I find TED about as interesting as a wet napkin. It's where shills, sellouts, and nobody of noteworthy distinguishment talk about nothing with bits of "facts" everyone already heard about from a shitty huffpo article or something, which more likely than not is either outright wrong or oversimplified.
What we call depression (and most so-called mental illness, violence, and addictive behavior) I think is a measurement of society's failure to tend to the needs of its people, with suicide being a big 0 in red marker. Psychology/Psychiatry is a tool for the establishment, its primary development and current use is propaganda, hence the term "mentally ill". It's your fault you're miserable, just like it's your fault you're poor. Don't change the system, change yourself, if you take these pills, have happy thoughts, conform to our standards, and do enough yoga then you might "make it". Sure there's all these things we know influence or determine behavior, but in the end it's your choice, despite evidence in practically every field suggesting otherwise. -That's psychiatry, its function is to deflect attention from the status quo, and propagate hyper-individualism to isolate us from our communities.
Psychology is slightly more rooted in some sense of science, but it's more or less a trade in some ways than a profession. Psychology is the art of modern propaganda developed by the US in the early 20th century via the rise of the PR industry. Propaganda aims to control public thought, which is why psychologist are heavily reliant on polls and surveys which are used to read the public thought. When a company or political figure starts a PR campaign they search for a core group of people to target, through mass surveilance and data mining they learn this demographic's likes, dislikes, and can even predict with reasonable accuracy how this group will react to new information before airing.
There are many examples of this throughout the political and "entertainment" industry which are the two most reliant on PR because they're inherently worthless and/or detrimental to society. That's scratching the surface of how US propaganda works, but sums up the purpose of psychology.
"It is known that [Joseph] Goebbels studied the way advertising companies worked in America."
"Propaganda works best when those who are being manipulated are confident they are acting on their own free will."
"You have nothing to fear, if you have nothing to hide" -Joseph Goebels
(Chomsky is a 90-something year old jew btw, he remembers WWII)