If you have read the Harry Potter books or seen the movies the you are acquainted with the dementors, wraith like creatures who control people by sucking every bit of joy out of their souls and leaving despair in their wake. Ms. Rowling is said to have based these characters upon her personal experience of clinical depression, which I can believe because her description of their effect does indeed sound just like a depressive episode.
I have come the conclusion that dementors can take human form as well. When they are in our private lives we can usually control how much and under what circumstances we deal with them. It's more difficult when we confront dementors in the workplace.
The issue is not their depression, if that is in fact their problem, it is their insistence upon inflicting their negativity upon everyone around them. These people do not see the glass as half empty, but as broken beyond repair. And they like it that way. They want everyone else to be just as miserable. Whereas most persons I have known with depression want to be well and happy and wish everyone else to be as well.
I work with a dementor. No matter how good one's mood is upon arrival to work, he will respond with a well rehearsed rant that will send one searching for the Prozac.
Nothing ever pleases him. If management does something nice for employees it is just to make up for some awful thing they have done in the past. He then proceeds to recount in excruciating detail, the previous infraction. If its a bad day he will say "This is just like the time management did..." and then again rant about past injustices. Moreover they have the memory of elephants, so that current management is blamed for the faults of those who have retired long ago, and coworkers are still being tagged with 10 year old mistakes.
This is bad enough when you only have to hear about workplace issues, but the dementor doesn't stop there. For example this person hates sports. Now there's nothing wrong with that, I married a man whose sole interest in things athletic is his son's batting average. But when coworkers cannot have a a casual conversation about last night's score without inciting a lengthy tirade about overpaid athletes and wasted tax dollars, it is all too much.
Slowly the black cloud that surrounds this person creeps across the room until everyone else in the place in drinking the negativity Kool-aid right along with the dementor. A happy job place becomes a drag. An already troubled job place becomes a nightmare.
So what can do about these toxic wonders? The first step is simply realizing what sort of co-worker you are dealing with. Recognize that the bilge they spew is only their reality, its not yours. Remember that every job has its ups and downs. In the Harry Potter books, the Dementors are banished by a spell that requires the recalling of happy memories. And actually the best cure for dementors in the workplace is similar. Find something positive about your job and hold onto it through your toxic coworkers rant. Remind yourself why it is you do this work. You may not be able to banish this workplace scourge, but you can shield yourself from the gloom.
And if all else fails, think happy thoughts of retirement. Yours or theirs.