Short term it can. From how I understand it and what I have read, Dark Chocolate and 100% cacao help.
"Dark chocolates can increase the production of endorphins and serotonin in the human brain. As many of us may be aware, serotonin is one of the main neurotransmitters in the brain whose levels affect moods; lack of serotonin can cause depression. Therefore, any boost in the production of serotonin is welcome, especially in people going through depression. In this regard, it is true that dark chocolates reduce depression."
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4696435/
Also antioxidants in the 100% cacao.
Now I am not saying sugar free chocolate is the best thing for that or anything. But I take a lot of preventative measures and do activities that help me stay away from ever being depressed.
i just read all of the answers above and i would try the mix @rawutah uses, my intuition on this is (from his blogs) he is the real deal. not to say many had regiments we should all be doing. the issue is cost and time. many of us work long hours sitting in a dark office, which doesnt help matters. a few people swear by cacao, it has never worked for me personally but thats not to say it will not help others. that happens a lot with me though. also i feel we are talking about someone living with SAD and for many that happens as soon as autumn hits, we all get a bit of this as the human body gets ready to adjust to winter. if you do not have this issue or do not live in seasonal changing environment this may be why? also, so many people i know have to live like the list enjoyinglife put on here, which can be very overwhelming to somone living with depression and/or a mix of that and what others have written. each body is so different and not one thing works.
I would say I don't have seasonal depression, I do live in a place that gets all seasons. There are a lot of different things that work for me that may not work for others. One of the best things that can be done is a cardio workout.
For my own personal self, the self medication that works the best for me is playing extremely competitive video games when I feel anxious or nervous. When playing video games I find myself able to focus and enjoy myself instead of worrying or feeling low.
Some days I need to play for extended periods of time, other days I don't need to play at all. Sleep is another issue for me as my body I think is very nocturnal or whatever that would be called, I naturally LOVE to stay up late!!!