October 5th is National Depression Screening Day. Like screenings for other illnesses, depression screenings should be a routine part of healthcare. Mood disorders have many symptoms and approaching them clinically involves first constructing a diagnosis from a given patient's symptom profile. An accurate differential diagnosis of depressive illness and other psychiatric comorbidities is needed before the most effective treatment plan can be adopted. The diagnosis of a major depressive episode requires the presence of at least five symptoms, only one of which is depressed mood (Figure 1).

However, mood disorder symptoms occur along a spectrum, with the polar ends consisting of pure mania or hypomania and pure depression. Patients can also experience simultaneous symptoms of both poles. This is referred to as mania/hypomania with mixed features of depression, or depression with mixed features of mania. Patients may experience any combination of these symptoms over the course of the illness. Subsyndromal manic or depressive episodes may also occur, in which case there are not enough symptoms or the symptoms are not severe enough to fit the diagnostic criteria for one of these episodes. The presentation of mood disorders can vary widely, both between individuals and within the individual patient.

While they may have similar symptoms, the long-term outcomes differ between patients with bipolar depression versus unipolar depression, thus treatment approaches are different. The wrong treatment approach could have debilitating effects on the patient's quality of life and missed or delayed diagnosis is common. It is important to make an accurate and early diagnsis.

Reference:
Stahl SM. Stahl’s Illustrated Treatments for Mood Disorders. Cambridge University Press; 2023.