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PSYCHIATRIC MORBIDITY IN ADULTS WITH DOWN'S SYNDROME
Vee P Prasher
There is an increased prevalence of psychiatric disorders in
people with intellectual disabilities (Deb et al, 2001). However,
certain types of disorder are more common amongst people with
Down's syndrome, compared to other adults with intellectual disabilities:
Alzheimer's, dementia, depression, and obsessive-compulsive disorder.
This article reviews the current literature regarding the main
types of mental illness that people with Down's syndrome may experience
during their lifespan. Whilst particular attention is given to
the association of Alzheimer's dementia with Down's Syndrome,
other mental disorders are also discussed (including schizophrenia
and anxiety disorders). The differences in the presentations of
such disorders in people with intellectual disability are discussed,
together with the challenges that face clinicians in detecting
these illnesses. This article is particularly helpful for medical
students, trainee psychiatrists, and general practitioners wanting
an overview of the association between mental illness and Down's
Sydrome.
Prevalence of psychiatric disorders
An increase in the prevalence of psychiatric disorders in people
with intellectual disability has been reported (Deb et al., 2001).
Prevalence rates have been consistently demonstrated to be higher
in adults with Down's syndrome than in the general population,
with overall rates similar to those for learning-disabled adults
who do not have Down's syndrome. Although the overall rates are
similar, there is a difference in the type of disorders present:
DAT, obsessive-compulsive disorders and depression are more common
among people with Down's syndrome (see
Figure 1).
Specific types of psychiatric disorder
Dementia
The first reported association between Down's syndrome and DAT
was made by Fraser and Mitchell in 1876. Commenting on people
with Down's syndrome, they wrote: 'in not a few instances, however,
death was attributed to nothing more than general decay - a sort
of precipitated senility'. The association has been well established
since then.
Aetiology: the high risk of DAT in adults with Down's
syndrome is principally due to the triplication and over-expression
of the gene for amyloid precursor protein (APP) located on chromosome
21. Evidence increasingly suggests that the presence of one or
more copies of APOE E4, as in the general population, increases
the risk for DAT in the Down's syndrome population. The presence
of the APOE E2 allele possibly increases longevity and reduces
the risk. A family history of dementia, sex differences and the
effects of oestrogen in Down's syndrome are yet to be fully investigated.
Prevalence: the prevalence rate of dementia of all types
in the general population varies from 0.6% to 21%, depending on
the age of the sample studied. Identification of DAT in the Down's
syndrome population has proved to be difficult, leading to a wider
variation in rates of 15-45%. The mean age of onset of DAT is
50-55 years, with onset as young as 30 years. The mean duration
of DAT is approximately 6 years but can range from a few months
to 21 years (Prasher and Krishnan, 1993).
Psychopathology: signs and symptoms of DAT in adults with
Down's syndrome may be difficult to diagnose because of the underlying
mental impairment. Dalton and Crapper-McLachlan (1986) reviewed
35 case reports of people with Down's syndrome who had received
a clinical description relating to the development of DAT. The
most frequently occurring symptom/sign was the presence of epilepsy
(88% of cases), followed by focal neurological signs (46%) and
personality change (46%). See
Figure 2 for other symptoms/signs, in order of frequency.
Lai and Williams (1989) described three phases of DAT:
- In the initial phase memory impairment, temporal disorientation,
and reduced verbal output were evident in higher-functioning
individuals with Down's syndrome. For those with more severe
learning disability, the first indications of dementia were
apathy, inattention and reduced social interactions.
- In the second phase, there was loss of self-help skills such
as dressing, toileting and use of food utensils. The gait was
often slowed and shuffling.
- In the final phase the patients were non-ambulatory and bed-ridden,
and often assumed flexed postures. Sphincter incontinence was
present and pathological reflexes such as sucking, palmar grasp,
palmomental and glabellar reflexes were prevalent. Parkinsonism
developed in 20% of cases. Seizures developed in 41 of the 49
demented patients, and occurred in all 23 who died. Ten patients
had the flexed posture, bradykinesia, masked face and cogwheel
rigidity of Parkinsonism.
