While it may take weeks to manifest and months before it seriously reduces one's capabilities, there's a noticeable transition for me about 5-7 days after I arrive at a polar environment, and another transition after I return to someplace warmer with day-night cycles. I call it, unoriginally, "the wall." Arriving in the field, I spend my first few days frequently shivering, cramming carbs to try to stay warm, and prone to frequent headaches (not due to dehydration, as forcing fluids doesn't help). Then around Day 5 to Day 6, the headaches stop, I'm comfortably warm in my parka and don't need the carbs anymore, I'm generating more body heat. And… my emotions crash, I often feel cranky or despondent. In a day or two my mood lifts, and then I'm fine physically and emotionally for the rest of the field season. Other than finding it a bit harder to concentrate and focus on any one thing.
Coming home, the return to crowds and civilization after living in a desolate wilderness is disorienting, and it is hard to follow all of the threads and figure out what should be done next. And I'm sweating even more than usual (and still burning 3500 kcal/day without gaining weight). After 5-7 days, again, a reverse Wall effect: my appetite plummets, I'm not as warm, I can think in longer bursts… but again my mood crashes, I feel despondent or cranky. Or like I need to push back on *something* just to prove I still exist. And I've typically just gone from action-filled long 18-hour days with strenuous physical activity, to long periods without much to do except catch up on reading. So… I often feel useless post-field, and if I haven't set up lots of return-home socialness, feel alone and aimlessly unwanted. Again, in a couple of days my mood improves and then I'm in a new equilibrium. As a male, I'm unaccustomed to my emotions being tweaked noticeably by my endocrine system (wry grin).
This past Arctic season, I hit the first Wall around Thursday the 15th at Haughton Crater. Just in time for news of a couple of disquieting bombshells from home, which I didn't handle well. It didn't help either that the weather was worsening and we'd just left a broken drill string stuck. (Kudos to tenacious_snail for emotional support online, and dangerpudding for putting up with me in person then.)
On Friday the 23rd, I left the Arctic and headed for Yellowknife and Edmonton and home. The return-Wall hit me around Wednesday-Thursday of last week, leaving me feeling useless and depressed and wary. I was not an easy person to be around, and a crashy venting on FB Friday night led to 30 comments (now made private). This has coincided with a local event that adds stress in one of my relationships, plus another sweetie with a sudden influx of new dating relationships in the past 2 weeks. One of whom stayed over in my house last Friday, so I needed to play friendly-host when I really just wanted to flee.
It hasn't been an easy Wall-transition… usually bumpy, hopefully now things will re-ground and find their new equilibrium.