ADHD Undetected in Criminal Adults

Abstract

Objective: The objective of this study was to assess whether adults with ADHD in a forensic sample had received the diagnosis earlier and to investigate reasons for missing the diagnosis earlier. Method: From December 1, 2007 until March 5, 2009, all patients from an outpatient clinic for forensic mental health care who were suspected of having ADHD were seen by a psychiatrist who assessed presence and severity of ADHD symptoms and other psychiatric disorders in a standardized way. Results: ADHD diagnosis was missed previously in life in 59 of 106 male adults (56%). ADHD diagnosis was missed more often in older men, in those with hyperactive/impulsive or combined subtype of ADHD, in those who reported fewer symptoms of ADHD in childhood or adolescence, in those with a comorbid mood disorder in adulthood, and in those who had never received mental health care before. Even in those who had previously received mental health care, the diagnosis had been missed in 42% of the cases. Prior contacts with police or court also predicted missing the diagnosis, an effect that was mediated by a lower chance to be referred to mental health care. Conclusion: General and forensic mental health care workers should be alert for the fact that ADHD is missed very often in individuals who have problems with delinquency and should realize that ADHD may be masked by various factors.

Keywords

ADHD delinquency underdiagnosis underdetection screening

Detection of ADHD in Criminal Adults

ADHD is one of the most common childhood disorders. Its population prevalence is 5% in children, and 3% to 4% in adolescents and adults (Faraone, Sergeant, Gillberg, & Biederman, 2003; Fayyad et al., 2007; Kessler et al., 2005; Polanczyk & Rohde, 2007).

ADHD is often accompanied by life lasting dysfunctioning in multiple areas. Adults with ADHD tend to be lower educated, have problems with occupational functioning and problems with relationships, are at higher risk for car accidents, often have substance use disorder, tend to be more aggressive, and are frequently involved in criminal activities (Barkley, Fischer, Edelbrock, & Smallish, 1991; Biederman et al., 1993; Mannuzza & Klein, 2000; Wilens & Spencer, 2010). Several studies have shown that impulsivity/hyperactivity in childhood specifically predicts future delinquency because of its association with conduct disorder (CD; Babinski, Hartsough, & Lambert, 1999; Pardini, Obradovic, & Loeber, 2006). Studies that compared ADHD patients with controls found a higher prevalence of delinquency in those with ADHD (Blanz, Schmidt, & Esser, 1991; Mannuzza, Klein, Bessler, Malloy, & LaPadula, 1998; Weiss, Hechtman, Milroy, & Perlman, 1985). Fang, Massetti, Ouyang, Grosse, and Mercy (2010) found an association between childhood ADHD and future intimate partner violence.

In society and in media, ADHD being diagnosed too often is a trending topic. In a recent review, Garfield et al. (2012) concluded that “in 10 years, the ambulatory diagnosis of ADHD increased by two-thirds and is increasingly managed by psychiatrists” (p. 1). Critics talk about ADHD being a hype and claim that children receive the diagnosis of ADHD too quickly (DosReis, Barksdale, Sherman, Maloney, & Charach, 2010; Jensen et al., 1999). It was recently shown that clinicians do not always adhere strictly to diagnostic manuals, which may result in false positive diagnosis of ADHD (Bruchmuller, Margraf, & Schneider, 2012), although empirical evidence of systematic overdiagnosis of ADHD in large numbers of patients is lacking. Moreover, some clinicians and scientists claim the opposite: ADHD might remain unrecognized frequently, especially in women and adults (Sciutto & Eisenberg, 2007). In fact, both may be true: ADHD may remain undetected in some children, whereas other children may wrongly receive a diagnosis of ADHD.

