For centuries it has been recognized that extremes in mood are inherent in the human condition, but distinguishing mood alterations that are pathologic from those that are not has been an elusive problem until recently. The realization that major mental disorders are psychobiologic phenomena resulting from abnormal brain mechanisms together with the development of a more empirically based diagnostic classification scheme has now made it possible for clinicians to distinguish consistently between abnormal mood states and the normal evanescent changes in feeling tones that are a part of everyday life.
Recent surveys indicate that 5 to 6 percent of the adult population in this country is suffering from clinically significant mood or affective disorders. The major affective disorders are a heterogenous group of mental disorders characterized by extreme exaggerations and disturbances of mood and affect which also affect cognitive and psychomotor functions. There is a marked tendency to periodicity and recurrence throughout the patient’s lifetime, in which diagnosable affective episodes appear and remit and are followed by symptom-free periods (euthymia) lasting weeks, months, or years. The two most prevalent and important diagnostic syndromes among the major affective disorders are major depression and the bipolar disorders.
To reduce diagnostic heterogeneity, the major affective disorders are divided into those depressed patients with a history of manic episodes (bipolar) and those who manifest episodes of depression only (unipolar). The unipolar-bipolar distinction is a useful dichotomization in regard to clinical characteristics, life course, and treatment. Evidence continues to accumulate indicating that unipolar and bipolar depressions are, in all likelihood, psychobiologically different but very closely related disorders. An additional diagnostic dichotomization which has also been helpful in reducing heterogeneity among those disorders is the primary-secondary distinction. The rationale behind this is that affective disorders occurring in a pure form are likely to be more similar than affective disorders which coexist with other psychiatric or medical conditions. A major affective disorder is primary when the affective episode (manic or depressive) is the first-appearing psychiatric illness in a patient’s lifetime and is not associated with other psychiatric or medical illnesses. Conversely, an affective disorder is classified as secondary when it appears in conjunction with other psychiatric or medical conditions. For example, depressive episodes can be observed in conjunction with virtually every mental disorder, for example, schizophrenia, alcoholism, dementia, and personality disorders. Affective disorders can also be associated with medical diseases and occur during treatment with commonly prescribed medications. The diseases associated with depressive disorders include the following: endocrinopathies (Cushing’s disease, hyper- or hypothyroidism), collagen diseases (systemic lupus erythematosus), cardiovascular diseases (congestive heart failure, myocardial infarction), neurologic diseases (multiple sclerosis), infections (hepatitis, influenza), malignancies (pancreatic adenocarcinoma), metabolic disorders (porphyria), and vitamin deficiencies (vitamin B, deficiency, nicotinic acid deficiency). In addition, the chronic administration of the following medications can also precipitate an affective episode: corticosteroids, alpha-methyldopa, propranolol, benzodiazepines, reserpine derivatives, and i.-dopa. It should be noted, however, that even though an affective episode may be classified as being secondary, it can be the most important and compelling aspect of a patient’s clinical picture requiring immediate and specific therapeutic intervention.
The diagnosis of a clinically significant affective episode is based upon the criteria contained in the third edition of the Diagnostic and Statistical Manual (DSM-III). This method of diagnostic classification has been developed and approved by the American Psychiatric Association and is the standard diagnostic system in use in this country today. There are two general types of affective episodes which manifest in patients: major depressive episodes and manic episodes. Most experienced clinicians require that the dysphoric mood or the euphoric, expansive, or irritable mood be persistently present for at least l week before these two diagnoses are considered.