Diagnosis: unlike in the general population, in people
with intellectual disabilities there are no approved systematic,
acceptable, standardized forms of assessment. Quantitative measures
of cognitive functions such as memory and attention span have
not been reliably demonstrated. Measurements of other intellectual
functions (e.g. speech, comprehension and visuo-spatial function)
remain elusive. However, a number of assessment measures have
been proposed to detect dementia in people with Down's syndrome
(see
Figure 3).
Management: the management of dementia in Down's syndrome
is similar to that for the general population. Once the diagnosis
has been made there are four main areas of management.
Treat the underlying disease process - anticholinesterase
(AChE) inhibitors (donepezil, rivastigmine, galantamine) have
now been established as drugs that can slow down the rate of deterioration
of DAT in both the general population and the Down's syndrome
population.
Treat associated symptoms - many of the clinical symptoms
of dementia can be treated. Seizures should be treated with standard
anticonvulsant therapy; insomnia with mild night sedation; aggression,
irritability and psychotic features with neuroleptic medication;
and low mood with antidepressants.
Psychological intervention - although not fully researched
in the field of learning disability there is growing evidence
that psychological/behavioural intervention can benefit adults
with dementia in the general population (Hollins and Sinason,
2000) (see also Banks 2003, pp.62-65). Reminiscence therapy, reality-orientation
therapy and behavioural therapy (including occupational therapy)
can maintain current skills and reduce deterioration.
Support for carers - most Down's syndrome adults with dementia
reside in the community, either with family carers or with paid
carers. Education, increased community nursing support and greater
involvement of the primary health services can all enable people
with dementia to be managed for longer in their homes and delay
necessary admission to a nursing home. Carers can also receive
considerable support from charities such as the Down's Syndrome
Association and the Alzheimer's Society (see
Figure 4 for contact details).
Affective disorders
In the general population, the prevalence of affective disorders
varies depending on the diagnostic criteria used, but the rate
of depression is in the order of 2-10%. Among people with intellectual
disabilities the prevalence of depression is approximately 1-3.5%.
There have been few epidemiological studies of depression in people
with Down's syndrome. Myers and Pueschel (1991), in their study
of 497 people with Down's syndrome, found depression in 10 adults
(2%). Prasher (1995), in a study of 201 adults with Down's syndrome,
found a point prevalence of 5.0%.
Presentation: the presentation of depression in adults
with Down's syndrome differs from that in the general population.
Cognitive features (e.g. disturbance of memory, loss of concentration,
suicidal ideation) may not be apparent. Biological features (psychomotor
retardation, disturbed sleep, loss of appetite, loss of weight)
may be more significant. Decline in adaptive skills (e.g. dressing,
washing, feeding) is significantly associated with depression.
Management: the assessment and treatment of affective
disorders should follow the same clinical guidelines as for the
general population. Drug treatments (neuroleptic medication, antidepressants,
mood stabilizers), psychotherapy and electroconvulsive therapy
all have a role to play and have been reported to be of benefit
in the treatment of depressive episodes in adults with Down's
syndrome. Further research investigating the value of diagnostic
instruments and rating scales, outcome post-illness and response
to treatment is required.
Schizophrenia
Prevalence rates of schizophrenia of around 3-6% have been demonstrated
in people with intellectual disabilities (compared with 0.5-0.8%
for the general population). Although case reports of schizophrenia
in people with Down's syndrome have been described there has been
little investigation of the prevalence and/or possible association
between schizophrenia and Down's syndrome.
There are considerable difficulties in diagnosing an episode of
schizophrenia in adults with Down's syndrome: eliciting abnormalities
of thought and of psychotic experiences in people with severe
intellectual impairment is difficult (Prasher 2003, p.10), and
so standard diagnostic criteria may not be applicable. To date
there is no strong evidence to suggest that people with Down's
syndrome are particularly susceptible to schizophrenia. However,
considerable methodological difficulties still need to be overcome
before any firm conclusions can be drawn.