Delinquency is one of the poorest thinkable outcomes of ADHD. There are some studies about prevalence of ADHD in individuals who display delinquent behaviors. Prevalence rates vary from 9% to 45% (Appelbaum, 2008). A Dutch study (Bulten, Nijman, & van der Staak, 2009) among 191 male prisoners found a lifetime prevalence of 38%. A recent study among male prisoners in Sweden found a lifetime prevalence of ADHD of 40% (Ginsberg, Hirvikoski, & Lindefors, 2010). One of the conclusions of a consensus statement of the U.K. adult ADHD and criminal justice agencies is that prevalence of adult ADHD is very high in prisons and the risk of aggressive incidents is high in inmates with ADHD (Young et al., 2011). Prevalence rates of ADHD in outpatient forensic mental health care are not known but can be expected to be high, given high prevalence rates in prisoners. Still, it has never been studied whether the issue of underdiagnosing ADHD also counts for individuals with a delinquent outcome. If so, more efforts regarding earlier recognition and detection of ADHD might be important to prevent delinquency.

There are several hypotheses about underdiagnosis or late diagnosis of ADHD. One hypothesis is about the presence of symptoms in childhood. If childhood ADHD symptoms are less present, this might lower the tendency to seek help. Another hypothesis is that the inattentive subtype of ADHD, not characterized by overt behavioral symptoms being a burden to others, is poorly recognized.

Other hypotheses pertain to the history of ADHD in society in the past decades. First, the fact that ADHD may persist into adolescence and adulthood has only recently—the past 15 years—been acknowledged. In the Netherlands, the first publications about ADHD persisting into adulthood were published in 1996 (Herpers & Buitelaar, 1996; J. J. Kooij, Goekoop, & Gunning, 1996). Second, before 1980, when the Diagnostic and Statistical Manual of Mental Disorders (3rd ed.; DSM-III; American Psychiatric Association [APA], 1980) described ADHD for the first time, it was impossible to assign the diagnosis. So, it is likely that older individuals with ADHD will have remained undetected during their childhood. Third, ADHD is far more prevalent in boys than in girls (Akinbami, Liu, Pastor, & Reuben, 2011). It is often presumed that girls with ADHD tend not to be detected because they more often suffer from the inattentive type. Furthermore, girls with ADHD tend to suffer from different comorbid disorders, compared with boys. Comorbid anxiety and depression in girls may attract less attention than comorbid behavior problems in boys, which are likely to be a reason for referral to mental health services, and therefore enhance detection (Biederman et al., 1999; Biederman et al., 1993).

Furthermore, it is possible that, independently from a gender difference in comorbidity patterns, comorbid behavioral or psychiatric problems, as well as severe dysfunctioning, have hindered the detection of ADHD, by masking the symptoms, or on the contrary, have promoted detection of ADHD, because help was sought earlier.

Finally, getting in contact with the police or court earlier in life might have promoted recognition of problems, referral to mental health services, and therefore, detection of ADHD.

The first aim of this study was to assess whether adults with ADHD in a forensic sample had received the diagnosis earlier. The second aim was to investigate why some individuals, who suffer from ADHD, have not received the diagnosis earlier in life, despite its presence. It was investigated if not having received a correct ADHD diagnosis was predicted by age, previous mental health care, previous contact with police or court, inattentive subtype of ADHD, presence of the symptoms in childhood and adolescence, dysfunctioning due to ADHD in childhood or adolescence, current psychiatric comorbidity, and global functioning.

Method

Procedure

All participants were recruited at “De Waag.” De Waag is a multicenter forensic outpatient clinic in the Netherlands (Amsterdam, Rotterdam, The Hague, Leiden, Haarlem, Utrecht, Amersfoort, Almere). At De Waag, patients with delinquency and mental problems are treated. Patients are referred by court, probation service, or primary health care.

At De Waag, all patients who are suspected for a psychiatric disorder or who report having a psychiatric disorder at intake are referred to a psychiatrist by the professional (psychologist, psychiatric nurse, social worker) who conducts the first assessment. If, subsequently, during the study, a psychiatrist suspected ADHD, he or she assessed ADHD symptoms via a standardized interview checklist containing all DSM-IV (APA, 1994) criteria for ADHD, and he or she assessed the presence of symptoms and the severity of dysfunctioning during childhood, adolescence, and adulthood in a standardized way. Furthermore, unstandardized routine psychiatric assessment yielded information regarding comorbid disorders (including substance use disorders). Data regarding all patients aged 18 or above who received a diagnosis of ADHD after psychiatric assessment, from December 1, 2007, until March 5, 2009, at one of the sites, were used for the present study.

