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Chapter: Essentials of Psychiatry: Mental Disorders Due to a General Medical Condition

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.

Mood disorder with Depressive Features

 

Definition

 

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.

 

Etiology and Pathophysiology

 

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.

 

Assessment and Differential Diagnosis

 

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.

 

Epidemiology and Comorbidity

 

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.

 

Course

 

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

 

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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Essentials of Psychiatry: Mental Disorders Due to a General Medical Condition : Mood disorder with Depressive Features |


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