Obsessive-compulsive disorder
The prevalence of obsessive-compulsive disorder (OCD) is reported
to be 1.65-2.5% in the general population. Myers and Pueschel
(1991) found that 4 (1.7%) of 236 Down's syndrome individuals
had OCD, and Prasher (1995) found OCD in 9 (4.5%) of 201 subjects.
Ordering is the most common type of action/obsession, along with
ritualistic touching and cleaning.
It can be difficult to distinguish compulsive disorders from stereotypies
in people with intellectual disabilities, and this must be borne
in mind before a diagnosis of OCD is made. Obsessional repetitive
thoughts can occur in people with Down's syndrome but may be difficult
to diagnose. Obsessive-compulsive acts are probably more likely
to be detected.
Phobias/anxiety
Studies in the intellectual disability population as a whole have
reported increased rates of anxiety disorders. However, anxiety-related
disorders appear to be uncommon in the Down's syndrome population.
Lund (1988) found neurotic traits in 25 (57%) of 44 adults but,
using diagnostic criteria, none was diagnosed as suffering from
a neurosis. Myers and Pueschel (1991) found that 5 (1.0%) of 497
people with Down's syndrome had a phobia disorder. Further research
in this area is required.
Other psychiatric disorders
Psychiatric disorders found in the general population, such as
somatoform disorders, drug abuse and personality disorders, are
also found in people with Down's syndrome. However, limited evidence
suggests that they do not have an increased susceptibility to
developing these disorders. Case reports of rarer disorders have
been described, including paraphilias, Tourette syndrome and eating
disorders.
Conclusion
Overall, the prevalence rates of psychiatric disorders in adults
with Down's syndrome are similar to rates in people with non-Down's
syndrome intellectual disability, but are increased compared with
the general population. DAT and possibly depression and OCD are
particularly associated with Down's syndrome. There is strong
evidence for a genetic predisposition to developing DAT, although
not all adults with Down's syndrome will do so, and there have
been several reports of adults surviving into the seventh decade
of life. The diagnosis and subsequent treatment of any given disorder
should follow guidelines used in the general population. Assessment
tools and treatment regimens may need to be modified but with
careful and detailed psychiatric evaluation virtually all disorders
can be detected. It is important that all psychiatrists are aware
of the increased psychiatric morbidity in adults with Down's syndrome.
REFERENCES
Banks R. Psychological Treatments for People with Learning Disabilities.
Psychiatry 2003; 2(9): 62-65.
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disability. I: Prevalence of functional psychiatric illness among
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Fraser J, Mitchell A. Kalmuc idiocy: report of a case with autopsy
with notes on 62 cases. J Ment Sci 1876; 22: 161.
Hollins S, Sinason V. Psychotherapy, learning disability and trauma:
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Lai F, Williams R S. A prospective study of Alzheimer disease
in Down syndrome. Arch Neurol 1989; 46: 849-53.
Lund J. Psychiatric aspects of Down's syndrome. Acta Psychiatr
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Prasher V P. Epidemiology of Learning Disability. Psychiatry 2003;
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Prasher V P, Krishnan V H R. Age of onset and duration of dementia
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Prasher V P. Prevalence of psychiatric disorders in adults with
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FURTHER READING
Berg J M, Karlinsky H, Holland A J. Alzheimer disease, Down syndrome,
and their relationship. Oxford: Oxford University Press, 1993.
(Textbook which reviews all aspects of Alzheimer's disease
in Down's syndrome.)
Pueschel S M, Pueschel J K. Biomedical Concerns in Persons with
Down Syndrome. Baltimore, MD: Paul H Brookes, 1992.
(Detailed textbook which highlights important physical and
psychiatric conditions associated with the Down's syndrome population).
| First published in Psychiatry,
Volume 2:8, August 2003 and reprinted with the kind permission
of The Medicine Publishing Company. |
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