© 2007 The Royal College of Psychiatrists
Mental ill-health in adults with intellectual disabilities: prevalence and associated factors
Section of Psychological Medicine, Division of Community Based Sciences, University of Glasgow
Learning Disabilities Partnership, NHS Greater Glasgow and Clyde
Section of General Practice and Primary Care
Section of Psychological Medicine
Section of Psychological Medicine, Division of Community Based Sciences, University of Glasgow, Glasgow, UK
Correspondence: Professor Sally-Ann Cooper, Academic Centre, Gartnavel Royal Hospital, 1055 Great Western Road, Glasgow G12 0XH, UK Tel: +44 (0)141 211 0690; fax: +44 (0) 141 357 4899; email: SACooper{at}clinmed.gla.ac.uk
Declaration of interest None. Funding detailed in Acknowledgements.
 TOP ABSTRACT INTRODUCTIONMETHODRESULTSDISCUSSIONACKNOWLEDGMENTSREFERENCES |
|---|
Background Reported prevalence of mental ill-health among adults with intellectual disabilities ranges from 7 to 97%, owing to methodological limitations. Little is known about associations.
Aims To determine the prevalence of mental ill-health in adults with intellectual disabilities and to investigate factors independently associated with it.
Method Population-based study (n=1023) with comprehensive individual assessments modelled using regression analyses.
Results Point prevalence of mental ill-health was 40.9% (clinical diagnoses), 35.2% (DC–LD), 16.6% (ICD–10–DCR) and 15.7% (DSM–IV–TR). The most prevalent type was problem behaviours. Mental ill-health was associated with more life events, female gender, type of support, lower ability, more consultations, smoking, incontinence, not having severe physical disabilities and not having immobility; it was not associated with deprived areas, no occupation, communication impairment, epilepsy, hearing impairment or previous institutional residence.
Conclusions This investigation informs further longitudinal study, and development of appropriate interventions, public health strategy and policy. ICD–10–DCR and DSM–IV–TR undercount mental ill-health in this population compared with DC–LD.
|
TOPABSTRACTINTRODUCTIONMETHODRESULTSDISCUSSIONACKNOWLEDGMENTSREFERENCES |
|---|
The prevalence of mental ill-health among adults with intellectual disabilities is unknown. Existing studies have methodological limitations, accounting for the wide discrepancy in reported prevalence rates which range from 7 to 97% (Wright, 1982; Borthwick-Duffy & Eyman, 1990; Linaker & Nitter, 1990; King et al, 1994). Limitations have included biased sampling; reliance upon existing case-note information or instruments designed as screening tools only; lack of information on the extent of detail within assessments, the instruments or the diagnostic criteria used; and in population-based studies, small cohort sizes. Other limitations include failure to indicate whether rates are lifetime or point prevalence; reporting combined prevalence for children and adults; reporting mental ill-health in total, but not describing or being comprehensive as to what is included; and studying selected subgroups such as adults only with verbal communication skills. These limitations prevent replication of findings, and account for the current confusion within the existing literature. Apart from behavioural phenotypes, little is known of the factors associated with mental ill-health in adults with intellectual disabilities (Smiley, 2005).
We report here the findings from a large-scale population-based study with clearly described methods, which was conducted to determine the prevalence of mental ill-health among adults with intellectual disabilities and to investigate the factors independently associated with mental ill-health.
|
TOPABSTRACTINTRODUCTIONMETHODRESULTSDISCUSSIONACKNOWLEDGMENTSREFERENCES |
|---|
Ethics
The project was approved by the relevant research ethics committee. Individual consent to participate was taken from each person with intellectual disabilities as far as that person had decision-making capacity to consent, with assent given by the nearest carer when the participant lacked such capacity.
Case ascertainment
A process of case ascertainment was conducted in the Greater Glasgow Health
Board area of Scotland. Identification of all adults with intellectual
disabilities aged 16 years and over was determined through social work
services for people with intellectual disabilities; local authority funding
arrangements for persons receiving paid support of any kind, including day
opportunities; local specialist health services for people with intellectual
disabilities; the Health Board; the Scottish Executive Statistical Department;
and primary healthcare services. Over the period 2002–2004, all of
Greater Glasgow’s general practitioners and family physicians
(n=631) worked with the project, and were paid an item-of-service fee
for each person with intellectual disabilities whom they identified as
registered with them and within the project remit. This process led initially
to an over-identification of possible participants, such as people with IQ
scores in the 70–80 range and additional complex health needs; such
individuals were excluded from the research. We believe the case ascertainment
process to have been comprehensive: a rate of 3.33 per 1000 adult general
population was yielded, which is similar to other large-scale case
ascertainments (Farmer et al,
1993; McGrother et
al, 2001).
