Methods
Participants
Adult patients participated in the study from both high- and medium-security establishments in the Greater London area. Three hundred and forty-one mentally disordered offenders, all of whom were detained under the UK Mental Health Act 2007,135 were resident at these two secure services [241 (71%) at the high-secure service and 100 (29%) at the medium-secure service]. The majority of patients in these settings have a primary diagnosis of either serious mental illness (SMI; e.g. schizophrenia, schizoaffective disorder, bipolar disorder) or PD. Exclusion criteria included age > 65 years and those patients who were too mentally unstable to participate, had severe cognitive deficits due to neurological illness or head injury, posed a risk of violence to the researcher and/or who lacked capacity to consent to participate in the study. Of the 341 patients, 93 (27.3%) were identified as ineligible to participate; 68 (20%) did not meet study criteria and a further 25 (7%) were on trial leave or discharged prior to the assessment. Of the 68 patients who did not meet exclusion criteria, 28 lacked capacity to consent and 40 were mentally unstable. Thus, a total of 248 patients were eligible to take part in the study. From this sample of 248 patients, a further 115 (46%) patients refused to participate in the research. Hence, 133 participated in the study [92 (69.2%) from the high-secure psychiatric service and 41 (30.8%) from the regional medium-secure service].
Assessment procedure
The study took place over a 16-month period. An information sheet describing the study and specifying inclusion and exclusion criteria was sent to clinical teams. Patients meeting these criteria were referred to the researchers, who subsequently approached the patients to explain the study and obtain informed consent. Once consent had been given, patients met with a RA to complete screening measures for ADHD and data were extracted from the clinical records. Four patients in the SMI category consented to participate in the study and met with researchers, but did not consent for their records to be accessed. Hence, there were missing data for these participants.
If a patient screened positive on the BAARS-IV scales (self-rated scales for current and retrospective ADHD symptoms), they were invited to participate in a diagnostic interview. These interviews were administered by a RA who had received training, including observation of these assessments by qualified staff in a clinical setting; specific training by qualified and experienced clinicians who routinely administer the interviews; and practice ratings of recorded clinical interviews to a point of reliability and convergence of ratings. For patients who were positive on the clinical diagnostic interview for ADHD, an informant interview was conducted with the patient’s primary nurse to supplement information from the self-report interview. Once completed, materials for each case were reviewed by a consultant psychiatrist (PA) from the Maudsley Hospital Adult ADHD service.
Behavioural function
Critical incidents were obtained from clinical records recorded by staff over the previous 12-month period. The data were grouped based on harmful impact on others: (1) ‘no harm incidents’ including security issues, verbal aggression and physical injury not requiring treatment or (2) ‘harmful incidents’, classified as any physical injury requiring further assessment or treatment. There were no critical incidents involving grievous bodily harm or homicide during the 12-month period. Seclusion data were obtained from clinical records recorded by staff over the previous 12-month period and categorised by number of episodes and duration of time in seclusion.
Results
Comorbid diagnoses
All participants had a DSM-IV primary diagnosis of SMI (n = 81, 60.90%) or PD (n = 52, 39.10%). Four patients in the SMI category denied us access to records so we were unable to specify their primary diagnosis, offence history, ethnicity, age, critical incidents, episodes and duration of seclusion. The SMI category consisted of patients with a primary diagnosis of psychotic (n = 71, 92.21%) or bipolar disorders (n = 6, 7.79%). The PD category consisted of patients with a primary diagnosis of borderline (n = 24, 46.15%), antisocial (n = 23, 44.23%), schizoid (n = 3, 5.77%), narcissistic (n = 1, 1.92%) or histrionic (n = 1, 1.92%) PD. In common with all forensic mental health settings, there were high rates of comorbidity within the sample; however, only six patients had a history of ADHD recorded in their records (three in the SMI category and three in the PD group), and none had a current diagnosis or was receiving medication for ADHD at the time.
