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Depression & Chronic Pain
Last edited |
10/25/2008
Surprisingly, few studies have attempted
to determine if a comorbid medical condition in individuals with chronic painful
physical disease increased the likelihood of having a major depressive disorder
Some studies have reported associations
between depression and a number of long-term medical painful conditions including pain
syndrome:
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An epidemiological study performed in the UK reported a
prevalence of 16.9% of participants with chronic widespread pain had a
psychiatric diagnosis (13).
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A seven-year longitudinal study reported that the
presence of multiple physical symptoms is predictive of a new onset of
depression (8) and conversely, depressed subjects are three to seven times more
likely to develop multiple physical symptoms than are non-depressed subjects.
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More recently, a one year longitudinal study reported that non-depressed
subjects with a long-term medical condition (migraine headaches, sinusitis or
back problems) are twice as likely to develop a major depression within the next
year than are other individuals (11).
Few studies have attempted to determine the role of obesity, a factor
found to be associated with increased pain severity in studies on pain (14,15)
and with increased likelihood of major depressive disorders in studies on
depression (16, 17), in the association between pain and depression.
Research In this study, we explored further
the relationship of chronic painful physical condition to depression in a
large community sample composed of 18,980 Europeans aged 15 years and older.
We wanted to find:
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the prevalences of pain, depressive
symptoms, and major depression in this representative sample;
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the degree of association between chronic
painful physical condition and depressive symptomatology and major depressive
disorder diagnosis;
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other factors such as a comorbid
non-painful medical condition modifying the association between pain and
depression;
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if pain symptoms are more common than
classic vegetative symptoms in a community based sample of subjects with major
depressive disorder diagnosis.
Methods
The participants in the five countries were
interviewed by telephone between 1994 and 1999 with the broader purpose of
investigating sleep habits, sleep-related symptoms and psychiatric and sleep
disorder diagnoses according to DSM-IV.
The target population was all
non-institutionalized residents ages 15 years or over living in the United
Kingdom, Germany, Italy, Portugal.
These five countries totaled approximately
206 millions inhabitants.
A two-stage sampling design, was used for all five
countries using the geographical distribution in the
first stage and the Kish selection method (18) in the
second stage.
The Kish method is based on eight selection tables. It
maintains the representation of the sample in terms of age
and gender and avoids bias related to non-coverage error.
The
participation rate was 79.6% (4,972 of 6,249 eligible individuals) in the UK;
68.1% (4,115 of 6,047 eligible individuals) in Germany; 89.4% (3,970 of 4,442
eligible individuals) in Italy; 83% (1,858 of 2,234 eligible subjects) in
Portugal; and 87.5% (4,065 of 4,648 eligible individuals) in Spain.
Altogether, 18,980 subjects participated in the study.
The
overall participation rate was 80.4%.
Results
The sample included 18,980 subjects between 15 and 100 years
old:
Limitations of the study
This was designed primarily as a study
to address sleep and mental disorders in the general population and the
questionnaire did not include extensive questions about pain and their sites.
Therefore, it was not possible to distinguish between the different clinical
forms of pain with great specificity.
Second,
the data collected on pain and non-painful medical conditions relied on
self-reporting.
However, since pain involves mainly a subjective perception and experience,
self-reports are commonly considered accurate for the report of pain.
Studies
that have examined the concordance between subjective reports of pain and
external measures of pain have found good agreement between the two (27).
Furthermore, a physician or another health specialist had already diagnosed
non-painful medical conditions reported in this study.
Prevalence of DSM-IV depressive disorders
diagnoses
We found a prevalence of 4% of major
depressive disorders in this European sample, which is close to the one-month
prevalence of 4.9% reported in the National Comorbidity Survey (NCS) (2).
The
main differences between this study and the ECA (1) and NCS studies are
numerous:
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First, the age range is broader in this sample (15 to 100 years old)
than in the NCS study (15 to 54 years old).
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Second, the time frame is also
different (point prevalence in this study, 1-month, 6-month, 1-year or
lifetime prevalence in the NCS and ECA studies), and
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Third, in this study, a
differential diagnosis procedure was applied to all the subjects with a major
depressive episode.
The pain-depression association
Among the 4% of subjects in the sample
with a major depressive disorder diagnosis, over 40% also had a chronic
painful physical condition.
A third of subjects with a major depressive
disorder diagnosis had a non-painful medical condition.
Therefore, only 38.4% of subjects with a major depressive disorder had neither
a chronic painful physical condition nor a non-painful medical condition;
approximately 15% had both.
