Night for 6 months...

I think it would influence us both physically and mentally. I've been to Alaska a few times (thankfully always in the summer) and I know it really messed with my sleep cycles. My brother's family lived there for several years and really disliked it, especially in the winter. They said they could get used to the long daylight because they could just put up heavy window covers. Howver, the long nights in the winter made them all quite depresssed. I doubt that I could handle it for very long. It takes a pretty unique person to live there long term.

I definitely think six months of night could have a significant impact on both your mental and physical state. Sunshine and light just make people feel good. When it's dark all the time, people get groggy and tired. You'd have a harder time waking up and going to bed, because there is nothing to differentiate between night and day. People who don't get enough exposure to light also can become depressed.