Mood disorder with Depressive
Features
A mood disorder secondary to a general medical
condition with depressive features is characterized by a prominent and
persist-ent depressed mood or loss of interest, and by the presence of
evi-dence, from the history, physical examination or laboratory tests, of a
general medical condition capable of causing such a distur-bance. Although
other depressive symptoms (e.g., lack of energy, sleep disturbance, appetite
change or psychomotor change) may be present, they are not necessary for the
diagnosis.
The overwhelming majority of cases of depression
occur as part of one of the primary mood disorders, including major depres-sive
disorder, dysthymic disorder, bipolar disorder, cyclothymic disorder, or
premenstrual dysphoric disorder, all of which are covered elsewhere in this
text. The various secondary causes of depression are listed in Table 33.3.
In utilizing Table 33.3, the first question to ask
is whether the depression could be secondary
to precipitants. Of the vari-ous possible precipitants, substances of abuse
(e.g., as seen in alcoholism or during stimulant withdrawal) are very common
causes. Medi-cations are particularly important, however it must be borne in
mind that most patients are able to take the medications listed in Table 33.3
without untoward effect: consequently, before ascrib-ing a depression to any
medication it is critical to demonstratethat the depression did not begin
before the medication was be-gun and, ideally, to demonstrate that the
depression resolved af-ter the medication was discontinued. Anticholinergic
withdrawal may occur within days after abrupt discontinuation of highly
anticholinergic medications, such as benztropine or certain tri-cyclic
antidepressants, and is characterized by depressed mood, malaise, insomnia and
gastrointestinal symptoms such as nausea, vomiting, abdominal cramping and
diarrhea. Poststroke depres-sion is not uncommon, and may be more likely when
the anterior portion of the left frontal lobe is involved; although spontaneous
remission within a year is the rule, depressive symptoms, in the meantime, may
be quite severe. Both head trauma and whiplash injuries may be followed by
depressive symptoms in close to half of all cases.
Depression may occur secondary to diseases with dis-tinctive features, and keeping such
features in mind whenever evaluating
depressed patients will lead to a gratifying number of diagnostic “pick-ups”.
These features are noted in Table 33.3, and are for the most part
self-explanatory; depression associated with epilepsy, however, may merit some
further discussion. Ictal depressions are, in fact, simple partial seizures
whose symp-tomatology is for the most part restricted to affective changes. The
diagnosis of ictal depression is suggested by the paroxysmal onset of
depression (literally over seconds): although such simple partial seizures may
last only minutes, longer durations, up to months, have also been reported.
Interictal depressions, rather than occurring secondary to paroxysmal
electrical activity within the brain, occur as a result of long-lasting changes
in neuronalactivity, perhaps related to “kindling” within the limbic system, in
patients with chronically recurrent seizures, either grand mal or, more
especially, complex partial (Indaco et al.,
1992; Perini et al., 1996). Such
interictal depressions are of gradual onset and are chronic.
Depression occurring
as part of certain neurodegenera-tive or dementing disorders is immediately
suggested by the presence of other
symptoms of these disorders, such as dementia or distinctive physical findings,
for example, parkinsonism.
The miscellaneous
or rare causes represent, for the most part, the “zebras” in the
differential for depression, and should be considered when, despite a thorough
investigation, the diagnosis of a particular case of depression remains
unclear.
Although the foregoing list of possible causes of
depression due to a general medical condition is long, utilizing it in the
clini-cal evaluation of depressed patients need not be burdensome. Evidence for
most of the precipitants, diseases with
distinctive features and neurodegenerative or dementing disorders will be uncovered in the course of a
standard interview and examina-tion and, after using the list a few times, the
physician will imme-diately recognize their diagnostic relevance. The miscellaneous or rare “zebras,” as with zebras in any other branch of medicine, are only considered when one is at the
end of one’s diagnostic rope, a situation often reached when patients fail to
respond to treatment which, if the diagnosis were correct, should have led to
relief, but did not.
Depression is the most common of psychiatric
symptoms and al-though, as noted earlier, the vast majority of cases of
depression occur as part of one of the primary depressive disorders (most
commonly major depressive disorder), depressions due to a gen-eral medical
condition, in certain settings, should nevertheless, by virtue of their
frequency, receive prime diagnostic considera-tion. Examples include treatment
with ACTH or prednisone as in multiple sclerosis or collagen–vascular diseases
and cases of cerebral infarction involving the left frontal area.
Most medication-induced depressions begin to clear
within days of discontinuation of the offending medication; depression as part
of withdrawal from stimulants or anabolic steroids clears within days or weeks,
and from anticholinergics, within days. Post-stroke depression, as noted above,
typically remits within a year. The course of depression secondary to head
trauma or whiplash is generally prolonged, though quite variable. Most of the
other conditions or disorders in the list are chronic, and depression
oc-curring secondary to them likewise tends to be chronic: excep-tions include
depression in multiple sclerosis, which may have a relapsing and remitting
course, corresponding to the appearance and disappearance of appropriately
situated plaques.
Treatment efforts should be directed at relieving, if possible, the underlying cause. When this is not possible, antidepressants should be considered. Controlled studies have demonstrated the effectiveness of both nortriptyline (Robinson et al., 2000) and citalopram (Anderson et al., 1994) for poststroke depression, and nortriptyline for depression seen in Parkinson’s disease (Anderson et al., 1980). For other secondary depressions, citalopram is prob-ably a good choice, given its benign side-effect profile and notable lack of drug–drug interactions; nortriptyline should be used with caution in patients with cardiac conduction defects (as it may pro-long conduction time) and in those at risk for seizures as in head trauma as this agent may also lower the seizure threshold.
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