To a degree, no. Both happiness and depression come from chemical compounds in the brain. On the other hand there are definitely ways to keep yourself in a happier and more positive state of mind.
For just this reason it can seem like the best option to just not care, not to involve yourself in other people’s lives at all. Personally I am the other extreme, I often take control of things and try my best to accommodate everyone. This can easily come back to bite you in the ass though, it’s hard to please everyone. A recent lesson I’m learning is that the harder you try the more people resent you. I haven’t figured out yet if it’s caused by jealousy or guilt or something else entirely.
This does definitely play a large part in anxiety disorders though. It’s hard to feel good about making a choice that doesn’t please everyone to some extent. No one wants to be the reason others are unhappy but the truth is that it is the worst to be responsible for your own unhappiness. Staying in a happy state of mind is a bigger challenge to some than others, it can be a lot of work. Again personally, this is the greatest difficulty for me. I have a great deal of fatigue rooted in my chronic pain. Able-bodied people often shrug it off but it takes a lot of energy to be in pain all the time. It takes a lot of strength to carry on with daily chores when you’re in pain, and it even takes a great deal of concentration to think of anything outside of your pain.
This is where addiction comes into play. I believe that even more so than chemical dependency, people become dependent on the lack of pain that comes from drugs and alcohol.
To a degree depression, like many other mentalitys, is out of an individuals control. I do believe though that as an individual people can increase their own happiness with positive thinking and relaxing activity, and even personal health/fitness. When we as a people work towards living a life that produces the greatest amount of natural happiness we as a people can conquer depression. That is our choice.