What do you think of my colleague's attitude?

My first thought was mental illness of some kind. Is he hard to work with at all? Obviously he doesn’t want to share anything.

Is this an on-again/off-again situation… does he switch back and forth between these two behavioral patterns? Or has he always been the happy/jovial guy and now he’s suddenly not? If it’s the former, it’s likely he’s just having the occasional bad day. If it’s extreme, he may be bi-polar. If it’s the latter, I’d be more inclined to think he’s gone through something significant in his life recently and is either grieving or in a depression. In any case, if he is not interested in sharing his private life with you, there’s not much you can do about it but respect his wishes.

I agree completely with @augustlan.
If you think it is something significant in his life that’s causing this behavior, maybe you could try stopping by his office/cubicle/whatevs with a friendly and casual “how ya doing?” Don’t pressure him to talk at all because it really is none of your business, but maybe he’d appreciate someone reaching out just a little.

I think something could have quite possibly happened in his life, and that he’d rather handle it by himself or amongst friends/family than co-workers. I definitely wouldn’t ask him about it or bring it up to management unless it’s getting in the way of his or your work. It sounds personal.

Having a devastating illness in your own life or that of someone close to you, experiencing the death of someone close, and undergoing extreme marital stress (such as having your partner leave you) are some of the things that can produce reactions like this.

A woman in my group was out sick for a while and was uncharacteristically withdrawn when she returned. I sent her an e-mail saying that I had noticed how quiet she’d suddenly become and that I wanted her to know I could listen to anything if she ever needed to talk. She replied that she had been diagnosed with stage 4 cancer, and she thanked me but said she did not want to talk about it or have it generally known. I said nothing more about it to her or anyone else.

I would not have asked her face to face because I respected her privacy. When I myself was in one of those states, a casual “how ya doing?” either would have made me angry because it sounded like idle curiosity about my almost unbearably nontrivial situation or would have caused me to burst into tears. Maintaining composure all day at work was absolutely all I could do, and anything that broke the surface tension would have caused a meltdown. I was grateful that people knew enough to leave me alone.

Just let it be. Enter at your own risk. But I wouldn’t.

Bipolar Disorder. in some people, its like turning a light switch from on to off. experienced this with my granddaughter. psychiatrist finally discovered her problem and put on her on medication. no problems after this as long as she took her meds.

Why not slip this person an unsigned note suggesting there is medication for a bipolar disorder? this may be the key to bring him to stay…......in reality.

A note, maybe. Unsigned, no. Harking back to my own experience, I would not have thanked anyone for implying that I was mentally ill when it was something else altogether. I would have concluded that on top of everything else I was going to have to deal with colleagues who thought I was crazy.

It sounds like he has personal problems that he would like to keep private.

I suspect you’re right. It sounds like he’s got issues / problems at home that he’d rather not become office gossip.

In the U.S. (population about 300 million):

38% divorces per capita per year, which translates to 114 million.

Risk of developing cancer over lifetime (according to the American Cancer Society): men, 50%; women, 33⅓%; that’s 150 million and 100 million, respectively

Cases of bipolar syndrome in the population: about 5 million

All it would take is ONE case of AIDS in one’s immediate life circle, ONE child’s death, ONE overwhelming gambling debt, ONE instance of End Stage Renal Disease, ONE revealed case of incest or extreme abuse, or, for all you know, ONE case of unrequited love to throw someone into a serious funk. Consider how many people have lost their homes and/or are worried about their jobs. Consider how many parents have children who are addicted to drugs. Looking for bipolar disorder as a first explanation when there is a single downturn does not make sense to me.

@Jeruba
Why look for anything? It’s no one’s business. If he comes to anyone with an indication he would like their input they should maybe offer it. Until that time attend to one’s own issues. Most people who want to help are the last people who should and are actually acting from their own dysfunction. Even a psychologist doesn’t offer advice where it’s unsolicited.

@SeventhSense, agreed. All I have really been trying to say is leave him alone. Don’t try to diagnose the poor guy at arm’s length, and don’t butt in on his private misery. Your guesses are probably wrong.

@Jeruba
Yes I see your intent now.

He’s likely got some personal issues and the office is no place to air those