Depression Quest is imo not a game by definition, but it's an interactive short story about the struggles of daily life from the perspective of a depressed person with motivation, energy, and sleep issues. At the end of each segment you get multiple choices for how to react and proceed.
The most interesting thing is that if you lean too much into your depression and always take the easy route, some of those options are crossed out, so you can't choose them even although you know they would be good options. You still see them and know they're there, but you can't choose them. Instead you're forced to choose an option that you know is bad for you and your health, but you can't help it or do anything against it - just like with a real depression.

As a person who struggled with severe depression since childhood, still suffers regularly, and later with suicidal tendencies as well I can say that this representation of how life feels for a deeply depressed person is the most accurate and most relatable depiction I've ever seen.
100% of what the protagonist feels and describes could've been copied from my diary and dozens of times I felt as if the game had quoted me, like literally word by word, the withdrawn and auto-destructive stuff as well as the hopeful trying-to-survive stuff.

Retarded statements like "pull yourself together", "think positive", or "Why are you depressed? Life is so beautiful" do not work against real depressions and by saying something as ignorant and inconsiderate as this you only make it worse for the depressed person. Depressed people need security instead of guilt trips and assurance instead of being called abnormal.

I also recommend this game for people who already suffer from depression which may sound counter-intuitive and discouraging, but I promise you it's not. Depressed people should try this at least once not because they need to be taught something (although the game does a quite good job with that) or because they need to see how much worse it can get... but to learn one simple but very important thing:
There are people out there who understand what you're going through, even if it seems that no one does. And I'm not talking about therapists only. You are not alone.

There are more important things to learn from this game:

• A strong social support network is essential for coping with depression.
  
• It's important to be able to tell from case to case whether socializing could help you no matter how difficult it feels to agree to it, or if it's too much right now and you need rest.
  
• Don't be afraid to admit that you have problems. Accepting them is the first, HUGE, and very hard step on the road to recovery. Everything after that usually becomes easier.
  
• Taking medication does not brand you a lunatic or make you sick, quite contrary: Medication can really help with depression. The game uses bronchitis as an example, I always use diabetes: Just because the dysfunctional part of your body is [not the lung, but] a gland or a part of the brain, you're not alien or abnormal. You wouldn't be ashamed to replenish your insulin household, then why should serotonin (or anything similar) be a problem? Depression is an illness like any other and there are ways to treat them.
  
• A person that doesn't understand what you're going through has no grounds to judge in any way and shouldn't be taken seriously at all. There's no shame in seeking help from those who do understand you.
  
• And last but not least: Seriously consider getting a pet (or two or a dozen), if you don't already have one. Animals, unlike certain humans, accept you the way you are. If they start to love you, they do it unconditionally. They don't shame you for a lack of energy, instead they're there for you and interacting with them can be extremely soothing. If you feel lonely, but also think that you're unable to spend time with people, a pet is a surefire way to combat loneliness.
  I have 7 cats (and wish for dogs and donkeys, if I could just afford them...), so you can believe me. Anywhere they are is the safest place on Earth for me and I have no idea whether I love them more than they love me or the other way around. They're the second-most enriching part of my crappy life... the best part is my wonderful wife.

Yes, I have a wonderful and understanding wife that I would die for to protect her and that I would do anything for to make her happy... because she's willing to do the exact same thing for me. She's my personal guardian angel and thanks to her and our pets I can finally somewhat enjoy life.
I didn't know that that was even possible, but after playing this game I appreciate her and everything she does for me even more.

And I recommend Depression Quest from the bottom of my heart. The amazing people behind this are geniuses that managed to tackle a very serious and difficult topic in a truly helpful way with something as simple as a semi-interactive short story.
If I was wearing a hat, I would not only take it off for them, but also never put it on again.