5%, p<.001) (Table 2). The three types of ADHD, Combined, Inattentive, and Hyperactive/Impulsive, were equally frequent in probands (7%, 7%, and 8%, respectively).

Table 2.

Rates of Ongoing DSM-IV Disorders at Follow-Up 41^a

DSM-IV Diagnosis	Probands (n = 135) n (%)	Comparisons (n = 136) n (%)	χ2	p ≤
ADHD	30 (22)	7 (5)	16.76	.001
Combined	9 (7)	1 (1)	FET	.01
Predominantly Inattentive	10 (7)	2 (1)	5.64	.02
Predominantly Hyperactive-Impulsive	11 (8)	4 (3)	3.51	.06
Antisocial Personality Disorder	22 (16)	0 (0)	FET	.001
Alcohol-Related Disorder	13 (10)	21 (15)	2.09	.20
Substance Disorderb	19 (14)	7 (5)	6.23	.01
Nicotine Dependence	41 (30)	12 (9)	19.99	.001
Any Mood Disorder	12 (9)	8 (6)	0.90	.36
Any Anxiety Disorder	17 (13)	12 (9)	1.01	.33

^aDefinite DSM-IV diagnoses

^bOther than alcohol-related disorder and nicotine dependence.

FET = Fisher’s Exact Test.

Antisocial Personality Disorder (ASPD)

As hypothesized, ongoing ASPD was elevated in probands; 22/135 probands (16%), but no comparison case, had ASPD at FU41 (p<.001) (Table 2).

Alcohol and Substance Disorders

Prevalence of alcohol-related disorders did not differentiate the groups (p=.20). In contrast, probands had a threefold greater rate of ongoing SD and nicotine dependence than comparisons (p’s = .01 and <.001) (Table 2).

Mood and Anxiety Disorders

Groups did not differ in frequency of ongoing mood (9% and 6%) or anxiety disorders (13% and 9%) for probands and comparisons (p’s=.36 and .33, respectively) (Table 2).

Comorbidity in Probands between Persistent ADHD, ASPD, and SD

Contrary to hypothesis, ongoing ADHD was not related to ASPD (p=.24), but it was to ongoing SD (p=.04) at FU41 (Table 3). Probands with ongoing ADHD were three times more likely to have a drug use disorder than probands without ADHD. The association between ADHD and concurrent diagnoses of both ASPD and SD was also significant, with a fourfold increase in ASPD+SD in probands with ongoing ADHD (p=.04). There was no significant elevation of alcohol-related disorders or nicotine dependence as a function of ongoing ADHD (Table 3).

Table 3.

Relationship between Ongoing ADHD, Antisocial Personality Disorder, and Substance Disorders among Probands at Follow-Up 41

DSM-IV Diagnosis	ADHD		χ2	phi	p
	YES (n = 30) n (%)	NO (n = 105) n (%)
Antisocial Personality Disorder	7 (23)	15 (14)	1.4	.10	.24
Alcohol-Related Disorder	4 (13)	9 (9)	FET	.07	.49
Substance Disordera	8 (27)	11 (10)	FET	.19	.04
Nicotine Dependence	13 (43)	28 (27)	3.07	.15	.08
Antisocial Personality Disorder AND Substance Disorder	4 (13)	3 (3)	FET	.20	.04

FET = Fisher’s Exact Test.

^aOther than alcohol-related disorder and nicotine dependence.

Lifetime Functioning

Incarcerations and Deaths

Relative to comparison cases, a significantly larger proportion of probands had been incarcerated (36% versus 12%; p≤.0001), and were deceased (7% versus 3%; p=.05)(Table 4).

Table 4.

Lifetime Rates of Incarcerations^a, Deaths, and Mental Disorders^b

Outcome	Probands n = 135 n (%)	Comparisons n = 136 n (%)	χ2	p ≤
Incarcerated	49 (36)	16 (12)	22.36	.0001
Deceased	15/207 (7)	5/178 (3)	3.83	.05
Conduct Disorderc	84 (62)	36 (26)	35.1	.0001
Antisocial Personality Disorderd	44 (33)	5 (4)	38.24	.0001
Alcohol- Related Disorder	61 (45)	56 (41)	0.44	.51
Substance Disordere	76 (56)	52 (38)	8.87	.003
Nicotine Dependence	81 (60)	42 (31)	23.17	.0001
Any Mood Disorderf	66 (49)	58 (43)	1.06	.30
Any Anxiety Disorder	25 (19)	28 (21)	0.18	.67

^aFor one day or more (not restricted to jail sentences).