Process
Each participant underwent a detailed assessment by one of a team of six
registered nurses, who had specialist qualifications in working with adults
with intellectual disabilities and who were trained in the use of the
assessment instruments, and one of three general practitioners, who had a
special interest in working with adults with intellectual disabilities. They
reviewed each participant’s primary healthcare case notes using a
semi-structured format, then undertook a detailed face-to-face assessment with
each participant, supported by their paid or family carer. In all cases,
assessments completed by the nurses were discussed with one of the three
general practitioners. Participants identified as possibly, probably or
definitely having mental ill-health were notified to the project
psychiatrists, who were specialists in working with adults with intellectual
disabilities. These psychiatrists undertook in each case a review of the
current and previous intellectual disabilities psychiatry, general psychiatry,
child psychiatry and psychology case notes where such notes existed and (where
indicated) other secondary physical healthcare case notes, and conducted
psychiatric assessments of the person with intellectual disabilities,
supported by one or more carers, for diagnostic clarification. Diagnoses were
derived according to clinical, DC–LD
(Royal College of Psychiatrists,
2001), ICD–10–DCR
(World Health Organization,
1993) and DSM–IV–TR
(American Psychiatric Association,
2000) diagnostic criteria.
Materials
The assessments were conducted using the following measures.
Primary healthcare form
A purpose-designed, semi-structured form to review primary healthcare case
notes was completed to provide essential background information necessary to
inform psychiatric assessment.
PAS–ADD Checklist
The Psychiatric Assessment Schedule for Adults with Developmental
Disabilities (PAS–ADD) Checklist
(Moss et al, 1998)
was designed as a mental health screening tool for use with adults with
intellectual disabilities. As its specificity was not relevant in this
project, in order to improve its sensitivity from that previously reported
(Moss et al, 1998;
Simpson, 1999;
Sturmey et al, 2005),
and following a pilot exercise with 50 people
(Curtice et al,
2001), we used a lower cut-off threshold of any two symptoms
(excluding specific phobias) or any one high-risk symptom, which we defined to
include the items for suicidal attempts or thoughts, persecutory behaviour,
and hallucinations or delusions, and we counted identified symptoms whether or
not they were thought by the carer to be a problem (unlike the standard
scoring procedure of the PAS–ADD Checklist at the time).
C21st Health Check
The C21st Health Check (Glasgow
University Affiliated Programme, 2001) includes assessment
sections on mental ill-health, problem behaviours, autistic-spectrum
disorders, developmental level and support needs, as well as general physical
health, and has been demonstrated to have good utility
(Curtice et al,
2001). It also has a section for a selected physical examination,
including assessment of vision and hearing. The sections on mental ill-health,
problem behaviours and autistic disorders were used to trigger referral for
full psychiatric assessment of participants who scored below our cut-off value
on the PAS–ADD Checklist. Assessment of physical health was necessary to
exclude any possible physical cause of apparent psychiatric presentation, and
measurement of physical health items provided data for statistical
investigation of associations with mental ill-health.
Demographic data
A purpose-designed demographic form was used to collect information on the
demographic factors to be investigated, including full postcode information,
from which an area-based measure of socio-material deprivation was derived,
using the Carstairs index which is in widest use for this purpose in Scotland
(Carstairs & Morris,
1989).
Blood testing
A phlebotomy protocol was established to ensure (for example) that every
person with Down syndrome had up-to-date thyroid function testing. This was
necessary to exclude possible physical causes of psychiatric
presentations.
Full psychiatric assessment
Individuals who were referred for full psychiatric assessment were
additionally investigated with the following instruments:
- a purpose-designed semi-structured form to review case notes for essential
current and background information;
- a comprehensive semi-structured assessment format with consultant-level
diagnoses;
- the Present Psychiatric State for Adults with Learning Disabilities
(PPS–LD; Cooper, 1997); a
semi-structured psychopathology schedule specifically designed for use with
adults with intellectual disabilities, which now allows classification of
psychopathology by clinical, DC–LD, ICD–10–DCR, and
DSM–IV–TR criteria;
- purpose-designed instruments containing items to detect the psychopathology
listed in autistic-spectrum disorders and hyperkinetic disorders contained
within DC–LD, ICD–10–DCR, and DSM–IV–TR, and
also problem behaviours as defined by DC–LD; these were designed to be
used within the context of a full psychiatric assessment, and suitable for use
by trained psychiatrists;
- the Test for Severe Impairment (Albert
& Cohen, 1992); this provides an assessment of current
cognitive ability, an overview of which can be compared with information
available from case notes and informants;
- the Vineland Scale (Survey Form)
(Sparrow et al,
1984); this provides a measure of current level of adaptive
functioning and was also used to measure best-ever level of functioning, in
cases where functional level had regressed; it was included to assess ability
level in keeping with ICD–10–DCR criteria, and to contribute in
part to the assessment of dementia.
