Attention Deficit Hyperactivity Disorder (ADHD) Among Longer-term Prison Inmates is a Prevalent, Persistent and Disabling Disorder

Ylva Ginsberg; Tatja Hirvikoski; Nils Lindefors

Disclosures

BMC Psychiatry. 2010;10(1) 

In This Article

Results

ADHD Prevalence

Figure 1 presents a flowchart of the study. As calculated from this figure, the total response rate was 62% (194/315). We defined adult ADHD as reaching the cut-off levels for both childhood and adult ADHD. By this procedure, we increased the specificity of the screening survey. When applying our predefinition of adult ADHD, the prevalence rate was 45%, as 88 out of 194 subjects fulfilled this definition (Figure 1). Overall, responders were slightly older and served longer convictions compared with non-responders (Table 1). However, when we assessed 34 subjects marking ADHD by the screening, we confirmed ADHD among 30 of them. Thus, the screening survey pointed out to be 88% (30/34) specific. Therefore, we imply a more conservative 40% ADHD prevalence (0.88 × 45) among longer-term prison inmates.

Clinical Characteristics of ADHD among Adult Male Prison Inmates

This study included an extensive diagnostic evaluation of ADHD and coexisting disorders among a group of prison inmates (Figure 1). Table 2 shows the clinical characteristics of those 30 subjects confirmed with ADHD. As shown, almost all subjects confirmed ADHD of the combined type. Further, all subjects presented coexisting disorders. In fact, all 30 subjects presented a lifetime history of SUD, with amphetamine as the most preferred drug among almost two thirds. In general, the subjects showed an early onset of abuse and antisocial behaviour. In addition, lifetime mood and anxiety disorders were obvious among a vast majority and treated among almost half of subjects at the assessment. Besides, almost one fourth confirmed ASD, much more common than we expected. On the other hand, psychopathy was present among only one tenth, which was less than we expected. Further, personality disorders were present among 96% (22/23) of subjects. Among personality disorders, antisocial, borderline, paranoid, narcissistic, or obsessive-compulsive personality disorder were most obvious. Further, there was a striking finding of this study; despite most subjects reported prior need of health services and educational support at school, few received a diagnosis of ADHD during childhood. In summary, prison inmates showed severe symptoms and severities from ADHD, SUD, ASD, personality disorders, mood- and anxiety disorders.

Comparisons between ADHD Prison Inmates, ADHD Psychiatric Outpatients, and Healthy Controls

As depicted in Table 2, all three groups were of similar age. Notably, 83% of ADHD prison inmates fulfilled nine-year of compulsory school or less, compared with 30% among ADHD psychiatric outpatients, and 6% among healthy controls, thus reflecting a remarkably lower educational level among prison inmates.

Standardised Questionnaires

The ADHD-prison group rated more ADHD related symptoms and behaviours during both childhood and adulthood, compared with the ADHD-psychiatry group (Table 3). By contrast, when parents retrospectively rated childhood symptoms and behaviours, differences between groups were negligible, which we did not expect. Table 3 presents statistics and Figure 2 presents mean values (+/- 2 SE), respectively.

Figure 2.

Retrospective ratings of childhood symptoms by the Five to Fifteen questionnaire as completed by significant others, for the ADHD-psychiatry group (n = 15) and the ADHD-prison group (n = 14), respectively.

Neuropsychological Tests

The dyadic estimation of IQ displayed similar IQ for controls and the ADHD-psychiatry group; (Controls, n = 18, M = 112 (± 9.65), range 97 - 132); (ADHD-psychiatry, n = 20, M = 108.25 (±11.48), range 89 - 132). On the other hand, IQ was substantially lower among ADHD prison inmates; (M = 95.18 (± 9.99), range 78 - 113). The ADHD-prison group (n = 22) had missing data for eight subjects. We expected significant differences between groups on estimated IQ (F = 14.76, p < .001, η p 2 = .341) because of different inclusion criteria. In fact, only the ADHD-prison group included subjects with IQ between 70 and 85. As a result, 10% (3/30) of prison inmates presented estimated dyadic IQ within this range, specifically between 78 and 85. Therefore, we excluded those three inmates with IQ < 85 for making inclusion criteria homogenous. However, the ADHD-prison group still showed lower estimated IQ after performing this procedure, compared with both other groups (F = 10.49, p < .001, η p 2 = .28).

Neuropsychological Tests of Executive Functions

The ADHD-prison group showed poorer results on several measures of executive functions compared with both other groups, also when controlling for IQ (Table 4).

On measures of working memory, controls outperformed the ADHD-psychiatry group on both verbal (DS) and visuo-spatial working memory (SB). On the other hand, the ADHD-psychiatry group outperformed the ADHD-prison group on the same measures. However, when controlling for IQ, the differences in working memory between ADHD groups no longer remained, but controls still outperformed both ADHD groups. Thus, both working memory tests showed executive dysfunctions associated with ADHD, also when controlling for IQ.

On the Conners' Continuous Performance Test II (CCPT), controls and the ADHD-psychiatry group showed similar results. However, at least one of the other groups outperformed the ADHD-prison group on all four accuracy dependent measures, and in three out of seven variability dependent measures, respectively. On the other hand, there were no significant differences in reaction time between groups (Table 4 and Figure 3). Notably, 5 out of 27 (18.5%) subjects among the ADHD-prison group showed remarkably increased values (T-score >200) on Perseverations, a measure considered to reflect flexibility. Therefore, we performed analyses both including and excluding subjects with extreme values. However, we observed similar results on Perseverations also when excluding those subjects, thus implying decreased flexibility among prison inmates with ADHD. Further, estimated IQ did not explain the CCPT results in this study (Table 4).

Figure 3.

The Conners' Continuous Performance Test II (CCPT). Results are presented for controls (n = 18), the ADHD-psychiatry group (n = 20), and the ADHD-prison group (n = 27), respectively. The CCPT results did not co-vary with IQ. Note: * the ADHD-prison group performed significantly poorer than at least one of the other groups (ADHD-psychiatry and controls).

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