^bProbable and Definite diagnoses

^cPrior to age 18.

^dDiagnosis requires previous history of conduct disorder.

^eOther than alcohol-related disorder and nicotine dependence.

^fMostly Major Depressive Disorder: 51/66 Probands (77%); 54/58 Comparisons (93%).

Rates of Lifetime Mental Disorders

Over their lifetime, probands had significantly elevated rates of ASPD, SD and nicotine dependence (p=.003-.000) (Table 4). Lifetime rates of SDs and nicotine dependence were not low among comparisons (38% and 31%, respectively), yet, probands significantly exceeded these frequencies (56% and 60%). Probands did not differ in lifetime alcohol-related disorders (p=.51), or lifetime mood and anxiety disorders (p’s=.30 and .67).

We note lifetime prevalence of bipolar disorder because of interest in its relationship to childhood ADHD.²³ Two probands (1.5%) had bipolar disorder; another was frankly psychotic.

Psychiatric Hospitalizations

33/135 probands (24.4%) had been hospitalized in a psychiatric facility, compared to 9/136 comparisons (6.6%; p<.001). Moreover, hospitalized probands had significantly more hospitalizations (mean, 3.36±4.26, range 1–24) than hospitalized comparisons (mean, 1.56±0.88, range 1–3; p=.03). In both groups, most hospitalizations were related to substance abuse (79% and 78%).

Onset of Mental Disorders in Adulthood (age 21 and beyond)

We posited that childhood ADHD would increase risk for psychiatric disorders throughout life (other than ADHD and ASPD, which require childhood onsets). This common expectation was not supported. Probands were not significantly more likely to incur new mental disorders in adulthood, but a trend was found for elevated mood disorders in probands (31% vs. 22%, χ²=2.85, p=.09).

Social and Occupational Functioning in Probands without an Ongoing Mental Disorder

At FU41, 44/135 probands (33%) did not meet criteria for any mental disorder. As predicted, these probands had significantly worse social functioning than comparisons (means, 3.55±1.25 and 2.89±0.97; t=3.19, p=.002). However, only a trend for worse occupational functioning was found (means, 2.98±1.2 and 2.62±1.1; t=1.84, p =.07).

Discussion

This prospective follow-up of children diagnosed with ADHD at mean age 8 years, selected to be free of conduct disorder, reaches into the fourth and fifth decades. Previous longitudinal studies have been limited to the second and third decades of life.

Compared to peers without ADHD, probands displayed dysfunction in multiple domains as adults. Educational and occupational attainment was significantly compromised, leading to relative economic disadvantage. Although the great majority of probands were employed (84%), and their median income was above that for white males in NY State (in 2007: $52,370)²⁴ they fared much more poorly economically than their non-ADHD peers. It is only relative to children without evidence of childhood ADHD that decrements in adult economic attainment become evident. The same pattern occurred with regard to occupational and social functioning. On average, probands had adequate adjustment, but it was inferior to comparisons’. Similarly, rates of currently and ever divorced of the index group were not especially high (10% and 31%, respectively), but they were threefold higher than comparisons’ (3% and 12%).

As anticipated, ongoing ADHD was relatively more prevalent in the group with childhood ADHD, but the rate in comparison cases was not nil (5%), similar to the 4% prevalence reported in a population whose childhood ADHD was retrospectively established.²⁵ We suspected that comparisons’ ADHD symptoms might have emerged during adulthood. However, all seven comparison cases with ongoing ADHD reported impairing ADHD symptoms before age 12, and all but one indicated an onset before age 7. Yet, only 1/7 comparisons with ADHD at FU41 had ADHD at FU18, based on parent- and self- report. Similarly, probands’ self-reports of ADHD at FU25 were much lower than at FU41 (4% vs. 22%). Increases in self-reported ADHD, over time, have also been reported by Barkley et al.⁸ Inconsistencies in adults’ retrospective reports of childhood ADHD raise questions about our ability to generate meaningful estimates of the disorder from adult recall.

