Depression 101

Depression: Definitions and diagnoses


Major depressive disorder, or clinical depression, is a common but serious mood disorder that is much more than unhappiness. People with depression often feel sad, empty or irritable for long periods of time. Depression causes changes to the body (e.g., sleep problems or appetite problems) and the mind (e.g., trouble concentrating), which can affect people’s day-to-day functioning (APA, 2013).

There are several types of depressive disorders (APA, 2013), including:

    major depressive disorder (includes major depressive episode)
    persistent depressive disorder (a persistent low mood)
    substance/medication-induced depressive disorder
    depressive disorder due to another medical condition.

In addition, many people experience seasonal affective disorder (SAD), which is linked to the weather and the time of the year; some women experience premenstrual dysphoric disorder, which includes symptoms of severe depression, irritability and tension before their period; and approximately 10 per cent of women will experience postpartum depression after they give birth (CAMH, 2012).