I believe this game has contributed to the healing process of my depression by assisting in the re-training of my brain's reward cycle system.
For a couple years I stopped doing all my favorite things and only wanted to sleep. I forced myself to do my job, but felt no satisfaction. I forced myself to do my chores but didn't feel good when they were finished. I would sometimes even force myself to play a video game, thinking I could just force normality back into my life.
In one of these "game-forcing" moments I started up Factorio and sarcastically said to myself "yeah, Christopher, the game you've always been too dumb for is going to magically click on your 4th attempt." But, it did!
Sometimes I think games appeal to us because--while offering us an escape from life--they do emulate life in ways our minds find comfortable. We are given "problems" to solve, tools to do it with, and the resources to make it possible.
Factorio has this appeal. It's enjoyable because the challenges are manageable. Problems are fixable. Tools are plentiful. And the resources are in large patches visible clearly on the map. You have "problems" like life, but they are offered in a way that makes them fun to solve, and the rewards come quickly. Futhermore, your "rewards" from solving a problem are often ideas! You'll take these ideas and either use them to cleverly solve problems, or just do fun stuff. Again like life -- there are prescribed challenges, but you can also just goof off a bunch.
After hundreds of hours of dissociating from life and just playing this game (please understand I'd have otherwise just been dissociating anyway) it was bringing life back to parts of my brain. I wanted to come back to the computer and try stuff I'd thought of while I was away. I was actually wanting something again.
The execution of all my little ideas was rewarded quickly and predictably. My failures were often enormously entertaining. I never felt the urge to start my game over because whatever inefficiency I wanted to address within my factory could be resolved with the products that very factory had produced!
I definitely felt the "addiction" that others describe with regard to this game. But ultimately when I pulled myself off the computer and made an attempt to return to real life, I found that my reward cycles seemed to be repaired. I *did* feel good about my work. I *did* feel good after completing chores.
Even if this correlation is not causation, it's been a spectacularly fun game.