JRSM >
Volume 97, Number 8 >
Pp. 375-379
Academic Clinical Psychiatry, Division of Genomic Medicine, University of Sheffield, The Longley Centre, Norwood Grange Drive, Sheffield S5 7JT, UK
Correspondence to: Dr Sean Spence E-mail: s.a.spence{at}sheffield.ac.uk
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 TOP SUMMARY INTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
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| INTRODUCTION |
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Those who are homeless and also mentally ill are among the most marginalized members of society. Indeed, one of the stated aims of the UK Government's National Service Framework for Mental Health5 and the Social Exclusion Unit6 is to reduce such exclusion. The success of such enterprises may, at least partly, depend upon the capacity of affected individuals to recover and reintegrate into their communities. With this in mind, we set out to examine the evidence that cognitive function might be impaired in those who are homeless. Here, 'cognitive function' comprises those neuropsychological processes supporting mental activity—e.g. memory and attention—and so-called 'executive' functions (the planning and control of behaviour). Given the pivotal role of executive functions in the control of voluntary behaviours,7 we posited that these might be dysfunctional in those who are unable to find or retain permanent accommodation.
The present study examines evidence for an association between homelessness and cognitive deficit in adults. It should be noted at the outset that no studies have been formally designed to investigate cognitive impairment as a risk factor for becoming homeless (according to our methodology, described below) and little work has been done on the impact of homelessness upon cognition per se (see below). Hence, for the time being the question of causality cannot be resolved.
| METHODS |
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Study selection and data synthesis
On the basis of pilot searches we expected the published work to be scarce,
so our inclusion criteria were liberal. All studies published in journals were
selected that involved homelessness and cognitive function, irrespective of
hypotheses tested. Our central research question required the reporting of
cognitive test data; hence, in the final review we included only those studies
where cognitive assessments had been performed among a cohort of individuals
(at least 3) in the context of homelessness. Since statistical combination of
studies should not form a prominent component in the synthesis of
observational
studies,8 no attempt
was made at meta-analysis of the data found in the included studies.
| RESULTS |
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Demographic factors
Definitions of homelessness varied across studies, incorporating those who
were literally
'roofless'24
and those for whom accommodation was inherently unreliable or temporary (e.g.
in the hostels of
London).22,23
Numerically, most studies concerned hostel residents and the majority of those
studied were male (81% of adults, where gender is clearly reported). Ethnicity
is not always reported, but where it is, mostly in USA and UK studies, there
is an over-representation of 'visible'
minorities.12,13,16,18–20,22
Sample heterogeneity
In the context of the total number of homeless worldwide, the number of
homeless adults studied from a cognitive perspective seems rather
small—around 3300 for whom data are fully reported. Also, studies have
varied in their orientation towards the mentally ill. While some have
attempted to exclude those with psychiatric
disorders,17,19
others have specifically targeted this
group.18 Similarly,
some workers have attempted to exclude those abusing alcohol or illicit
substances17 while
most have included them. Given the high prevalence of psychiatric disorders,
including the addictions, among the
homeless,29 it is
pragmatic to include those so affected, since otherwise the surveyed sample is
unlikely to represent real-world circumstances (at least in the urban West).
Many studies reviewed have recorded high rates of
depression,11,14,18,20,22–24,27
schizophrenia,11–13,18,21–24
alcohol
dependence12,14–15,20,23–24
and head injury23
among the homeless. Hence, there is considerable psychopathology but also
heterogeneity among the samples assayed. Few researchers have incorporated
control groups or comparison data. These features may be related to the
sampling methods applied, which have generally comprised cross-sectional
surveys of a given facility (e.g. a hostel or clinic), with only a minority of
groups attempting an epidemiological
approach.11,13,24
Global cognitive impairment
Notwithstanding the caveats noted above, there is the impression of greater
comparability across studies in terms of cognitive assessment. Of the 18
studies assayed, 10 (reported in nine papers) have used the same screening
tool—the Mini Mental State Examination
(MMSE).11–13,20–24,26
Although an insensitive indicator of cognitive impairment, this provides a
brief easy-to-administer test battery that can be incorporated into a clinical
assessment and possesses high inter-rater reliability. It is not so useful for
the detection of focal cognitive deficits (e.g. aphasia) and is
insensitive to frontal lobe
disorders.30 Among
adults living in the community, the proportion expected to exhibit deficits on
the MMSE is about 2–3%, whereas most studies of the homeless have shown
much higher
rates,11,13,20,21,23,24,26
reaching
30–40%.20,21
Only 2 of these 10 studies incorporate comparative
data.12,13
Both are American and utilize data from the Epidemiological Catchment Area
Survey; both report increased rates of cognitive impairment among the
homeless. In the Koegel
study,13 the
comparison data relate to domiciled 'alcoholics', the latter
exhibiting less cognitive impairment than an index group of homeless
'alcoholics'. This is the most informative controlled study
available.
To summarize the MMSE data, in most studies of homeless adults those sampled exhibit high rates of generalized cognitive impairment.