Information regarding ADHD was obtained from patients themselves (100%), at least one of the parents (33 individuals, 30%), a grandmother (1 individual, 1%), and partner (8 individuals, 7%). Furthermore, all available patient record information was used.

Participants

The sample consisted of 109 patients: 106 men and 3 women. Because of the low number of women, it would be impossible to generalize the results to all women. Therefore, we removed the women from the sample, and only used data of the 106 men. This made it impossible to investigate whether gender predicted missing diagnosis of ADHD earlier in life.

Instruments

ADHD diagnosis was established via a standardized semistructured interview tapping all DSM-IV ADHD symptoms. This standardized interview was based on the approach that is followed by existing validated interviews for adolescents and adults such as the structured diagnostic interview for ADHD in adults 2.0 (DIVA 2.0; J. J. S. Kooij, 2012) or the Schedule for Affective Disorders and Schizophrenia for School-Age Children (K-SADS; Puig-Antich & Chamber, 1978), in which ADHD criteria are checked by assessing the presence or absence of each symptom by mentioning examples of behaviors fitting to a symptom. The difference between the approach that was used and the DIVA 2.0 or K-SADS is that, in our study, the interviewer was allowed to mention examples of behaviors fitting to each ADHD symptom, based on his or her clinical experience, whereas in the DIVA 2.0 or K-SADS, examples of behaviors are listed for each symptom in the text of the interview. All psychiatrists who participated in this study were experienced in diagnosing ADHD. Each criterion was scored based on information from the patient and, if possible, on information from a partner or from one or both parents. If medication for ADHD was used during the assessment (n = 24, 23%), it was assessed for each ADHD item whether it was present during the interview and whether it had been present before the start of medication.

The psychiatrists scored the presence of current ADHD symptoms (inattention symptoms and hyperactivity/impulsivity symptoms) and the presence of ADHD symptoms in the past, during childhood (6-11 years) and adolescence (12-17 years), on a 3-point scale: 0 = not/merely present, 1 = moderate presence, and 2 = strong presence.

The severity of dysfunctioning due to ADHD symptoms in three life periods was scored by counting the areas in which the individuals dysfunctioned in each of these periods. It was asked,

In which of the following areas, problems with dysfunctioning because of ADHD were present during childhood (6-11 years): (a) severe problems with parents, (b) severe behavioral problems at school, (c) severe learning problems, and (d) severe problems with other children? A total score was derived (range = 0-4), which indicated the number of areas in which problems were present during childhood (range = 0-4).

In which of the following areas, problems with dysfunctioning because of ADHD were present during adolescence (12-17 years): (a) severe problems with parents, (b) severe behavioral problems at school or at work, (c) severe learning problems, and (d) severe problems with other adolescents? A total score was derived (range = 0-4), which indicated the number of areas in which problems were present during adolescence.

In which of the following areas, problems with dysfunctioning because of ADHD were present during adulthood (18 years and older): (a) severe problems with parents, (b) severe behavioral problems at school or at work, (c) severe learning problems, (d) severe problems with partner relationships, (e) severe problems with other people, and (f) dysfunctioning in own family? A total score was derived (range = 0-6), which indicated the number of areas in which problems were present during adulthood.

Patients were asked whether they had received previous mental health care (yes = 0, no = 1).

Patients were asked whether they were diagnosed with ADHD before (yes = 0, no = 1).

Current DSM-IV Axis I and Axis II diagnoses other than ADHD and global assessment of functioning (GAF) score on referral to De Waag were based on routine psychiatric assessment.

