Depression is one of the oldest recognized mental health conditions in human history, with descriptions dating back more than 2,000 years. What has changed dramatically over the centuries is how people explained it: as a bodily fluid imbalance, a spiritual failing, a chemical deficit in the brain, or a pattern of distorted thinking. Each era’s understanding shaped how sufferers were treated, sometimes with compassion and sometimes with cruelty.
Ancient Greece and the Theory of Black Bile
The earliest systematic attempt to explain depression came from ancient Greek physicians and philosophers, who called it “melancholia,” literally meaning “black bile.” Under the four humors model, health depended on a balance of blood, phlegm, yellow bile, and black bile. An excess of black bile was thought to produce the sadness, lethargy, and hopelessness we now associate with depression.
What made this framework remarkable for its time was that it treated melancholia as a physical illness rather than a punishment from the gods. The Aristotelian text known as Problem XXX.1 explored the idea that black bile could shift between cold and hot states, producing different symptoms. When the bile ran cold, a person would fall into “stupor or irrational despondency or deep depression.” When it overheated, the result was mania, heightened desire, and erratic behavior. This ancient observation that depression and mania could cycle within the same person anticipated, by more than two millennia, the modern concept of bipolar disorder.
Aristotle’s text also raised a striking question: why did so many people who excelled in philosophy, politics, poetry, and the arts appear to be melancholic? The link between creative genius and depression was already a topic of debate in the fourth century BCE.
The Medieval Period: Depression as Sin
As Christianity became the dominant intellectual framework in Europe, the understanding of depression shifted from the body to the soul. The condition most closely resembling depression was called “acedia,” a term used by monks and theologians to describe a state of inner emptiness, inability to pray or perform spiritual activities, and persistent anxiety and irritability. Unlike melancholia, acedia was considered a vice, something the sufferer had developed through their own moral weakness and was responsible for overcoming.
The monk Evagrius of Pontus, writing in the late fourth century, described acedia as “the most troublesome of all” demonic thoughts and called it the commander of the demonic forces arrayed against monks. He linked it to the “noonday demon” referenced in Psalm 90, a force that struck in the middle of the day and drained all motivation. Centuries later, Thomas Aquinas argued that acedia resulted from wavering faith, creating a vicious circle of passivity and negative feelings toward God. The practical consequence of this framing was that people experiencing what we would now call depression were often told they needed more prayer, more discipline, or more faith, not medical care.
Robert Burton and the 1621 Turning Point
The publication of Robert Burton’s “The Anatomy of Melancholy” in 1621 marked a shift back toward treating depression as a condition of the body and mind rather than a spiritual deficiency. Burton’s massive text catalogued different types of melancholy, including what he called head melancholy (of the brain), bodily melancholy (a melancholic temperament), and “windy melancholy” (hypochondria, centered in the liver and spleen). He also identified love, excessive study, and divine causes as triggers.
Burton’s most important insight was that anyone could become melancholic. Your temperament and environment made you more or less vulnerable, but even outgoing, genial people could be stricken. He also noted that these categories rarely appeared in isolation; most people experienced a mixture. This was a sophisticated observation for the era, and the book remained influential for centuries.
Kraepelin and the Birth of Psychiatric Diagnosis
The late 1800s brought the first attempt to classify depression using the methods of modern medicine. German psychiatrist Emil Kraepelin, working from extensive clinical observation, proposed dividing major mental illnesses into two categories: dementia praecox (roughly what we now call schizophrenia) and manic-depressive insanity. Kraepelin based this distinction not on symptoms at any single moment but on the natural history of the illness. He noticed that individual patients frequently transitioned between mania, depression, and mixed episodes over the course of their lives, and that these patterns ran in families. He also observed that people with certain baseline temperaments were more likely to develop acute mood episodes of the opposite polarity, a cheerful person tipping into deep depression, for instance.
This was a foundational moment. For the first time, depression was being studied as a diagnosable medical condition with identifiable patterns, hereditary features, and a predictable course.
Electroconvulsive Therapy and Early Physical Treatments
Before medications existed for depression, clinicians experimented with physical interventions. In August 1939, Italian professor Lucio Bini reported on the first use of electricity to induce a seizure for therapeutic purposes in psychotic patients. The rationale came from an observation that seizure disorders and psychosis seemed to be antagonistic: few people with epilepsy developed schizophrenia, and few people with schizophrenia developed seizures. Spontaneous seizures had occasionally been reported to produce partial or complete remission of psychiatric symptoms.
Electroconvulsive therapy (ECT) became widely used for severe depression throughout the mid-twentieth century. It remains in use today for treatment-resistant cases, though the procedure has been significantly refined from its early form.