Age, ethnicity and history of offences
Most SMI patients were male (n = 79, 97.53%), with ethnicity classified as white (n = 39, 50.65%), black (n = 32, 41.56%), Asian (n = 2, 2.60%) or mixed race (n = 4; 5.19%). In the PD category, all patients were male (n = 52), with 47 (90.38%) classified as white, two (3.85%) as black, one (1.92%) as Asian and two (3.85%) as mixed race. Participants were aged between 19.3 and 64.3 years with no significant difference in age between the SMI (mean 37.10 years, SD 10.69 years) and PD categories (mean 40.26 years, SD 11.19 years) [t(129) = –1.62; p = 0.11]. Nearly all the participants had a history of violence (n = 96, 74.42%) and/or sexual violence (n = 26, 20.16%). Other offences (n = 7, 5.43%) included arson, burglary and driving offences.
Prevalence estimates
One hundred and thirty-three patients completed the ADHD child and current screeners (SMI, n = 81; PD, n = 52). Compared with patients in the SMI group, in the PD group patients had significantly higher BAARS-IV current total scores [SMI: mean 12.00, SD 9.93; PD: mean 15.92, SD 15.92, t(133) = –2.11; p = 0.04] and childhood scores [SMI: mean 16.59, SD 13.89; PD: mean 27.41, SD 15.07, t(133) = –2.11; p = 0.00].
Twenty-six patients (19.55%) screened positive for ADHD on the BAARS-IV scales and were offered a clinical diagnostic interview. Seven (8.64%) patients had a primary diagnosis of SMI and 19 (36.53%) had a primary diagnosis of PD. Three patients refused further assessment with a clinical diagnostic interview; thus, 23 of the screen-positive participants completed a DIVA (SMI, n = 6; PD, n = 17). Following the DIVA assessment, four participants (23.52%) in the PD category showed persistent ‘syndromatic’ ADHD (one with hyperactive–impulsive type and three with combined type). When applying the more relaxed ‘symptomatic’ criteria, six participants (35.29%) in the PD group had persisting symptoms (three hyperactive–impulsive type and three combined type). Of the six participants in the SMI category who screened positive, none met criteria for either ‘syndromatic’ or ‘symptomatic’ ADHD. Hence, subsequent analysis was conducted on only the PD group.
Self-rated impairments
The forensic patients who met clinical and symptomatic criteria for ADHD (n = 6) and those who screened positive for ADHD (n = 19) rated themselves as significantly more impaired than forensic psychiatry patients who screened negative for ADHD, with a large effect size for all items except for money management (). Significant positive correlations were also seen between ADHD symptom scores (in adulthood and childhood) and all domains of self-reported impairment ().
Barkley Adult ADHD Rating Scale – IV impairment scores, critical incidents and seclusion data, comparing PD patients screening negative for ADHD with positive screening ADHD patients and DIVA-positive patients
Correlations for the PD patients between screener scores, BAARS-IV impairment data, critical incidents and seclusion data
Critical incidents and seclusion
Critical incident and seclusion data taken from prison records did not show a significant difference (albeit we found trend to higher rates in ADHD cases; p = 0.07). This perhaps reflects the serious nature of the comorbid disorders and behavioural problems, other than those related to ADHD, in this high-risk population and the small sample of identified ADHD cases. Using the broader category of screen-positive cases, there was a significant increase in hours spent in seclusion compared with the screen-negative group (see ).
Discussion
We set out to investigate rates of ADHD in mentally disordered offenders and quantify functional outcomes for these patients in institutional settings. In the SMI group, seven patients scored above threshold on the ADHD screeners, but none fulfilled criteria for ADHD on further assessment. In the PD group, 19 patients screened positive for ADHD. Out of 17 screen-positive PD patients interviewed with the DIVA, six were categorised as having ADHD. This gives an overall estimated prevalence of 8.6% for syndromatic ADHD and 12.9% for symptomatic ADHD, which is two to four times higher than the DSM-IV rate of ADHD (estimated from previous studies to lie in the region of 2.5–4.3% in the adult population97,101,113). Despite the high level of ADHD in the PD group, none of the patients were recognised as having ADHD at the time of the research assessments.
The absence of ADHD within the SMI group suggests that there is no particular association among offenders between ADHD and psychotic disorders, mainly schizophrenia in this sample. This finding suggests that a detailed diagnostic assessment of ADHD should be able to distinguish between ADHD and schizophrenia in most cases and that schizophrenia does not usually generate an ADHD-like syndrome. If this finding generalises to non-forensic psychiatric populations, it increases the likelihood that when ADHD symptoms and impairments are seen in someone with a history of psychosis, they probably reflect two independent co-occurring conditions. Further research is needed to clarify this question.