Why is there an increase in self-reported ADHD in adults with childhood ADHD over time? We relied on DSM-IIIR criteria at FU25, and DSM-IV at FU41, whose standards for diagnosing ADHD differed. Higher rates of ADHD have been reported utilizing DSM-IV than DSM-III-R,²⁶ however, this feature does not seem explanatory, since ADHD at FU25 was only 7.4% in probands, if criteria include any significant inattention, hyperactivity or impulsivity symptom.^{9, 12} A possible factor may be greater awareness of ADHD due to wide media coverage, which has even promoted ADHD as reflecting special, positive, attributes.²⁷ Alas, advantages associated with ADHD have yet to be documented. It may be that the popularity of ADHD in the media has fostered erroneous self-identification leading to secular changes in self-identified ADHD, rather than true changes in prevalence. It is also possible that impairing inattention, hyperactivity and impulsivity develop in later life, when mental alacrity and resources decline, or accruing demands may exceed capacity (i.e., the Peter Principle). In such instances, adults may reinterpret their early history as a function of current difficulties. On the other hand, media promotion of ADHD may attune people to it, and foster accurate recognition and recall of dysfunction in childhood.

In childhood, all probands had combined ADHD. At follow-up, each type of ADHD was equally prevalent. However, assuming absence of inattention in probands with Predominantly Hyperactive/Impulsive ADHD conveys an erroneous clinical message, since all reported impairing inattention (median, 3 symptoms), but failed to meet the diagnostic threshold of 6/9 inattention symptoms. This finding concords with Barkley et al.’s view that, in adu ADHD types are not clinically meaningful in adults.⁸

It has been argued that standards for diagnosing ADHD should be lower in adults than children, requiring 4/9, instead of 6/9 clinical criteria.⁸ In this study, applying the 4/9 standard increases ADHD in probands by nearly half, from 22% to 32%, and more than doubles the rate in comparisons (from 5 to 12%), possibly leading to false positive diagnoses.

Although findings do not suggest a grim outcome for most children with ADHD, a substantial minority had very negative outcomes. Death and incarceration, arguably the worst possible lifetime events, were both significantly elevated in those with childhood ADHD. Almost a fifth had antisocial personality, a disorder that carries multiple serious consequences. Of probands who had probable or definite conduct disorder, at some point during adolescence (n=84/135), a quarter (n=22/84) had ASPD at FU41. In contrast, of comparison cases with an adolescent history of conduct disorder (36/136), none had ASPD at FU41 (Tables 2 and 4).

Only a proportion of children with conduct disorder have been shown to go on to ASPD in adulthood.²⁸ In this study also, most children with ADHD who developed conduct disorder during adolescence did not have ASPD at FU41. Thus, some dysfunctions of children with ADHD do attenuate during adulthood.

Childhood ADHD, without conduct disorder, elevated the risk for development and, importantly, maintenance, of antisocial disorders. As we previously reported, these, in turn, were associated with drug abuse and dependence, which had a profoundly negative impact through their associated criminality.²⁹ Elevated rates of substance use disorders cannot be attributed to differential rates of exposure to drugs of abuse during adolescence by probands and comparisons; the great majority in both groups (90 and 83%, respectively) had tried drugs, defined as using at least five times.³⁰

Consistent with other prospective studies,^{14, 31} findings do not support that ADHD per se places children at increased risk for mood and anxiety disorders, as suggested elsewhere.³² Lifetime rates of these disorders were not low in probands, but no higher than in comparisons. A study by Barkley is unique in reporting significantly more major depression in probands than comparisons at age 21,² but this difference disappeared at the next follow-up, 6 years later.⁸ No follow-up of children has found differential rates of bipolar and anxiety disorders in adulthood. In this study, two probands had definite bipolar disorder, and one late onset psychosis. Frequencies do not exceed population prevalences, and are too low for meaningful contrasts, but might suggest distinct psychopathogical processes in a minor subset of children with ADHD.