Type of current delinquency was rated by the psychiatrist as present or absent, using the following categories: sex offense, domestic violence, physical assault, property offense, and other, such as fire setting. This rating was based on all patient record information, including results of the “Risicotaxatie-instrument voor de Ambulante Forensische GGZ” [RAF GGZ] a risk assessment instrument for outpatient forensic mental health service (Horn, Wilpert, Eisenberg, Scholing, & Mulder, 2012) that was administered to all patients. Presence or absence of previous lifetime police or judicial contacts, prior to the offense that had lead to referral to De Waag, was recorded by the first author (N.J.L.B) as present or absent, based on the same patient records.

Results

The first aim of this study was to assess whether adults with ADHD in a forensic sample had received the diagnosis earlier. A total of 47 individuals (44%) had already been diagnosed with ADHD before referral to De Waag. In all, 59 individuals (56%) received the diagnosis for the first time at De Waag.

The second aim of this study was to investigate factors that predict “a missed diagnosis of ADHD in childhood or adolescence.” For this reason, the following variables were investigated: age; previous mental health care; subtype ADHD, the inattentive type versus the other types; presence of ADHD symptoms during childhood (6-11 years) and adolescence (12-17 years); severity of dysfunctioning because of ADHD symptoms during childhood (6-11 years), adolescence (12-17 years), and adulthood (18 years or above); previous contact with police or court; psychiatric comorbidity (current DSM-IV Axis I and Axis II diagnoses other than ADHD); and GAF score (on referral to De Waag).

Mean age of the men was 29.4 years (M = 28, SD = 9.1, range = 18-51). A total of 13 (12%) were classified as sex offender, 34 (32%) had committed domestic violence, 77 (73%) had committed physical assault, 23 (22%) had committed property offense, and 9 (9%) had committed other types of delinquency. In all, 73 individuals (69%) were classified into one offense category and 32 (30%) into two or more offense categories.

A total of 57 individuals (54%) were also diagnosed by the psychiatrist with substance use disorder, 15 (14%) with mood disorder (depressive disorder or bipolar disorder), 7 (7%) with anxiety disorder (post traumatic stress disorder; PSTD; generalized anxiety disorder, panic disorder), 6 (6%) with sexual disorder (paraphilia or pedophilia), and 1 (1%) with pervasive developmental disorder.

A total of 29 individuals (27%) had a personality disorder: 14 (13%) antisocial personality disorder, and 15 (14%) some other personality disorder. Mean GAF score was 39 (M = 40, SD = 13.7, range = 15-70).

A total of 75 individuals (71%) showed previous delinquent behavior, which gave reason to contact with police or justice prior to being referred to De Waag.

A total of 81 individuals (76%) received mental health care prior to being referred to De Waag.

A total of 17 individuals (16%) had the inattentive subtype (A), 11 (10%) the hyperactive/impulsive subtype (HI), and 78 (74%) the combined subtype (C). In all, 74 individuals (70%) reported strong presence of attention problems and 78 (74%) strong presence of hyperactive/impulsive problems during childhood. A total of 83 (78%) reported strong presence of attention symptoms, and 81 (76%) reported strong presence of hyperactive/impulsive symptoms in adolescence (12-17 years).

A total of 22 individuals (21%) had severe problems in all four areas of functioning in childhood (median = 2 areas), 29 (28%) had severe problems in all four areas in adolescence (median = 3 areas), 6 (6%) had severe problems in all six areas in adulthood (18 years and older; median = 3 areas), and 49 (46%) had severe problems in four or more areas in adulthood.

A backward stepwise logistic regression analysis was carried out to investigate which of the variables described above predicted a missed diagnosis of ADHD prior to referral to De Waag. Criterion for inclusion was p < .10 and for exclusion was p > .05. Likelihood ratio tests were carried out to test the level of significance of each step. Using the possibility to compute a dummy variable, the variable “personality disorder” was recoded into 0 = reference category (no personality disorder), 1 = antisocial personality disorder, and 2 = other personality disorder.