Focal cognitive impairment
On the question of focal cognitive impairment, notably few studies
have employed neuropsychological tests that might be expected to detect
frontal lobe (executive) impairment. The latter would include the Wisconsin
Card Sort Test,18
the Trails B20 and
the Stroop.15 Such
tasks require the subject to apply new strategies in adapting to test
conditions,18 and
to inhibit inappropriate responses to test
stimuli.15,18,20
They are quintessentially tests of 'higher' brain
function.30 Of the
three studies incorporating these instruments, two have pointed to substantial
deficits among the
homeless,18,20
although neither included controls. The third study, though detecting a
decrement in performance, found a similar level of impairment among domiciled
(mentally ill)
controls.15 Indeed,
the authors even suggested that their homeless (mentally ill) sample might be
superior to the domiciled in certain cognitive domains—hence their
ability to survive in a hostile environment. It may be relevant that this
paper reports a study of
'veterans',15
who at one time would have been pronounced fit for armed service; presumably,
therefore, their cognitive function had been good before they became
homeless.
Studies of IQ
Studies reporting actual or estimated numerical values for adult
intelligence14,15,17,18,31
found IQ in the homeless to be in the low average to average range.
Two studies16,22 specifically compared measures of premorbid intelligence and current intelligence. Both showed a significant decline in intelligence in those individuals with mental illness (Adams et al.22 from average to borderline; Bremner et al.16 from average to low average). Bremner and colleagues16 showed a drop in those without a diagnosis, in those with alcohol dependence and concurrent drinking, and in those with 'other diagnoses' (e.g. depression, anxiety). In the same study, IQ drop, but not current IQ, correlated with duration of rooflessness. In the Adams study,22 individuals with psychosis had suffered a greater intellectual decline from their premorbid levels of function than those without psychosis. No decline was evident in the latter group.22
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There is, of course, a question as to whether such cognitive impairment is in any way specific to the homeless or whether it is similarly prevalent among other at-risk groups (e.g. people living in poverty). With the small number of studies available for review, it would be premature to draw any firm conclusions. Indeed, while homeless people are likely to experience adverse circumstances, there is not necessarily any a priori reason why they should exhibit a pattern of cognitive deficit distinct from the poor or otherwise disadvantaged, and perhaps this does not matter anyway. The medical questions pertinent to the homeless are: to what extent is cognitive/brain impairment present; what can be done to reverse/ameliorate it; and how will persistent deficits impact upon social function/reintegration? These would seem fitting questions also for medical research, yet they seem to have attracted little attention. To put things in perspective: schizophrenia is a severe mental disorder affecting approximately 1 in 100 adults worldwide,32 yet studies of cognitive dysfunction in this disorder have reported on more than 7000 patients (according to very strict defining criteria).33 The homeless may comprise as many of the world's population,2 yet their cognitive function has been reported in a little over 3000 adults (and these ascertained by use of widely variable inclusion criteria). Given the number of homeless adults living in the world, it is surprising that so few studies have examined their cognition.
In the clinic or casualty department, the presence of global cognitive impairment might be expected to impact upon the retention of new information. Hence, it may make little sense to discharge a homeless man with alcohol problems from the casualty department, expecting him to attend an alcohol service the next morning, without providing at least some written information or ensuring some means of outreach follow-up. Similarly, to discharge the homeless person with schizophrenia from hospital, in the hope that she will find and attend the housing department of the local authority, may be overoptimistic. In our own clinical practice with the roofless we have encountered people with schizophrenia who have been left untreated for a decade,34 often because they do not adhere to the outpatient model of psychiatric services.
The extent of executive (global) cognitive impairment in homeless adults requires further elucidation. There are only three studies pertaining to this important question.15,18,20 If people are to change their circumstances, to learn new skills and to break destructive patterns of behaviour then it is the executive system which is particularly implicated in such cognitive flexibility.7,35 The MMSE is not the best way to assess executive function and may accrue type II errors (false negatives).20 There is a need for studies that utilize specific probes of executive function—e.g. the Trails B, Stroop and Wisconsin Card Sort Test. When such tests are applied, then the evidence suggests that many homeless adults are executively impaired (80% in the Gonzalez study20).
We cannot comment on whether cognitive dysfunction predisposes people to homelessness, for no prospective studies have addressed this question. Similarly, evidence of a direct impact of homelessness upon cognition is very limited. The studies that we have identified among the homeless mentally ill do, however, suggest that extent of cognitive decline is related to indices of homelessness.22,23 Similarly, and despite its considerable face validity, whether or not cognition impacts upon the ability to resettle can only be inferred indirectly from cross-sectional data.21
What is to be done? Our findings suggest that it may be prudent to assess cognition when encountering patients who are homeless, especially if they are also mentally ill. While the busy clinical setting may constrain the extent of cognitive assessment, the MMSE and a test of verbal fluency might be performed within 5 minutes and reveal signs of dysfunction.30 In psychiatric services that assess homeless people, access to neuropsychological assessment seems essential. More than the symptoms of psychosis, it is the extent of cognitive dysfunction that predicts social outcome among those with schizophrenia36 and there is no reason to assume that this is any less true for patients who are homeless.
| Acknowledgments |
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