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I work in a team of about 10 people, in a large office in a large organisation.
I sometimes get into bad spaces, where I stop exercising, eat badly, sleeping habits get shot etc, it's a self-destructive cycle. These spells are very much a vicious circle (wake up feeling bad, so continue eating unhealthily/don't go for exercise, feel worse, don't want to talk to people... etc) When this happens, the primary effect it has on work is that I lose focus (I work as an IT developer), I get to work late (we have flexible hours, so this isn't a huge problem, but still looks bad).
Now this has been an ongoing thing as part of my life, and the good news is, I appear to be getting better at managing it, in terms of recognising triggers, and turning things around before it gets too bad.
Now one thing is - I'm not sure that you can call this clinical depression. Certainly I haven't been diagnosed as such. I have talked to my GP about it before, and he said that I'd appear to be on the mild end of the spectrum.
Rather, we could possibly think of it in terms of addiction and habits. Think - somebody in the workplace who is a recovering alcoholic, who occasionally falls off the wagon, and who's workplace performance suffers then. The point here is, 'suffering from depressive spells' shouldn't be used as an excuse for bad work performance. It's my responsibility to improve myself, just as it would be my responsibility to upskill and make myself more valuable to an organisation.
My own assessment of my work ability and work ethic, is that I'm pretty good otherwise, in terms of being focused and work, producing high quality work, and contributing to the team. But that said, I pretty sure my colleagues also see me as a bit flakey, after I come in late etc. I think that they can probably see both sides, the guy who does work hard, and produces good work, and the guy who also comes in late and appears to be not focused.
Now, one of the things in terms of managing these spells, is talking about it. The reason for this, is that the thing that makes it worse, is being embarrassed about it, and so withdrawing further and becoming more socially isolated. By talking to others about it ('I had a bad weekend, felt depressed, and ate badly'), you can get some perspective and realise 'This really isn't so bad', and move on from it.
I've been in one of these spells for the last week. I took one sick day, and turned up late on a couple of the days.
I'm considering talking to my colleagues about it. There are two reasons why I might do so.
1) To explain why my work performance is sometimes of kilter.
2) For my own managing of these spells.
I don't mean that I would broadcast 'Oh hey, I have these depressive spells lolz'. But rather, if I'm talking to a colleague who I trust and they ask how my weekend was, perhaps mentioning then that I've been in a bad space for the past week.
There's also whether I mention it to my team leader.
The concern is, that this simply isn't appropriate for a workplace, and that managing my moods is simply my own personal responsibility, not something for my colleagues to have to worry about. I can always talk to other people (ie friends) about it.