Determination of ability level
Level of intellectual ability was determined by scores on the Vineland
Scale (Survey Form) and results of previous IQ tests recorded in case notes
and primary care records. The C21st Health Check includes a section which
measures developmental level through a series of questions on the
person’s skills and support needs. Total scores are highly correlated
with developmental age as measured by the Vineland Scale (Survey Form):
Pearson’s correlation r=0.812; P<0.001. The C21st
Health Check additionally requires the professional to apply clinical
judgement if the skills and support needs score is lowered because of
non-cognitive factors such as cerebral palsy. A level of ability in keeping
with the ICD–10–DCR classification is therefore derived. In this
study, for participants who did not have a Vineland Scale (Survey Form)
completed nor a record of previous IQ testing, the assessed level of ability
from the C21st Health Check was used. For people whose skills had declined
(e.g. because of dementia or schizophrenia), a retrospectively completed
‘best-ever’ Vineland Scale score was used rather than the current
score.
Determination of mental health status
The semi-structured interview format followed by the psychiatrists was
comprehensive and in keeping with best practice; more detailed information on
such assessments of mental ill-health in persons with severe and profound
intellectual disabilities has been reported elsewhere
(Cooper, 2003). The assessment
included at least one face-to-face meeting with the person with intellectual
disabilities, and also with the person’s main carer. If the latter was a
paid carer, parents or other close relatives were also interviewed if
available. Information was sought from additional paid carers as required:
typically this depended upon the length of time the main paid carer had known
the person and the level of detail of current and background information known
to that carer. Previous and current case notes were also reviewed by the
psychiatrists. The first appointment was scheduled for a 1.5 h duration, and
subsequent appointments arranged as required until all necessary information
had been collected about current psychopathology, its severity and duration,
and differentiation between longstanding characteristics and symptoms of
mental ill-health, rated within the context of the person’s overall
developmental level, using the rating scales. Information was also collected
on the participant’s past psychiatric history, previous and current
medical history, current and previous drug use and mental health
interventions, past and current medical and psychiatric history of family
members, personal background, social circumstances and social networks,
developmental history and current developmental level, and personality
development. A mental state examination was conducted. Physical health had
already been assessed. The information from the sources was integrated,
clinical diagnoses were determined by consultant psychiatrists specialised in
working with adults with intellectual disabilities, and psychopathology was
classified using the three diagnostic classificatory systems.
Analyses
Data were entered onto a personal computer and analysed using the
Statistical Package for the Social Sciences version 11.5 for Windows.
Frequency data were derived for point prevalence rates. Associations were
investigated between each of 20 variables – age; gender; marital status;
level of ability; presence of visual impairment; presence of hearing
impairment; presence of epilepsy; presence of severe physical disabilities
(quadriplegia); presence of mobility impairment; presence of communication
impairment; presence of incontinence of urine; presence of incontinence of
bowels; type of living or support arrangement; whether previously a long-stay
hospital resident, area-based measure of deprivation for the area in which the
person lived; whether the person had any type of daytime occupation; number of
consultations with the general practitioner or family physician within the
preceding 12-month period; number of hospital admissions in the preceding
12-month period; number of life events in the preceding 12-month period;
whether the person smoked – with whether or not the person had mental
ill-health of any type (excluding autistic-spectrum disorder and specific
phobias). Autistic-spectrum disorders were excluded from the analyses because
such developmental disorders with onset in early childhood and continuation
thereafter throughout life were conceived as possibly differing from mental
ill-health with onset in adolescence or adulthood; participants with
autistic-spectrum disorder were only included in the mental ill-health
category if they additionally had a point prevalence of other mental
ill-health of any type, excluding specific phobia. Binary logistic regression
analysis was undertaken to determine the factors independently associated with
the dependent variable ‘mental ill-health of any type’ (excluding
autistic-spectrum disorder and specific phobias). The backwards stepwise model
was used with likelihood ratio tests determining statistical significance for
removal of each factor. At each step, the regressor with the smallest partial
correlation was removed if it met the removal criterion, which was set at
0.05. The analyses were then repeated for the group of participants with
moderate to profound intellectual disabilities only.
|
TOPABSTRACTINTRODUCTIONMETHODRESULTSDISCUSSIONACKNOWLEDGMENTSREFERENCES |
|---|
Cohort characteristics
Assessments were completed for 70.6% of the total eligible adult population with intellectual disabilities, among whom valid consent or assent for research was recorded for 92.7%. The resultant cohort of 1023 adults comprised 562 men (54.9%) and 461 women (45.1%) and had a mean age of 43.9 years (range 16–83). Levels of ability ranged from mild in 398 (38.9%), through moderate in 248 (24.2%) and severe in 193 (18.9%), to profound intellectual disabilities in 184 (18.0%). Of this cohort 390 (38.1%) lived with a family carer, 467 (45.7%) lived with paid support, 102 (10.0%) lived independently of paid support and 64 (6.3%) lived in a congregate care setting, such as a nursing home designed to care for older, frail people. Most of the cohort (95.7%) were single and 96.4% were White. For 186 (18.2%) participants the cause of their intellectual disabilities was Down syndrome.