The classification table of the regression analysis can be found in Table 1. The significance of the final model was p < .000 (chi-square = 58.16, df = 7, −2 log likelihood = 87.43, Nagelkerke R² = .56). Table 1 shows that in 78.7% of the cases, “ADHD diagnosis was missed” was predicted successfully, and in 79.7% of the cases, “ADHD diagnosis was not missed” was predicted successfully. Overall, 79.2% of the cases were classified correctly by the final model.

Table 1.

Classification Table Backward Stepwise Logistic Regression Analysis.

N = 106 men	Predicted: diagnosis of ADHD not missed	Predicted: diagnosis of ADHD missed	Percentage correct predicted
Diagnosis of ADHD not missed	37	10	78.7
Diagnosis of ADHD missed	12	47	79.7
	49	57	79.2

In Table 2, it is shown which predictors contributed significantly to the final model. The results indicate that the diagnosis of ADHD had more often not been assigned previously to older individuals (odds ratio [OR] = 1.08). The OR of 1.08 means that, with every increment of age with 1 year, the probability of a missed diagnosis was increased with a factor of 1.08. This means that, for example, the probability of missing the diagnosis in a 45-year-old man was 6.85 times higher than in a 20-year old man. The inattentive subtype was missed less often than the hyperactive/impulsive subtype and the combined subtype. The OR of 15.69 means that the chance of not having received the diagnosis on assessment at De Waag was 15.69 times higher for individuals with the hyperactive/impulsive or combined subtype, compared with the inattentive subtype. Fewer attention symptoms during childhood (OR = .32), fewer hyperactive/impulsive symptoms during childhood (OR = 0.94), and fewer hyperactive/impulsive symptoms during adolescence (OR = 0.14) predicted a previously missed diagnosis of ADHD. Previous mental health care was a strong predictor (OR = 12.52) of correctly having received the diagnosis of ADHD previously. In case of a comorbid mood disorder, it was more likely that the diagnosis of ADHD had been missed previously (OR = 4.93).

Table 2.

Results of First Backward Stepwise Regression Analysis (Outcome Variable = Missed ADHD Diagnosis).

Variable	Odds ratio
Age	1.08
Subtype ADHD (1 = ADD, 2 = other)	15.69
Presence of attention symptoms in childhood	0.32
Presence of attention symptoms in adolescence	ns
Presence of hyperactive/impulsive symptoms in childhood	0.94
Presence of hyperactive/impulsive symptoms in adolescence	0.14
Severity of dysfunctioning in childhood	ns
Severity of dysfunctioning in adolescence	ns
Severity of dysfunctioning in adulthood	ns
Previous police or court contact (0 = yes, 1 = no)	ns
Previous mental health care (0 = yes, 1 = no)	12.52
Comorbid substance use disorder (0 = no, 1 = yes)	ns
Comorbid mood disorder (0 = no, 1 = yes)	4.93
Comorbid anxiety disorder (0 = no, 1 = yes)	ns
Comorbid antisocial personality disorder (0 = no, 1 = yes)	ns
Comorbid other personality disorder (0 = no, 1 = yes)	ns
Global assessment of functioning	ns

Note: ADD = attention deficit disorder; ns = not significant.

The predictive power of the model we found was very high (almost 80% classified correctly). Because of the OR of 15.69 for previous mental health care as predictor, it could be argued that the strong predictive power largely depended on this sole variable. To this end, a new regression analysis, following a similar method as the one described above, was conducted, with a similar set of predictors, except for “previous mental health care,” which was removed from the set of candidate predictors. The resulting model (p < .000, chi-square = 49.94, df = 10, Nagelkerke R² = .503, −2 log likelihood = 95.65) classified 77.4% of the individuals correctly. The results of the second regression analysis are shown in Table 3. Instead of previous mental health care, missed diagnosis of ADHD was predicted now by severity of dysfunctioning in childhood (OR = 0.61), severity of dysfunctioning in adolescence (OR = 1.70), previous contact with police or court (OR = 0.31), and comorbid anxiety disorder (OR = 11.21).