The Accidental Discovery of Antidepressants
The first antidepressant medications were discovered entirely by accident in the 1950s, and both stories follow a similar pattern: drugs developed for other conditions turned out to lift mood.
In 1952, researchers Irving Selikoff and Edward Robitzek were studying iproniazid as a treatment for tuberculosis. They noticed the drug “greatly stimulated” the central nervous system, which was initially dismissed as a side effect. By 1957, psychiatrists at Rockland State Hospital in New York had tested iproniazid in depressed patients who did not have tuberculosis and found it effective. It became the first monoamine oxidase inhibitor, or MAOI.
The story of imipramine, the first tricyclic antidepressant, was equally serendipitous. Chemists had synthesized the compound in 1945 by modifying the structure of an antihistamine. Because it looked chemically similar to chlorpromazine, an antipsychotic, it was given to German psychiatrist Roland Kuhn to test in schizophrenia patients. It failed as an antipsychotic, but Kuhn noticed it improved mood. In 1957, at the World Psychiatric Association Meeting in Zurich, he presented the first public report on imipramine’s antidepressant effects.
These two accidental discoveries launched the era of pharmacological treatment for depression and also raised a deeper question: if drugs that altered brain chemistry could relieve depression, what did that say about the underlying biology?
The Monoamine Hypothesis
The success of early antidepressants led directly to the most influential biological theory of depression in the twentieth century. In 1965, American psychiatrist Joseph Schildkraut published a landmark review in The American Journal of Psychiatry proposing that depression might be caused by altered levels of certain chemical messengers in the brain, particularly norepinephrine. That same year, Bunney and Davis published a paper making a similar argument. Two years later, British psychiatrist Alec Coppen proposed that serotonin played a central role.
Because norepinephrine and serotonin both belong to a class of brain chemicals called monoamines, these ideas became collectively known as the monoamine hypothesis of depression. This theory shaped drug development for decades and led to the creation of SSRIs (selective serotonin reuptake inhibitors) in the 1980s and 1990s. While the monoamine hypothesis provided a useful framework, it has since been recognized as an oversimplification. Many patients don’t respond to drugs that target serotonin or norepinephrine alone, and the biology of depression involves inflammation, stress hormones, neural connectivity, and genetics in ways that the original theory did not account for.
Cognitive Therapy and the Psychological Turn
While pharmacology was reshaping treatment, a parallel revolution was happening in psychotherapy. In the 1960s and 1970s, American psychiatrist Aaron T. Beck, originally trained in psychoanalysis, noticed something consistent in his depressed patients: they experienced persistent negative thoughts about themselves, the world, and the future. Rather than focusing on unconscious childhood conflicts, as psychoanalysis did, Beck developed a structured approach that helped patients identify and change these distorted thinking patterns.
He called it cognitive therapy, later known as cognitive behavioral therapy (CBT). It became one of the most studied and widely used treatments for depression, and clinical trials consistently showed it was as effective as medication for mild to moderate cases. CBT also expanded well beyond depression into treatments for anxiety, PTSD, substance use, and other conditions.
Diagnostic Categories and the DSM
The way depression is officially defined has continued to evolve. The Diagnostic and Statistical Manual of Mental Disorders (DSM), published by the American Psychiatric Association, has gone through multiple editions, each refining the criteria. A significant change came in 2013 with the publication of DSM-5, which removed the “bereavement exclusion.” Previous editions had instructed clinicians not to diagnose major depression if the patient’s symptoms could be explained by recent grief. The DSM-5 eliminated that exception, reflecting the view that depression triggered by bereavement is still depression and can still benefit from treatment. The same edition added a specifier for “anxious distress,” formally recognizing the heavy overlap between depression and anxiety.
Culture Shapes What Depression Looks Like
The history of depression is not just a Western story. In China and several other East Asian countries, the diagnosis of “neurasthenia,” a term emphasizing physical exhaustion and bodily symptoms, served for much of the twentieth century as the primary way people described what Western clinicians would call depression. A cross-cultural review found that neurasthenia in China functioned almost as a culture-bound syndrome, overlapping with depression but carrying different social meaning. In cultures where mental illness is heavily stigmatized, framing suffering in terms of physical fatigue and nerve weakness made it more acceptable to seek help.
This distinction matters because it reveals that depression is not simply a biological fact waiting to be discovered. How a society names, explains, and responds to persistent sadness shapes the experience of the people living through it. The physical symptoms, the emotional language, even whether someone seeks treatment at all depend in part on what their culture tells them depression is.