Of the 1023 adults, 552 (54.0%) were identified by the assessment as possibly, probably or definitely having mental ill-health, and 517 (93.7% of these 552 individuals or 50.5% of the whole cohort) were notified to and reviewed by the intellectual disabilities psychiatrists. Of these 552 participants, 277 (50.2%, or 27.1% of the whole cohort) were already receiving care from an intellectual disabilities psychiatrist or psychologist at the time of the assessment. The 35 (3.4%) non-notified participants had been identified at the assessment as having minor problem behaviours only.
Prevalence of mental ill-health
Table 1 reports the point
prevalence rates of mental ill-health in the cohort. Findings are presented
separately for diagnoses using clinical, DC–LD, ICD–10–DCR
and DSM–IV–TR diagnostic criteria. The terms used in the table to
describe the diagnostic categories are not identical to those used in all the
diagnostic manuals as they differ between the manuals, but the correct
operational diagnostic criteria as outlined in each manual are used. Only
diagnostic categories where the diagnostic criteria are operationalised were
included, hence (for example) DC–LD ‘other’,
ICD–10–DCR ‘other’, and DSM–IV–TR
‘not otherwise specified’ (NOS) categories were not included,
except where criteria were cited (as these ‘other’ and
‘NOS’ categories are essentially clinical diagnoses).
|
View this table: [in a new window] | Table 1 Point prevalence rates of mental ill-health as defined by clinical, DC–LD, ICD–10–DCR, and DSM–IV–TR diagnostic criteria |
Specific phobias were excluded from our prevalence rates, as were previous episodes of ill-health that had resolved by the time of the assessment, with the exception of schizophrenia/schizoaffective disorder, currently in remission, and bipolar affective disorder, currently euthymic, which we included in the reported rates. Our category of ‘mental ill-health of any type’ follows these same inclusion/exclusion rules. Table 2 provides details of the diagnoses within categories that were sought: no one within the cohort was found to be in episode with some of the disorders that were sought, e.g. DSM–IV–TR brief psychotic disorder and alcohol-induced psychotic disorder. Mild as well as severe problem behaviours are included in that category, accounting for the high prevalence rate in women.
|
View this table: [in a new window] | Table 2 Disorders included within each of the diagnostic categories |
Some participants met criteria for more than one disorder: 605 participants (59.1%) had no clinical diagnosis, 297 (29.1%) had one, 94 (9.2) had two, 25 (2.4%) had three and 2 (0.2%) had four clinical diagnoses. The breakdown of diagnoses within the overarching diagnostic groupings shown in Table 1 necessarily vary by the diagnostic classification used, as these differ between the systems. The following breakdown refers to clinical diagnoses. For affective disorders (6.6% of the cohort), 4.1% were unipolar depressive episodes, 0.5% were bipolar depressive episodes, 0.6% were manic episodes, 1.2% were bipolar disorder in which the participant was euthymic at the time of assessment, and 0.3% were cyclothymic disorder. Within the psychosis category, 2.9% were schizophrenia in episode, 0.4% were schizophrenia in remission, 0.2% were schizoaffective disorders in episode and 0.9% were other types of non-affective psychosis, in episode. In the anxiety category, 1.7% were generalised anxiety disorder, 0.7% were agoraphobia, 0.3% social phobia, 0.5% adjustment disorder, 0.3% post-traumatic stress disorder, 0.2% panic disorder, 0.2% mixed anxiety and depression and 0.2% other anxiety disorders (where the breakdowns do not appear to sum to the point prevalence for the overarching category, this is owing to the figures being rounded to one decimal place).
Table 3 reports point prevalence rates of clinical diagnosis of mental ill-health for the 1023 adults by gender and by ability level. As in Table 1, specific phobias are excluded; schizophrenia/schizoaffective disorder, currently in remission and bipolar affective disorder currently euthymic are included, but all other previous episodes of mental ill-health which were resolved by the time of the assessment were excluded.
|
View this table: [in a new window] | Table 3 Point prevalence rates of clinical diagnosis of mental ill-health at different ability levels and by gender |
Associations with mental ill-health
For the whole cohort of 1023 participants, the factors found to be
independently associated with mental ill-health of any type (excluding
autistic-spectrum disorders and specific phobias) were as follows: having
profound intellectual disabilities; having severe intellectual disabilities;
having experienced a higher number of life events in the preceding 12-month
period; having a higher number of consultations with the general practitioner
or family physician in the preceding 12-month period; being a smoker; living
with paid carer support; not having severe physical disabilities; not having
immobility; having urinary incontinence; and being female. The other variables
were not found to be independently associated with mental ill-health
(Table 4).
|
View this table: [in a new window] | Table 4 Factors retained within the model as independently associated with clinical diagnosis of mental ill-health (excluding specific phobias and autistic-spectrum disorder) |
For the 625 participants with moderate to profound intellectual disabilities, the items retained within the regression model as independently associated with mental ill-health of any type (excluding autistic-spectrum disorders and specific phobias) were as follows: having experienced a higher number of life events in the preceding 12-month period; having urinary incontinence; not having severe physical disabilities; not having immobility; being female; having profound intellectual disabilities; having a higher number of consultations with the general practitioner or family physician in the preceding 12-month period; and being a smoker. Other variables were not independently associated with mental ill-health (Table 5).
