“Depres­sion,” the TED-Ed video above informs us, “is the lead­ing cause of dis­abil­i­ty in the world.” This may be a hard fact to swal­low, the prod­uct, we might think, of phar­ma­ceu­ti­cal adver­tis­ing. We all feel down from time to time, we think. “Then cir­cum­stances change, and those sad feel­ings dis­ap­pear.” Isn’t it like this for every­one? It is not. “Clin­i­cal depres­sion is dif­fer­ent. It’s a med­ical dis­or­der, and it won’t go away just because you want it to.”

Depres­sion can linger for up to two weeks, and become so debil­i­tat­ing that suf­fer­ers can­not work or play. It inter­feres with impor­tant rela­tion­ships and “can have a lot of dif­fer­ent symp­toms: a low mood, loss of inter­est in things you’d nor­mal­ly enjoy, changes in appetite, feel­ing worth­less or exces­sive­ly guilty,” rest­less­ness and insom­nia, or extreme lethar­gy, poor con­cen­tra­tion, and pos­si­ble thoughts of sui­cide. But sure­ly we can hear a paid pro­mo­tion­al voice when the nar­ra­tor states, “If you have at least 5 of those symp­toms, accord­ing to psy­chi­atric guide­lines, you qual­i­fy for a diag­no­sis of depres­sion.”

What we don’t typ­i­cal­ly hear about in phar­ma­ceu­ti­cal ads are the mea­sur­able phys­i­o­log­i­cal changes depres­sion writes in the brain, includ­ing decreased brain mat­ter in the frontal lobe and atro­phy of the hip­pocam­pus. These effects are mea­sur­able in humans and rats, in study after study after study. But while most of us know the names of a neu­ro­trans­mit­ter or two these days, not even neu­ro­sci­en­tists ful­ly under­stand the biol­o­gy of depres­sion. They do know that some com­bi­na­tion of med­ica­tion, ther­a­py, and, in extreme cas­es elec­tro­con­vul­sive treat­ment, can allow peo­ple to more ful­ly expe­ri­ence life.

Peo­ple in treat­ment will still feel “down” on occa­sion, just like every­one does. But depres­sion, the explain­er wants us to under­stand, should nev­er be com­pared to ordi­nary sad­ness. Its effects on behav­ior and brain health are too wide-rang­ing, per­va­sive, per­sis­tent, and detri­men­tal. These effects can be invis­i­ble, which adds to an unfor­tu­nate social stig­ma that dis­suades peo­ple from seek­ing treat­ment. The more we talk about depres­sion open­ly, rather than treat­ing as it as a shame­ful secret, the more like­ly peo­ple at risk will be to seek help.

Just as depres­sion can­not be alle­vi­at­ed by triv­i­al­iz­ing or ignor­ing it, the con­di­tion does not respond to being roman­ti­cized. While, indeed, many a famous painter, poet, actor, etc. has suf­fered from clin­i­cal depression—and made it a part of their art—their exam­ples should not sug­gest to us that artists shouldn’t get treat­ment. Sad­ness is nev­er triv­ial.

Unlike phys­i­cal pain, it is dif­fi­cult, for exam­ple, to pin­point the direct caus­es of sad­ness. As the short video above demon­strates, the assump­tion that sad­ness is caused by exter­nal events arose rel­a­tive­ly recent­ly. The humoral sys­tem of the ancient Greeks treat­ed all sad­ness as a bio­log­i­cal phe­nom­e­non. Greek physi­cians believed it was an expres­sion of black bile, or “melaina kole,” from which we derive the word “melan­choly.” It seems we’ve come full cir­cle, in a way. Ancient humoral the­o­rists rec­om­mend­ed nutri­tion, med­ical treat­ment, and phys­i­cal exer­cise as treat­ments for melan­cho­lia, just as doc­tors do today for depres­sion.

But melan­choly is a much broad­er term, not a sci­en­tif­ic des­ig­na­tion; it is a col­lec­tion of ideas about sad­ness that span thou­sands of years. Near­ly all of those ideas include some sense that sad­ness is an essen­tial expe­ri­ence. “If you’ve nev­er felt melan­choly,” the nar­ra­tor says, “you’ve missed out on part of what it means to be human.” Thinkers have described melan­cho­lia as a pre­cur­sor to, or inevitable result of, acquir­ing wis­dom. One key exam­ple, Robert Burton’s 1621 text The Anato­my of Melan­choly, “the apogee of Renais­sance schol­ar­ship,” set the tone for dis­cus­sions of melan­choly for the next few cen­turies.

The scientific/philosophical/literary text argues, “he that increaseth wis­dom, increaseth sor­row,” a sen­ti­ment the Roman­tic poets turned on its head. Before them came John Mil­ton, whose 1645 poem Il Penseroso address­es melan­choly as “thou God­des, sage and holy… Sober, sted­fast, and demure.” The deity Melan­choly over­sees the con­tem­pla­tive life and reveals essen­tial truths through “Gor­geous Tragedy.”

One of the poem’s lofti­est themes showed the way for­ward for the Roman­tics: “The poet who seeks to attain the high­est lev­el of cre­ative expres­sion must embrace the divine,” write Mil­ton schol­ars Kather­ine Lynch and Thomas H. Lux­on, “which can only be accom­plished by fol­low­ing the path set out in Il Penseroso.” The divine, in this case, takes the form of sad­ness per­son­i­fied. Yet this poem can­not be read in iso­la­tion: its com­pan­ion, L’Allegro, prais­es Mirth, and of sad­ness says, “Hence loathed Melan­choly / Of Cer­berus, and black­est mid­night born, in Sty­gian Cave for­lorn / ‘Mongst hor­rid shapes, and shrieks, and sights unholy.”

Rather than con­tra­dict each oth­er, these two char­ac­ter­i­za­tions speak to the ambiva­lent atti­tudes, and vast­ly dif­fer­ent expe­ri­ences, humans have about sad­ness. Fleet­ing bouts of melan­choly can be sweet, touch­ing, and beau­ti­ful, inspir­ing art, music, and poet­ry. Sad­ness can force us to reck­on with life’s unpleas­ant­ness rather than deny or avoid it. On the oth­er hand, in its most extreme, chron­i­cal­ly intractable forms, such as what we now call clin­i­cal depres­sion, sad­ness can destroy our capac­i­ty to act, to appre­ci­ate beau­ty and learn impor­tant lessons, mark­ing the crit­i­cal dif­fer­ence between a uni­ver­sal exis­ten­tial con­di­tion and a, thank­ful­ly, treat­able phys­i­cal dis­ease.

Relat­ed Con­tent:

Stanford’s Robert Sapol­sky Demys­ti­fies Depres­sion, Which, Like Dia­betes, Is Root­ed in Biol­o­gy

How Bak­ing, Cook­ing & Oth­er Dai­ly Activ­i­ties Help Pro­mote Hap­pi­ness and Alle­vi­ate Depres­sion and Anx­i­ety

A Uni­fied The­o­ry of Men­tal Ill­ness: How Every­thing from Addic­tion to Depres­sion Can Be Explained by the Con­cept of “Cap­ture”

Stephen Fry on Cop­ing with Depres­sion: It’s Rain­ing, But the Sun Will Come Out Again

Josh Jones is a writer and musi­cian based in Durham, NC. Fol­low him at @jdmagness