For me personally, I missed a lot of events and activities, but still was able to maintain a relationship, and while I definitely became less close to some friends who weren't on the same school path as I was, I gained several close friends who were also working in labs. I'm not sure how this school had things set up, but, I had my own lab/office. And in micro there were 3 other spots like mine for students. And then we had a room for disposal, autoclaving, and general "house keeping" and then we had a conference room. Most of us bonded in the last two rooms, and would often help each other out when making plates or cleaning and we would eat together often. I never felt alone, even if it was 2am, there was a chance there would be some other poor student or professor at work.
However, I could see how someone could choose to withdraw from others if they wanted to. To me that would indicate a lack of work. We use to joke that there are two different emotions you feel during lab: elation when something was going right and frustration when you were stuck. Either way, we were always eager to either share good news or vent out our frustrations with each other because really these other students are the only people beside your professors you can relate that stuff to easily.
ETA: I will also add that it was very consuming in the sense that you think about it constantly. Projects like these often mean trekking to the lab at bizarre times to carry out parts of the experiments that are time limited...I.e. Collecting DNA as several stages, where timing is important. So there was very few times where I had a day without thinking about it or tending to my microbes. It's almost like a baby that requires constant care and attention.