|
View this table: [in a new window] | Table 5 Factors retained within the model as independently associated with clinical diagnosis of mental ill-health (excluding specific phobias and autistic-spectrum disorder) for people with moderate to profound intellectual disabilities |
|
TOPABSTRACTINTRODUCTIONMETHODRESULTSDISCUSSIONACKNOWLEDGMENTSREFERENCES |
|---|
Mental ill-health is common among adults with intellectual disabilities. We found that more than a third – 40.9% (clinical diagnoses) or 35.2% (DC–LD diagnoses) – of our cohort had mental ill-health. These point prevalence rates are higher than those observed in the UK general population (Singleton et al, 2001). Many methodological factors will affect reported point prevalence rates, including the diagnostic criteria that are employed. This study is population-based and we measured a comprehensive range of psychopathology using semi-structured instruments and detailed assessments. Hence, the amount of psychopathology that we detected represents that occurring in the adult population with intellectual disabilities. Operationalised diagnostic criteria have the advantage of being explicit, and thus increase reliability of diagnosis. It is, however, essential that these criteria are also valid and provide an accurate description of the presentation of each mental disorder. We conclude, in the absence of any identified diagnostic laboratory test or other elucidating research such as studies of prognostic validity, that at present the most appropriate operationalised diagnostic criteria are those that most closely resemble the current ‘gold standard’ of clinical diagnosis by a specialist, provided comprehensive assessments and measurements have been used (as outlined) and that they are conducted with a population-based sample. We found considerably lower prevalence rates using ICD–10–DCR and DSM–IV–TR diagnostic criteria, which, as highlighted by previous researchers (Sturmey, 1995; Einfeld & Tonge, 1999), do not take account of the pathoplastic effect of developmental level on the psychopathology within categories of mental disorders (and so, although representing the presentation of psychopathology within mental disorders in the general population, do not accurately represent the presentation in the population with intellectual disabilities). This finding was most marked for problem behaviours and was present across all diagnostic categories, with the exception of alcohol and substance use disorders.
There are many possible biological, psychological, social and developmental factors that might account for the high prevalence rates of mental ill-health in this population, and with the exception of behavioural phenotypes, these largely have not been investigated. We identified some similarities with the general population in terms of the factors independently associated with mental ill-health – such as experiencing a higher number of preceding life events, having a higher number of preceding general practitioner or family physician consultations, being female, and being a smoker – but also some differences. Examples of these differences were the lack of association between living in more deprived areas, not having any daytime occupation, marital status and epilepsy, and mental ill-health. These differences are important, as public health interventions to improve the mental health of nations will fail to address the needs of adults with intellectual disabilities, and hence widen the existing inequality gap, if they are focused only on areas that are of importance to the general population. Interestingly, having communication impairment was not independently associated with mental ill-health whereas having a lower developmental level was, suggesting that the higher prevalence of mental ill-health at lower ability levels cannot be explained by communication alone. Having previously been a long-stay hospital resident was not associated with mental ill-health, whereas having incontinence and not having severe physical disabilities nor immobility were. Whether the association between type of living support and mental ill-health is a result of cause or effect is unclear; either mental ill-health is an important cause of the requirement for expensive support packages, or mental health needs are being precipitated or not optimally managed in these settings. Either explanation highlights a need for healthcare professionals to work closely with paid support workers and managers of support-providing organisations.
Our findings offer provisional guidance to identifying people within the adult population with intellectual disabilities who are at higher risk of having mental ill-health and might benefit from more proactive healthcare approaches, and also are a step towards developing interventions that might be of benefit, such as supporting people who experience life events, and screening for and managing incontinence.
Comparisons with previous research
Because of the methodological limitations outlined above, there are few
previously published prevalence studies with which these results can be
compared. Previous small-scale population-based studies include those of Lund
(1985) (n=302);
Cooper & Bailey (2001)
(n=207); and Deb et al
(2001) (n=101), the
last of which included only participants with verbal communication skills and
hence is not comparable. The larger-scale study of Taylor et al
(2004) (n=1155)
reported data from a psychiatric screening tool only, rather than presenting
psychiatric diagnoses, and hence is also not comparable. The population-based
study by Corbett (1979)
(n=402) did not have the advantage of operationalised diagnostic
categories, reporting by ICD–8
(World Health Organization,
1968), nor did it use clear methods of assessment. The study
reported by Lund (1985) used
assessment methods which, given subsequent health technology advances, would
today be considered rather limited. Both studies
(Corbett, 1979;
Lund, 1985) include some
individuals whose IQ measurements actually place them outside the intellectual
disabilities range. Although we recognise these limitations in the existing
literature, in Table 6 we
compare, as far as possible, the findings from our study with those of Corbett
(1979), Lund
(1985) and Cooper & Bailey
(2001). Access to the original
data in the latter study has enabled us to present a prevalence rate for
mental ill-health of any type, defined in the same way as in our study. This
tentative comparison shows a high point prevalence of mental ill-health to be
a feature of all the studies except that of Lund.