Table 3.

Results of Second Backward Stepwise Regression Analysis (Without Previous Mental Health Care As Predictor).

Variable	Odds ratio
Age	1.10
Subtype ADHD (1 = ADD, 2 = other)	28.71
Presence of attention symptoms in childhood	0.38
Presence of attention symptoms in adolescence	ns
Presence of hyperactive/impulsive symptoms in childhood	0.10
Presence of hyperactive/impulsive symptoms in adolescence	0.08
Severity of dysfunctioning in childhood	0.61
Severity of dysfunctioning in adolescence	1.70
Severity of dysfunctioning in adulthood	ns
Previous police or court contact (0 = yes, 1 = no)	0.31
Comorbid substance use disorder (0 = no, 1 = yes)	ns
Comorbid mood disorder (0 = no, 1 = yes)	3.95
Comorbid anxiety disorder (0 = no, 1 = yes)	11.21
Comorbid antisocial personality disorder (0 = no, 1 = yes)	ns
Comorbid other personality disorder (0 = no, 1 = yes)	ns
Global assessment of functioning	ns

Note: ADD = attention deficit disorder; ns = not significant.

Discussion

The first aim of this study was to assess whether adults with ADHD in a forensic sample had received the diagnosis earlier. It appeared that the majority of the patients (56%) had never been diagnosed with ADHD before. The sample of the present study consisted of men with a poor outcome. All the men were referred because of delinquency, malfunctioned severely (M GAF score = 39), suffered from high rates of comorbid psychiatric disorders, and exhibited a pattern of dysfunctioning in multiple areas throughout their whole life, the median number of problem areas being two in childhood, three in adolescence, and three in adulthood. It can be presumed that, considering the availability of effective interventions for ADHD for children and adolescents, a part of these problems could have been prevented. The fact that, in a sample of patients with extremely high severity levels of problems, the diagnosis of ADHD had been missed so frequently underscores the urge for earlier detection and recognition of such patients.

The second aim was to investigate why some individuals who suffer from ADHD have not received the diagnosis earlier in life, despite its presence. Searching for opportunities for enhancing earlier detection, we investigated factors that predict in which patients the diagnosis of ADHD had been missed before. The analyses showed that ADHD diagnosis had been missed more often in older men, in patients with a hyperactive/impulsive or combined subtype of ADHD, in patients who had displayed relatively few symptoms of ADHD in childhood or adolescence, in patients who had never before referred to mental health services, and in those with a comorbid mood disorder in adulthood.

The predictive value of the set of significant predictors was very high. A total of 79% (first analysis with previous mental health care as predictor) of the patients were classified correctly. Furthermore, the strong relation between the predictor variables and the outcome was illustrated by the Nagelkerke R² of .56.

A diagnosis of ADHD had been missed more often in older patients. This could be explained by unfamiliarity of professionals with ADHD in the past. ADHD was described first in DSM-III in 1980 (APA, 2000). Post hoc, we calculated that 25% of the patients in whom the diagnosis of ADHD had been missed in the past were below 9 years of age in 1980. Furthermore, 25% of the patients in whom the diagnosis had been missed were 19 years or older in 1980. So it seems rational that in these individuals, ADHD has remained undetected in childhood and adolescence, the first group being a child while ADHD did not even exist and the second group being adult already, in a period in which it was believed that ADHD could occur in children and adolescents but not in adults. Still, it can also be concluded that, although the possibility to diagnose ADHD in adults has been acknowledged in the past 15 years, it was not detected, despite high levels of malfunctioning.

Our expectation was that ADHD diagnosis would be missed more often in individuals with the inattentive subtype. We found the opposite: The hyperactive/impulsive subtype was missed more often. A possible explanation for this finding is that, in this sample of delinquent individuals, hyperactive and impulsive symptoms were overlooked due to comorbid behavior problems.

