Is it possible for two depressed people to "feed off" of one another's depression?

Yes it is possible - probable, actually!

On the surface it can feel like a sort of 'bonding' but given the opportunity to feel better (maybe from a new positive influence), one person is likely to start making excuses to avoid the other. This is because despite the familiarity, a person's unconscious mind is looking for solutions, not reminders of existing troubles.

So the relationship between two depressed people has a limited lifespan - unless hope enters the equation. As soon as one person starts to take an ACTIVE interest in dealing with their problems and sharing their discoveries, the other person's unconscious mind will latch onto the possibility of a solution. They can then spur each-other on to feeling increasingly better with shared insights, discoveries and forward momentum.

Yes it is possible and very dangerous to some degree if you allow too much to happen. You might end up making one another become even more depressed and get lower then normal. Talking to someone else that is depressed is one thing but spending every day with each other and not having positive contacts may be bad for you. Be careful while around someone else that is depressed if you yourself are. Also, be extra careful if you are in a very low mood, because if you are already down very much you may make it even worse for you to the point of suicide.

If a person is suffering from depression then being in intimate contact with another person who also has depression can fuel their problems, yes.

I really think it depends on the individuals involved though and the situation. If both people are committed to overcoming their depression and have a positive approach to it then being around someone else who knows what your going through can be a great support. They can share tips etc.

If a person's depression isn't under control then its unlikely they will have the strength to be able to handle having a relationship with someone in a similar situation to them. If you are too ill to manage your own problems, you're not going to be able to cope with being exposed to someone else's. It will only bring the person/people furthur down, and trying to support the other person will be very draining when you don't have a lot of emotional energy to begin with. It can be a really unhealthy situation.

I've come accross people who seem to want to hold on to their depression so they still have something that connects them to the person or people they mix with who also have depression/mental illness. Its silly but some people with depression can be competative and have a "my problems are worse than yours" attitude. Recovery can be hindered because people can be scared that if they're a bit better, then they are know longer genuinley ill and deserving of support of understanding and help which is of course nonsense.

I think you already know the answer to this question.

Synchronous feelings tend to bring people together. Depression is unique, though, in that it can bring people together who are of similar emotion, but once one party starts to cheer up they leave the second individual. Depression drives happy people away.

When I've been depressed, I've often felt that someone else being depressed too was a relief. I love being able to relate to someone, whereas I just get jealous or angry or upset at happy people.

Generally, it's not the best idea to put two depressed people together. Put them with happy and healthy people instead :D

oh yes just in the same way a depressed soul seeks out all the sad music they can find,sometimes when we are sad even though we don't like it we seem to seek out things to keep us sad upbeat songs and upbeat people would be a better aid to recovery.

Yes.

They reinforce each others depression.