Synchrony of Change in Depression and Disability
What Next?

THE ARTICLE by Judd et al1 from the Collaborative Program on the
Psychobiology of Depression from the National Institute of Mental Health
(Bethesda, Md) confirms and extends earlier longitudinal work on the
synchrony of change in depression severity and level of psychosocial
disability.

These earlier naturalistic studies2-4 found that disability was reduced
among patients in primary care whose depressive and anxiety disorders
improved, while, in contrast, patients whose psychological illness ran a
chronic course maintained elevated disability levels 1 to 3 years later.

Judd et al now show that the synchrony of change in depression severity and
level of disability remains at the within-subject level over 10 years on
average.

Increments in depressive symptom severity were associated with increments
in disability, and reductions in depressive symptom severity were
associated with reductions in disability.

What is new and exciting in their work is the combination of monthly
assessments of symptoms and psychosocial functioning over an extended
period with the application of recently developed advanced statistical
methods, which comprise the so-called random regression model.

MEASUREMENT OF DISABILITY

Notwithstanding these innovative features, there may be some problems with
their measurement of disability.

The assessments of psychosocial functioning apparently counted only
impairments in functioning that were attributable to depressive symptoms.

While this does not imply a rating of impairment in those with depressive
illness, it seems to imply a rating of no impairment in those without
depressive symptoms.

The rating of only depression-associated impairment may have produced
spurious association.

This risk may have been further enhanced by the use of the same interviewer
for rating depression and disability and the exclusive reliance on
interviewers at the expense of other, more objective indicators of
disability.

Because other studies2, 3 suggest that similar, albeit less strong,
associations would have been observed if disability was measured completely
independent of psychological state, we do not think that their procedures
have seriously biased their findings.

It would be reassuring, however, if future disability assessments included
independent sources (family members or employers) or performance-based data
(absenteeism or productivity).

ADVANCES IN THE FIELD

Considerable progress has been made in understanding the relationship
between depression and disability since the introduction of the
International Classification of Impairments, Disabilities and Handicaps5 in
1980 and the landmark Medical Outcome Study by Wells et al6 in 1989.

The triad of impairment, disability, and handicap provided the framework
for expanding disease concepts to include their effect on physical and
psychosocial functioning.

The Medical Outcome Study found that people with depression showed similar
or poorer functioning than patients with chronic medical diseases, except
in cases of patients with advanced coronary heart disease.

The major findings of subsequent studies include the following:

1. The association of major and minor depression and depressive symptoms
with disability is common in all cultures.7 The depression-disability
relationship was not limited to the United States and European countries
with highly developed economies and social welfare systems, but was also
found in Asian, South American, and African countries.

2. Depression is a risk factor for onset of both physical and psychosocial
disability.8-12 There are now at least 5 prospective studies reporting that
preexisting depression is a risk factor for onset of disability.8-12

3. Effective treatment of depression improves functional outcomes.
Five13-17 of 618 randomized, controlled trials that included good measures
of disability have reported favorable disability outcomes in the
experimental treatment group relative to usual care.

There is also some evidence that a comprehensive depression training
program for primary care physicians that included substantial hands-on
learning improved disability outcomes among patients with depression of
recent onset.19, 20

4. While these studies collectively suggest a causal effect of depression
on psychosocial disability, part of the association may be due to effects
of disability on depression.

In older populations with high prevalences of chronic medical disease,
limitations in activities of daily living have been found to predict onset
and worsening of depressive illness.21-23

Consequently, the association between depression and disability might be
due to bidirectional effects among depression, physical limitations, and
psychosocial disability, in particular in older people and younger medical
patients.

THE FUTURE OF RESEARCH

What is the future of research in the field now that it has progressed so
far? What research questions need to be addressed? What steps need to be
taken to improve functional outcomes of psychological illness on a
population basis?

One promising direction is the conceptualization of disability in terms of
social role performance.24

We lack insight into the development and course of the behavioral effects
of depression on disability in social role performance.

Is there a hierarchical structure in role disability?

Work on severe mental illness suggests that social activities and family
roles are the first to manifest disability, followed by the work role and,
finally, the self-care role.24

Do loss and recovery of social role performance among persons with
depression follow a similar pattern?

We know little about the lag times between onset and remission of
psychological impairments and associated effects on social role functioning.

The evidence of disability associated with medical disease as a risk factor
for depression elicits intriguing questions on bidirectional effects
between depression and disability.

To what extent does disability, triggered by medical disease or social
stress, propel the onset and maintenance of depression?

Further research on the complex, possibly multidirectional effects among
physical disease, depression, and physical and social role disability is
needed.

Modifying influences is another concern.

The association between psychological illness and psychosocial dysfunction
is strong, but not absolute.

Some people with depression function rather well.

The question here is what environmental and psychological factors dampen or
enhance the effect of psychopathology on disability.

Such knowledge may enhance the effectiveness of treatments for depression,
as well as provide possible benefits for disability outcomes.

PUBLIC HEALTH AND THE ORGANIZATION OF HEALTH CARE

Although understanding of the causal relationships between depression and
disability is far from perfect, there is now substantial evidence that
improved treatment of depression reduces social role disability.

In 1992, the finding of synchrony of change led us to conclude that "At
present, there is an urgent need for randomized controlled trials of
treatment of depressive illness . . . to assess effects on functional
disability. . . . If such effects were reliably observed . . . current
efforts to increase the recognition and effective management of depression
by health care providers would be markedly advanced."2

Now, at the turn of the century, these trials have been performed.

The public health challenge now is to organize health care systems so that
they are capable of providing effective treatment to all people with
depressive illness.

Effective treatments are not sufficient; we also need effective health care
systems capable of disseminating those treatments to entire populations.25

It is heartening to see the progress that has been made in the field in the
1990s, from epidemiological research demonstrating the
depression-disability association to randomized controlled trials of
interventions that improved both depression and disability.26

The public health challenge for the next decade is to develop dissemination
strategies that ensure effective treatment of depressive illness on a
population basis.

Beyond that, there remains an urgent need for greater understanding of the
mechanisms and effective management of disability due to psychological
illness than currently exists.

Although rapid progress has been made, depression remains one of the
leading causes of disability throughout the world.27


Author/Article Information

Johan Ormel, PhD
Department of Psychiatry
University of Groningen
The Netherlands
and
Institute of Psychiatry
Kings College
London, England

Michael Von Korff, ScD
Seattle, Washington, USA

Archives Of General Psychiatry
Vol. 57 No. 4, April 2000
http://archpsyc.ama-assn.org/issues/v57n4/full/ycm9432.html
2000 American Medical Association. All rights reserved.

janet paterson
53 now / 41 dx / 37 onset
a new voice: http://www.geocities.com/janet313/
613 256 8340 PO Box 171 Almonte Ontario Canada K0A 1A0