Our findings in a relatively severe clinical sample of ADHD children, free of conduct disorders, are consistent with several population studies^33–37 reporting that ADHD or ADHD symptoms do not predict SD when controlling for conduct disorder or problems. Rather, conduct problems mediate the predictive relationship between childhood ADHD and subsequent SD. At mean age 18, we found high comorbidity among persistent ADHD, ASPD, and SD.⁴ At mean age 25, ASPD and SD were no longer significantly associated with ongoing ADHD.^{9, 12} Thus, both ASPD and SD developed while ADHD persisted, but they continued even after ADHD remitted.^{9, 12} In contrast, at mean age 41, ongoing ADHD and SD were significantly, but not strongly, related (phi=.20 (Table 3). Interpretation of this association is not straightforward, since some drugs of abuse may have behavioral effects that mimic ADHD symptoms.

The study excluded children who have both ADHD and conduct disorder between ages 6 and 12. Therefore, results may not apply to such children. However, this diagnostic restriction was planned, and results inform on a well defined clinical group of ADHD children, independent of the confounding effect of co-occurring conduct disorder in childhood. Estimates of prevalence of conduct disorder in children with ADHD vary.³⁸ In the MTA study of children with ADHD, of both sexes and all racial groups, the rate of conduct disorder was 14.3%.³⁹ Therefore, study findings appear relevant to most children with ADHD. Nevertheless, the exclusion of conduct disorder may suggest that children in the present study had relatively mild forms of ADHD. Although this possibility cannot be ruled out, it does not seem probable since the mean teacher rated Hyperactivity Factor Score of this cohort was 2.11+0.46 (rated 0–3), somewhat higher than the MTA sample mean of 1.82±0.49 (no other longitudinal study reports teacher ratings).

We note several limitations. The design precludes generalizing to females, and all ethnic and social groups, since probands were Caucasian males, of average intelligence, referred to a clinic, with Combined Type ADHD. They do not inform on predominantly inattentive ADHD, especially if there is no history of impairing hyperactivity/impulsivity.

Comparisons lost to follow-up had lower IQ’s than those assessed; they also tended to have lower SES and more previous drug-related disorders, and information could not be obtained for the two with ASPD at FU25 (one was deceased). Therefore, contrasts between probands and comparisons may exaggerate somewhat the relative dysfunctions of adults who had ADHD in childhood. Also, study diagnoses reflect self-reports, and different results might emerge with input from significant others. Another limitation concerns missing subjects. Of 192 living probands 61 (31.8%) were lost to follow-up, Additionally, some contrasts had limited power, which may have precluded the detection of significant associations.

Comparisons had far superior median incomes than probands. However, comparisons do not appear to represent a super normal group. A sizable proportion had conduct disorder in adolescence (26%), and their incarceration rate (one day or more in jail) is not very low (12%). Further, a large proportion of comparisons qualified for a lifetime psychiatric diagnosis (combining subthreshold and full diagnoses) (Table 4), sometimes exceeding population rates.⁴⁰ It seems more compelling that differences at mean age 41 between probands and comparisons reflect differential development, especially since findings are highly consistent with other, briefer, follow-up studies.

In conclusion, the course of childhood ADHD shows a consistent clinical pattern from late adolescence well into adulthood. The longitudinal findings support the diagnostic validity of ADHD, as defined in this sample, since ADHD did not predict a medley of disorders in adulthood. At the same time, longitudinal findings point to clinical heterogeneity in childhood ADHD, since course was negative in only a subset.

Although the pattern of psychopathology from early to later adulthood in probands did not show striking changes, rates of dysfunction diminished. The trajectory of antisocial disorders in probands was consistent with reports of the disorders’ gradual remission over time.⁴¹ However, through life, those who had developed conduct disorder fared relatively badly, with a substantial minority having very negative life circumstances. The period of increased relative risk for new psychopathology was limited to adolescence. This should not be construed as meaning that probands were not worse off in adulthood than comparisons. They were; but relative disadvantages in adulthood reflect persistent malfunction with earlier origin. As such, findings stress the importance of continued monitoring and treatment of children with ADHD, even when conduct disorder is not evident.