|
View this table: [in a new window] |
Table 6 Comparison of studies: point prevalence rates of mental ill-health
|
Associations have been previously demonstrated between preceding life events in adults with intellectual disabilities and ‘affective/neurotic disorders’ as defined by a screening tool (Hastings et al, 2004), and between life events and scores on the Developmental Behaviour Checklist for Adults (Hamilton et al, 2005), but the effect of life events in this population has received little other attention. The relationship between ability level and mental ill-health has variously been reported to be absent (Corbett, 1979), present with higher prevalence of mental ill-health at lower ability levels (Lund, 1985; Cooper & Bailey, 2001), or present with higher prevalence of mental ill-health at higher ability levels (Borthwick-Duffy & Eyman, 1990; Bouras & Drummond, 1992); these differences are explained by the methodological limitations described above. The previous reports have also presented inconsistent and conflicting results regarding possible associations between mental ill-health and age, physical disability or epilepsy (Smiley, 2005); most studies have not found any association between gender and mental ill-health in this population, unlike the general population, although Taylor et al (2004) did find that women had higher scores than men on their ‘affective/neurotic disorders’ sub-domain, but not on their other two sub-domains. The results of our investigations therefore largely present new findings.
Strengths and limitations of our study
The strengths of this study include its comprehensive case ascertainment
procedures, the large size of the cohort, the high level of agreement to
participate in the study, detailed individual assessments, and mental
ill-health data reported by clinical, DC–LD, ICD–10–DCR, and
DSM–IV–TR diagnostic criteria. Limitations include the case
ascertainment for people with mild intellectual disabilities, many of whom
require support for learning during their school years but become
‘invisible’ in adulthood, having gradually acquired the skills to
live independently with marital and live-in partners, hold down paid
employment and raise a family. Our procedures will have failed to fully
identify this group, that is individuals who do not access any services or
supports, and whose general practitioners/family physicians have not
recognised their intellectual disabilities and who do not have a record of
intellectual disability in primary healthcare case notes. For people with
moderate to profound intellectual disabilities, we are confident that our
procedures will have identified this population fully. In our presentation of
results, we have acknowledged and addressed this limitation by presenting
results separately for the group with moderate to profound intellectual
disabilities, as well as for the whole cohort: the factors we found to be
associated with mental ill-health were similar for both. A further limitation
is the incompleteness of some previous case-note entries, limiting the amount
of past history information available. Our study is also limited by its
cross-sectional design; hence we report independent associations with mental
ill-health, rather than independent predictors or aetiological factors for
such ill-health.
Implications and future directions
Intellectual disability is common and lifelong, with the lifetime cost (in
excess of the costs for people without intellectual disabilities) in the USA
for the year 2000 incident cohort being estimated at $44.1 billion
(Honeycutt et al,
2003). Not surprisingly, people with intellectual disabilities
have been the focus of recent major national policy developments in Europe,
the USA, Australia and across the high-income countries, but with little
research evidence to inform these developments. Mental ill-health is a
significant contributor to costs and quality of life. People with intellectual
disabilities experience health inequalities compared with the general
population; these include a shorter life expectancy, higher level of comorbid
health needs and a higher proportion of ‘hidden’ comorbid health
needs which fail to be met by services
(Cooper et al, 2004;
NHS Health Scotland, 2004;
Scheepers et al,
2005). The full extent to which inequalities are accounted for by
modifiable or preventable factors has been unclear owing to lack of
investigation, and the study reported here is an important step towards a
better understanding of the probably multiple contributory interacting
factors. It will be important in future to report longitudinal cohort studies,
from which predictive and aetiological factors for mental ill-health can be
determined and utilised to influence the development of interventions, public
health strategy, and health and social care policy, appropriate to the needs
of this population.
|
TOPABSTRACTINTRODUCTIONMETHODRESULTSDISCUSSIONACKNOWLEDGMENTSREFERENCES |
|---|
We thank the study participants and their paid and family carers for participating in this study. We are grateful to the nurses and doctors in Greater Glasgow who were involved in the study, and for secretarial support provided by Elaine Newell and Afshan Fairley. The study was funded by the Greater Glasgow Health Board and the West of Scotland Research and Development Mental Health Programme.
|
TOPABSTRACTINTRODUCTIONMETHODRESULTSDISCUSSIONACKNOWLEDGMENTSREFERENCES |
|---|
- Albert, M. & Cohen, C. (1992) The Test for Severe Impairment: an instrument for the assessment of people with severe cognitive dysfunction. Journal of the American Geriatric Society, 40, 449 –453.