Fewer attention and fewer hyperactive/impulsive symptoms in childhood, and fewer hyperactivity symptoms in childhood and adolescence predicted a missed diagnosis. This confirmed our hypothesis. Strong presence of symptoms promoted detection of ADHD. Moderate presence of symptoms hampered detection.

Patients who had previously received mental health care had a bigger chance of having received the diagnosis ADHD earlier in life. At first glance, it seems reassuring that those who had received mental health care were more likely to have received the right diagnosis. However, 81 individuals (76% of the sample) had received mental health care prior to admission to De Waag, whereas only 47 individuals (44% of the sample) had been diagnosed with ADHD previously. In other words, 34 individuals (32% of the sample, 42% of those who previously had received mental health care) had not received a diagnosis of ADHD, despite treatment at mental health services. This underscores the need for systematic assessment of ADHD in general mental health care.

A comorbid mood disorder during assessment at De Waag predicted a missed ADHD diagnosis. Although current, and not lifetime, depressive disorder was a variable in this study, it can be hypothesized that ADHD symptoms were masked by comorbid depressive symptoms, which may have hampered detection.

Post hoc, the predictive power of the statistical model was tested after omission of “previous mental health care” from the predictor set. The model remained highly predictive. A total of 77% of the individuals were classified correctly, and Nagelkerke R² was .50. Apparently, in addition to previous mental health care, other significant predictors contributed considerably to the predictive value of the model.

The post hoc analysis yielded revealed the following significant predictors that became significant instead of previous mental health care: severity of dysfunctioning in childhood (OR = 0.61), severity of dysfunctioning in adolescence (OR = 1.70), comorbid anxiety disorder (OR = 11.21), and previous contact with police or court (OR = 0.31). The results indicate that effects of these predictors may be mediated by referral to mental health services. In other words, these predictors may exert their influence via referral to mental health care.

This study has implications concerning forensic mental health care, general mental health care, and police and court. For those who work in forensic mental health care, it is important to notice that ADHD diagnosis is missed very often in the history of patients who are referred to forensic mental health care. The fact that the diagnosis was missed in more than half of the study sample is shocking and underscores the need for high alertness. To help identifying patients at risk, the results of the present study may be helpful. ADHD may easily be missed in older men and in individuals with hyperactive/impulsive problems. Furthermore, comorbid mood disorder may mask ADHD. In addition, those who never have been referred to mental health services are a potential risk group. Finally, the second regression analysis showed that contact with police or court previously in life is a risk factor for a missed diagnosis of ADHD. Hence, prior police or judicial contacts should alert forensic mental health care workers to consider the presence of ADHD. There are several screening instruments for adult ADHD, for example, the ADHD Rating Scale (Dupaul, Power, Anastopoulos, & Reid, 1998) and the Adult Self Report Scale (ASRS; Kessler et al., 2005). However, these self-report instruments have not been validated yet in a forensic population, so the value of using screening instruments is questionable. Because the estimated prevalence of ADHD in forensic psychiatry is high, and because the present study pointed out that the diagnosis is being missed very often, we recommend to evaluate the presence of ADHD in all individuals who are referred to forensic mental health services. If ADHD appears to be present, we recommend combined treatment of ADHD symptoms and delinquency. For ADHD, psychoeducation, medication, and cognitive behavioral therapy are the interventions of first choice, whereas to prevent delinquency, aggression regulation programs and social skills training, as well as family interventions—depending on the type of problem—can be recommended.

For those who work in general mental health care, the results implicate that systematic assessment of ADHD in children and in adults is needed. The diagnosis of ADHD is missed often, even in highly vulnerable individuals. Moderate presence of ADHD predicted missing the diagnosis. This may mean that, in those who do not display very high levels of symptoms, the severity of problems may be underestimated. Bearing in mind that all individuals in the present study’s sample were at high risk for delinquency, the results may indicate that, in delinquent patients, delinquency may mask ADHD, and may lead to too much emphasis on behavior problems, and underestimation of ADHD. Being stigmatized as a delinquent individual may lead professionals to consider the possibility of ADHD less often. There is no need to say that such a phenomenon represents missed chances to bend the development of individuals with ADHD toward a better direction, away from delinquency, thereby causing a higher burden not only to these individuals but also to their environment, later on. Screening instruments for ADHD can be used for detection in general mental health care, followed by thorough clinical assessment. Useful screeners for children are, for example, the Conners’ Rating Scales revised (Conners, 2001) or the Strengths and Difficulties Questionnaire (SDQ; Goodman, 1997). For adults, screeners mentioned earlier can be used, followed by a semistructured interview such as the DIVA 2.0.