In
subjects with a major depression diagnosis, the odds of having a chronic
painful physical condition were greater than for depressive symptoms ranging
from 2.0 to 5.0 (crude odds ratios).
Conversely, among subjects with a chronic painful condition, the highest odds
of having a depressive disorder diagnosis were found in subjects who reported
backache or headaches.
These results confirm those in other clinical studies
that examined the prevalence of a depressive disorder diagnosis in patients
with low back pain or headaches (37-40).
Interestingly, 24-hour presence of
pain made an independent contribution to the presence of a major depressive
disorder diagnosis, indicating that continuous pain by itself increases the
likelihood of having a major depressive disorder diagnosis.
Furthermore, when
controlling for the presence of a non-painful medical condition, a chronic
painful physical condition remains an important factor related to the presence
of a major depressive disorder.
Both, the influence of 24-hour pain and comorbid chronic painful physical condition and non-painful medical condition
were never investigated in the general population prior this study.
Other results are noteworthy:
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We found in
that study that shift working was a predictive factor for major depressive
disorders as were unemployment and being homemaker.
Previous epidemiological
studies on major depressive disorders did not pay attention to separate working
individuals according to their work schedule (1-5).
However, some studies on
shift workers have reported high rates of major depressive disorders in this
population (41,42).
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We also investigated the influence of obesity on the
association pain and major depressive disorders because obesity has been
demonstrate to be related to the severity of the pain on one hand (14,15) and to
the presence of major depressive disorder on the other hand (16,17).
Interestingly, in bivariate analyses, these two associations were observed;
i.e., obese individuals are more likely to report a chronic painful condition
and they have a higher prevalence of major depressive disorders than the normal
weighted individuals.
However, when introduced into a multivariate model, the
association obesity and major depressive disorder disappeared.
Instead, we found
that being over-weighted was a protective factor for major depressive disorder.
Should depression be assessed differently in
subjects with chronic pain?
The
pain-depression interaction is not yet fully understood.
Some
argue that chronic pain should be viewed as a potent physical and psychological
stressor that may influence mood:
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Thus, pain can be viewed as a potential trigger of the depressive illness.
Some longitudinal studies partly support that hypothesis (8-12).
The relationship, however, is far more complex: if pain precedes the depressive
illness in as many as 40% of cases, the reverse is also true: depressive illness
often precedes physical pain (7,8,10,12).
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Our
data are cross-sectional; therefore, it offers limited information about the
course of pain and depression.
We found, however, that depressed mood is significantly longer - about six
months - in subjects who have reported a chronic painful physical condition.
Therefore, pain could also contribute to the prolongation of a depressive
episode.
This result has also been reported in clinical studies (44).
On
the other hand, others argue that depression should be assessed differently in
subjects with physical pain or, at least, that special attention should be
brought to somatic symptoms of depression, that are also often associated with
physical pain and can in fact be attributable to the painful physical condition
rather than to depression (45-47).
Therefore, there is a question as the extent to which painful physical condition
can induces a false-positive diagnosis of a major depressive disorder.
In this study, we found that changes in
appetite or weight, fatigue, insomnia/hypersomnia and feelings of worthlessness
or guilt were frequently associated with pain alone.
About 88% of subjects with a depressive disorder diagnosis reported somatic
depressive symptoms: fatigue, sleep and appetite disturbances. If we
exclude subjects who reported both a chronic painful physical condition and
somatic symptoms of depression and who did not have sufficient depressive
symptoms to fulfill the criteria of a major depressive episode, the prevalence
of a depressive disorder diagnosis drops to 3.4%. Therefore, about 15% of
depressive disorder diagnoses would be discarded.
There is no clear consensus on how to manage depressive somatic symptoms in the
context of painful physical conditions:
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Some
argue that the overlap between pain and depressive symptoms may even compromise
the validity of diagnostic questionnaires in that specific population (48-50).
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In
this regard, Endicott (51) has recommended that alternative diagnostic criteria
be used e.g., using non-somatic substitute symptoms to make the diagnosis of
major depression.
In
summary, this study clearly shows the importance of chronic painful physical
condition in major depressive disorders.
Pain
is a common symptom that remains strongly associated with major depressive
disorder even when controlling for the presence of non-painful medical
conditions.
Furthermore, the co-occurrence of chronic painful physical condition and
non-painful medical condition increased the likelihood of having a major
depressive disorder.
Further studies on the relationship of pain to major depressive disorders appear
warranted.
Content of this page
is extracted from
Ohayon MM, Schatzberg AF. Using chronic pain to predict depressive morbidity in the
general population. Arch Gen Psychiatry. 2003
Jan;60(1):39-47.
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