It can be cured without drugs. But it takes will and choice and some key knowledge of the unconscious mind. What often works is a change of environment. When you are depressed, your world increasely becomes depressing. But if you change that world, you will get fresh positive triggers, to distract from the cave of depression. This has to do with how the brain works.
When the brain writes to memory, emotional tags are added to the sensory content. This is useful for many reasons. For one, it allow you to use both sides of the brain when assessing your memory. The left brain is more for the sensory content details, while the feelings tag is more right brain. Depression keeps you in a linear feeling of depression, therefore you; ego, become more right brain and less able to reason from the left brain. You become more emotional all the time, but in a linear way. At the same time, since depression is a type of feeling tag, you unknowingly, reinforce your new memory writing; your world, with the depressed feeling tags. The real time memory is being rewritten in a self fulfilling way by the depression feeling tone and writing process.
The goal is to get yourself more into the left brain, to shift the feeling tone away from the just the linear depression feelings. A new place requires new adaptations, which keep you busy in your left brain; thinking, reasoning, exploring, sensory, etc.
I was chronically depressed when I was young, starting about age 10 to about 25, when I started to explore the unconscious mind and the collective unconscious. This was before the modern self help and drugs we have today. I cured myself with neither. I remember my depression was more seasonal. During the summer, I rarely felt depressed, due to the free time, outdoor activities with friends and family, cookouts, parties, the higher sensory load; bright sunlight, the smells of summer flowers, sounds of bird, sun on my tanned back, summer breeze on my skin, being in and under the water swimming, the bikinis, etc. It shifted my mind in a sensory way and that shifted my feelings. Come the fall and school, I would get bored, and would get depressed. Also I got more shut inside, due to the cold, with more clothes; no sun and breeze on my skin, less lighting, no more swimming, etc. The cave comes back and the depression; stuck in my head.
What may be compounding depression, in many people today, is the internet. The internet can locks you away; desensitized even in summer. It was when I started to explore my own brain, about age 25, that my depression became controllable, year round. This effort took away my depression because even depression was an interesting place to explore, when it comes to the brain and consciousness. I could be depressed and observe. That is the key skill; split your between both sides of the brain. The unconscious would use one side of the brain and me; ego, the other. I was half depressed and half amused and amazed. In the end, that in my head feeling, caused by depression, had trained me to work comfortably, exploring the unconscious mind, like I had been built for that pioneering work.