- American Psychiatric Association (2000) Diagnostic and Statistical Manual of Mental Disorders (4th edn, revised) (DSM–IV–TR). APA.
- Borthwick-Duffy, S. A. & Eyman, R. K. (1990) Who are the dually diagnosed? American Journal on Mental Retardation, 94, 586 –595.[Medline]
- Bouras, N. & Drummond, C. (1992) Behaviour and psychiatric disorders of people with mental handicaps living in the community. Journal of Intellectual Disability Research, 36, 349 –357.
- Carstairs, V. & Morris, R. (1989)
Deprivation: explaining the differences in mortality between Scotland and
England and Wales. BMJ,
299, 886
–889.
[Abstract/Free Full Text] - Cooper, S.-A. (1997) Epidemiology of
psychiatric disorders in elderly compared with younger adults with learning
disabilities. British Journal of Psychiatry,
170, 375
–380.
[Abstract/Free Full Text] - Cooper, S.-A. (2003) Classification and assessment in learning disability. Psychiatry, 2, 12 –17.
- Cooper S.-A. & Bailey N. M. (2001) Psychiatric disorders amongst adults with learning disabilities: prevalence and relationship to ability level. Irish Journal of Psychological Medicine, 18, 45 –53.
- Cooper S.-A., Melville C. A. & Morrison J.
(2004) People with intellectual disabilities. Their health
needs differ and need to be recognised and met. BMJ,
329, 414
–415.
[Free Full Text] - Corbett, J. A. (1979) Psychiatric morbidity and mental retardation. In Psychiatric Illness and Mental Handicap (eds F. E. James & R. P. Snaith), pp. 11 –25. Gaskell.
- Curtice L., Cooper S.-A., Espie, C. A., et al (2001) Implementing Partnership for Health: Piloting Health Checks for People with Learning Disabilities in Glasgow – Final Report. Greater Glasgow Primary Care NHS Trust R&D Directorate.
- Deb, S., Thomas, M. & Bright, C. (2001) Mental disorder in adults with intellectual disability. I. Prevalence of functional psychiatric disorder among a community-based population aged between 16 and 64 years. Journal of Intellectual Disability Research, 45, 495 –505.[CrossRef][Medline]
- Einfeld, S. L. & Tonge, B. J. (1999) Observations on the use of the ICD–10 guide for mental retardation. Journal of Intellectual Disability Research, 43, 408 –412.
- Farmer, R., Rohde, J. & Sacks, B. (1993) Changing Services for People with Learning Disabilities, pp. 17–30. Chapman & Hall.
- Glasgow University Affiliated Programme (2001) The C21st Health Check. Glasgow: University of Glasgow.
- Hamilton, D., Sutherland, G. & Iacano, T. (2005) Further examination of relationships between life events and psychiatric symptoms in adults with intellectual disability. Journal of Intellectual Disability Research, 49, 839 –844.[CrossRef][Medline]
- Hastings, R. P., Hatton, C. & Taylor, J. L., et al (2004) Life events and psychiatric symptoms in adults with intellectual disabilities. Journal of Intellectual Disability Research, 48, 42 –46.[CrossRef][Medline]
- Honeycutt, A. A., Grisse, S. D., Dunlap, L. J., et al (2003) Economic costs of learning disabilities, cerebral palsy, hearing loss, and vision impairment. In Using Survey Data to Study Disability: Results from the National Health Interview Survey on Disability (eds B. M. Altman, S. N. Barnett, G. Henderson, et al), pp. 207–228. Elsevier.
- King, B. H., DeAntonio, C., McCracken, J. T., et al
(1994) Psychiatric consultation in severe and profound mental
retardation. American Journal of Psychiatry,
151, 1802
–1808.
[Abstract/Free Full Text] - Linaker, O. M. & Nitter, R.(1990)
Psychopathology in institutionalised mentally retarded adults.
British Journal of Psychiatry,
156, 522
–525.
[Abstract/Free Full Text] - Lund, J. (1985) The prevalence of psychiatric disorder in mentally retarded adults. Acta Psychiatrica Scandinavica, 72, 563 –570.[Medline]
- McGrother, C., Thorp, C., Taub, N., et al (2001) Prevalence, disability and need in adults with severe learning disability.Tizard Learning Disability Review, 6, 4 –13.
- Moss, S., Prosser, H., Costello, H., et al (1998) Reliability and validity of the PAS-ADD Checklist for detecting psychiatric disorders in adults with intellectual disability. Journal of Intellectual Disability Research, 42, 173 –183.
- NHS Health Scotland (2004) Health Needs Assessment Report. People with Learning Disabilities in Scotland. NHS Health Scotland.
- Royal College of Psychiatrists (2001) DC–LD: Diagnostic Criteria for Psychiatric Disorders for Use with Adults with Learning Disabilities/Mental Retardation, (Occasional Paper OP48). Gaskell.