Police or judicial contacts became a risk factor for missing the diagnosis of ADHD when referral to mental health care was removed from the analysis. This argues for regular screening for ADHD in those who have such contacts. This is in line with the findings of a recent study (Cohn, van Domburgh, Vermeiren, Geluk, & Doreleijers, 2012) in which rates of 34%, 12%, 8%, and 14% were found, respectively, for any externalizing disorder, ADHD only, oppositional disorder or CD only, and ADHD plus oppositional defiant disorder (ODD)/CD in a sample of 192 first-time arrestees aged 12 of younger. Based on these high prevalence rates, and the finding that the presence of one of these diagnoses predicted reoffending, the authors strongly recommend screening for mental health problems as well as interventions for first-time arrestees.

This study has yielded valuable results, the most remarkable result being a missed diagnosis of ADHD in more than half of the sample. However, the study has several limitations. These limitations may have influenced the results pertaining to prediction of missing the diagnosis to a considerable degree, but their influence on the primary result, the diagnosis of ADHD being missed very often, has probably been small. The study was carried out 3 years ago. As awareness of ADHD is developing it can be presumed that repetition of the study will show less missed ADHD diagnosis. Another limitation is constituted by the sample that was studied. The sample consisted of individuals with ADHD and delinquency who were referred for treatment, so it is risky to generalize the results to other populations. Also, selection of the ADHD patients depended on referral to a psychiatrist of De Waag by the professional who conducted the first assessment. Another limitation is constituted by the retrospective nature of the study. Finally we did not use validated structured interviews for assessing psychopathology. This can be seen as a limitation. However, ADHD symptoms were assessed carefully in a standardized way using information from different sources, which resembled the approach followed by validated interviews such as the DIVA 2.0. It can be questioned how this has influenced the results of the present study. By mentioning more signs fitting to each ADHD symptom, it can be expected that more cases with ADHD are detected, because the likelihood that a symptom is missed is being reduced. Hence, because not all the examples of ADHD behaviors that are comprised by standardized interviews such as the DIVA 2.0 were literally mentioned to the patient by the investigating psychiatrist, it can be argued that some patients with a relatively mild type of ADHD, having relatively weak symptoms, were not detected. Possible underdetection of ADHD during the sample selection for the present study does not change the main finding of the study, being that a diagnosis of ADHD is missed very often. Still, the findings of our study compel to carry out further investigation aimed at the prevalence of ADHD and comorbid disorders in forensic mental health care, using standardized instruments like DIVA 2.0, Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I; First, Spitzer, Gibbon, Williams, & Benjamin, 1997), and Structured Clinical Interview for DSM-IV Axis II diagnosis (SCID-II; First et al., 1997).

Conclusion

The diagnosis of ADHD is missed very often, even in a very high risk sample of delinquent individuals. General and forensic mental health care workers should be alert for this and should realize that ADHD may be masked by various factors.

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.

Author Biographies

Nannet J. L. Buitelaar, MD, is forensic psychiatrist at De Waag, De Forensische Zorgspecialisten, Utrecht, The Netherlands. Her main research interest is in ADHD and its influence on delinquency, personality disorders and domestic violence.

Robert F. Ferdinand, MD, PhD, is child and adolescent psychiatrist and director of the department of child and adolescent psychiatry at GGZ Delfland, Delft, The Netherlands. His main research interest is in anxiety, behavior disorders, taxonomy, psychophysiology, and informant differences.

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