Although depression has been around since perhaps the beginning of human civilization, the disorder has only come into focus in recent decades. Like many other mental disorders—such as Post-Traumatic Stress Disorder (PTSD), which used to be referred to as “shell shock”—depression has long been misunderstood, misdiagnosed, or unrecognized.

The ancient Greeks first recorded depression, or depression-like symptoms, in Western Civilization by calling it “melancholia.” Centuries later, English romantic writers such as Lord Byron and William Wordsworth recognized melancholy as part of one’s creative temperament, though what they were describing was perhaps closer to “manic-depressive” symptoms, where an individual may experience high highs and low lows. By the time Freudian psychoanalysis emerged on the scene in the late nineteenth and early twentieth centuries, much of Freud’s ideas relegated mental illness to repressed sexual feelings.

Freudian psychoanalysis continued to hold sway in the psychology community for decades. But shortly after it emergence, behaviorism—or, the idea that human actions were largely the result of environmental inputs and conditioning—took hold. That said, however, behaviorists didn’t have much to say (or they didn’t have much to offer) with regard to internal mental states such as depressed feelings. B. F. Skinner, who was one of the leading figures of behaviorism, famously called the human mind a “black box.” It wasn’t until the 1950s, when behaviorism was on the decline, when therapists and psychology in general began to look more seriously at defining and treating depression.

This brief history explains, in part, why depression has been so hard to understand. It is also hard to understand because the human mind is perhaps the most complex piece of machinery we have ever encountered.

In the 1950s, a new type of thinking emerged, cognitive behavioral therapy (CBT). According to this branch of psychology, unpleasant thoughts and feeling emerge as the result of “irrational beliefs.” Albert Ellis, who pioneered this school of psychology, argued that patients need to change the way they view events around them and, as a result, their depressed thoughts and moods will eventually change. In conjunction with medications, CBT has proved to be an exceptionally successful approach to treating depression and depression-like symptoms.

Like many areas of psychology, these days psychologists may conduct research on age differences and depression, gender and depression, substance abuse and depression, sleep deprivation and depression and so on. There are many ways to view the problem. Others, such as Michel Foucault, the French postmodern intellectual, outright denied that mental health was even a disorder. According to Foucault and other like-minded “social constructivists,” mental health disorders are only the result of a social misunderstanding, and not—as currently is understood—the result of complex factors such as genetics, family history, and distorted thinking. Although ideas like Foucault’s remain interesting, few professionals today take seriously the idea that depression is primarily a social construct.

Finally, psychology has come a long way since the time of the Greeks or since the time of Keats and Wordsworth, when depression was hardly discussed or understood. These days, a myriad of treatment options such as talk therapy or medications exist to help tackle depression.

In sum, if we were to “cognitively reframe” (a method used in CBT) this brief history tour of depression, perhaps we could say that at least signifiacant headway has been made in defining, identifying, and treating this very real and very crippling disorder.