- Scheepers, M., Kerr, M., O’Hara, D., et al (2005) Reducing health disparity in people with intellectual disabilities: a report from the Health Issues Special Interest Research Group of the International Association for the Scientific Study of Intellectual Disabilities. Journal of Policy and Practice in Intellectual Disabilities, 2, 249 –255.[CrossRef]
- Simpson, N. J. (1999) Psychiatric Disorders in People with Learning Disabilities: Measuring Prevalence and Validating a Screening Instrument. Ph.D. Thesis, pp. 160 –161. University of Manchester.
- Singleton, N., Bumpstead, R., O’Brien, M., et al (2001) Psychiatric Morbidity Among Adults Living in Private Households, 2000. TSO (The Stationery Office).
- Smiley, E. (2005) Epidemiology of mental health
problems in adults with learning disability: an update. Advances in
Psychiatric Treatment, 11, 214
–222.
[Abstract/Free Full Text] - Sparrow, S. S., Balla, D. A. & Cicchetti, D. V. (1984) A Revision of the Vineland Social Maturity Scale by E. A. Doll. American Guidance Service.
- Sturmey, P. (1995) DSM–IIIR and persons with dual diagnosis: conceptual issues and strategies for future research. Journal of Intellectual Disability Research, 39, 357 –364.
- Sturmey, P., Newton, J. T., Cowley, A., et al
(2005) The PAS-ADD Checklist: independent
replication of its psychometric properties in a community sample.
British Journal of Psychiatry,
186, 319
–323.
[Abstract/Free Full Text] - Taylor, J. L., Hatton, C., Dixon, L., et al (2004) Screening for psychiatric symptoms: PAS-ADD Checklist norms for adults with intellectual disabilities. Journal of Intellectual Disability Research, 48, 37 –41.[CrossRef][Medline]
- World Health Organization(1968) Eighth Revision of the International Classification of Diseases: Glossary of Psychiatric Disorders. WHO.
- World Health Organization (1993) The ICD–10 Classification of Mental and Behavioural Disorders: Diagnostic Criteria for Research. WHO.
- Wright, E. C. (1982) The presentation of mental
illness in mentally retarded adults. British Journal of
Psychiatry, 141, 496
–502.
[Free Full Text]
Related articles in BJP:
- PETER TYRER
BJP 2007 190: 90.[Full Text]
This article has been cited by other articles:
 |
|
 |
|
  J. M. Jurkowski, Y. Rivera, and J. Hammel Health Perceptions of Latinos With Intellectual Disabilities: The Results of a Qualitative Pilot Study Health Promot Pract, January 1, 2009; 10(1): 144 - 155. [Abstract] [PDF]
|
|
|
|
 |
|
 P. Tyrer From the Editor's desk The British Journal of Psychiatry, January 1, 2009; 194(1): 100 - 100. [Full Text] [PDF]
|
|
|
|
 |
|
 D. Allen The relationship between challenging behaviour and mental ill-health in people with intellectual disabilities: A review of current theories and evidence J Intellect Disabil., December 1, 2008; 12(4): 267 - 294. [Abstract] [PDF]
|
|
|
|
|
|
V. A. Morgan, H. Leonard, J. Bourke, and A. Jablensky Intellectual disability co-occurring with schizophrenia and other psychiatric illness: population-based study The British Journal of Psychiatry, November 1, 2008; 193(5): 364 - 372. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Kirov, D. Gumus, W. Chen, N. Norton, L. Georgieva, M. Sari, M. C O'Donovan, F. Erdogan, M. J Owen, H.-H. Ropers, et al. Comparative genome hybridization suggests a role for NRXN1 and APBA2 in schizophrenia Hum. Mol. Genet., February 1, 2008; 17(3): 458 - 465. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Ruedrich, J. Dunn, S. Schwartz, and L. Nordgren Psychiatric Resident Education in Intellectual Disabilities: One Program's Ten Years of Experience Acad Psychiatry, December 1, 2007; 31(6): 430 - 434. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Emerson and C. Hatton Mental health of children and adolescents with intellectual disabilities in Britain The British Journal of Psychiatry, December 1, 2007; 191(6): 493 - 499. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. SMILEY, S.-A. COOPER, J. FINLAYSON, A. JACKSON, L. ALLAN, D. MANTRY, C. McGROTHER, A. McCONNACHIE, and J. MORRISON Incidence and predictors of mental ill-health in adults with intellectual disabilities: Prospective study The British Journal of Psychiatry, October 1, 2007; 191(4): 313 - 319. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. R. A S Mukherjee Prevalence of clinically diagnosed mental ill-health in adults with intellectual disabilities is around 40% Evid. Based Ment. Health, August 1, 2007; 10(3): 94 - 94. [Full Text] [PDF]
|
|
eLetters:
Read all eLetters
- Mental ill health and intellectual disabilities-Role of care programme approach
- Lakshmiprabha Ramasubramanian, et al.
- BJP Online, 1 Feb 2007 [Full text]
- Untitled
- Wael Foad
- BJP Online, 29 May 2007 [Full text]
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||