(I am not a doctor, this is not medical advice.)
Depression is not one illness with one cause and one method of treatment.
Our knowledge of mental illness is pretty poor.
Since depression can be a fatal illness (and even when not fatal it can be debilitating and lead to awful life outcomes) we need to be careful when offering advice.
> The best medicine for depression is to imagine you were not depressed, think of what you would do, then do it. Even if it doesn't feel quite right, keep moving.
I say this as politely and gently as I can: this is terrible advice for many people. I'm not suggesting that people with depression should be cocooned and protected from everything; that's often harmful. But we need to remember that many people with depression have distorted thinking, and thus asking them to focus on what they would be like if they didn't have depression could cause them very great harm.
> Therapy can be helpful, but it can also be debilitating by causing you to identify with your depression.
I agree that some therapies are terrible. Non-specific counselling is usually awful and does nothing to help, and can make things worse. But some therapy really does work for some people, effectively curing them or giving them techniques to deal with the illness when it strikes.
Notably, Cognitive Behaviour Therapy has good evidence for its effectiveness.
We're still muddling along with pharmacology - there are a raft of different SSRIs / SNRIs / NASAs / etc, and then tricyclics, and then MAOIs. There's some evidence of effectiveness, many people report remarkable changes. But still, we don't know how these meds work, and we don't know how to find better meds.
And some people will not find relief even with good therapy provided by skilled therapists, or with medication, and so they might try one of the more extreme treatments. ECT is still used. It's very different now from the portrayals in popular media (One Flew Over The Cuckoo's Nest is set in 1963) - people are sedated and it's used much less often. I've met a few people who've had it. Some of them loved it and welcomed it, and were keen for the treatment to continue. Others didn't like it, and opted out of further treatments.
If you have depression, and you find something that works for you, that's great. And it's great that you share that information with other people. But please put disclaimers on it. "This is something I tried. I think it worked for me." And please don't make declarations of efficacy unless you have decent research to back it up.