The screening rate of 36.5% for ADHD in the PD group is consistent with previous reports in a PD population.107 The screening approach applied in this study had moderate sensitivity within the PD group, whereas it seemed to be less helpful within the SMI population, among which none of the screen-positive participants met clinical criteria for ADHD.
A second aim of the study was to determine the functional impairment of patients with comorbid ADHD compared with their non-ADHD-detained peers in a forensic setting. Overall, significantly greater impairment was reported across all personal, social and occupational domains among the PD and ADHD group compared with those without ADHD, mostly with large effect sizes. ADHD symptoms, both childhood and current, were positively correlated with self-rated impairment.
More specifically, significant differences between groups were found for self-rated impairment across all domains with the exception of money management, which most likely reflects the fact that this environment provides little opportunity for self-management of financial affairs. For the same reasons, patients omitted to complete items on the BAARS-IV impairment scales (e.g. many patients did not attend educational and/or occupational activities). There was wide variation in frequency of incidents, episodes and hours of seclusion. Nevertheless, there was a trend among the comorbid ADHD and PD patients to have a higher number of seclusion interventions and to spend more time in seclusion than their peers. These findings suggest that the staff were more likely to use seclusion to manage PD and ADHD patients than their non-ADHD peers and that the former require more hours in seclusion once this intervention has been applied. This may indicate that, once aroused, individuals with ADHD look agitated and take longer to calm down. This is supported by the finding that level of observed agitation and younger age have been found to be significant predictors of the use of seclusion on psychiatric wards.136 Further studies are required to establish whether or not treatment of ADHD in these patients will lead to a change in behaviour reflected in a reduction of hours in seclusion.
There was no significant difference between groups in critical incident data, nor was there a significant correlation between ADHD symptoms, incidents and seclusion data. This finding is inconsistent with that reported previously for offenders detained in mental health and prison settings.20,107,137 The present study included a high proportion of patients detained in high security (69%) where, due to stringent security procedures and sanctions, a relatively low base rate of acting out behaviours are found. Furthermore, it might be the case that for the individuals held within the high-security hospital, other mental health disorders create a comparable degree of behavioural problems regardless of the underlying diagnosis.
Overall, the current study strengthens our understanding of the comorbidity and behavioural consequence of ADHD in adult forensic mental health settings. An advantage of the current research is that it was conducted in a naturalistic setting with patients who have complex presentations and high comorbidity. Furthermore, objective clinical records were used to obtain functional outcomes and diagnostic status was established by comprehensive clinical interviews rather than screening measures.
Strengths and weaknesses
The study is limited by its small sample size, which is partly due to the high rate of refusal (46%), something that is difficult to avoid in the settings investigated. Hence, the sample may be biased as some patients may have refused to participate in a lengthy clinical assessment (including the completion of screening questionnaires) because of problems with attention span and other symptoms associated with ADHD, such as irritability.94 Alternatively, those with ADHD symptoms might have been more interested in taking part in the study. These considerations might have resulted in a non-representative sample, which was underpowered to detect some of the impairments, such as critical incidents, in within-group analysis. A further limitation is that we did not interview those individuals who screened negative for ADHD, so the specificity of the screening tool in this population remains unknown. Despite these limitations, the use of the DIVA diagnostic interview gives confidence in the finding of high rates of ADHD in the PD group. DIVA is designed to establish the presence or absence of each of the 18 DSM-IV symptoms for ADHD during both childhood and adulthood, in addition to the essential age at onset, situational pervasiveness, symptom chronicity and impairment criteria. As such, it is expected to give lower prevalence rates than the use of symptom rating scales alone. A potential limitation is the ability to accurately identify ADHD symptoms retrospectively when relying on self-report data alone, although in the context of this study this would lead to more conservative estimates of prevalence. Future studies would benefit from diagnostic interviews for ADHD in a wider range of patients and further work to improve on effective screening tools in forensic mental health populations.
