Should I switch labs, three years in? I'm in a biology PhD program, and I'm three years into the process. However, my mentor is small minded, unsupportive, and borderline emotionally abusive. I found this out almost a year into my project after TAing his class for him, where he treated the other TA with a lot of deference and respect but was really aggressive and unkind towards me. When I spoke with him about realizing that microbiology wasn't my passion, he told me that I should switch labs because this really wasn't the place for me. At the end of that discussion he said I shouldn't hold him to the mean things he'd said (which is exactly the kind of emotional abuse I'm talking about).

For a long time I've considered switching from wet lab benchwork to computational biology, but am worried that the problem lies within me, and not with the work. Now that I've realized that my mentor isn't going to be of any help, I'm turning towards the internet hivemind. In short, my questions are:

A) What criteria have people used to decide to switch the scope and focus of their PhD projects when faced with an emotionally abusive mentor who has led to the emotional breakdown of at least two, if not more, of his students?

B) what is a good way I can assess if computational work is something I would like/be good at?

This also isn't something I can easily go to the department with, because the last time I tried to speak with someone they launched an investigation into the lab and so it ended up making my experience much, much harder.
Almost all grad students feel under-appreciated by their mentors at some point.

Your adviser sounds like a top notch A-hole. Unfortunately, to be a successful researcher in academia, most institutions look at (in order): the quantity of grant money being generated, the quantity/quality of research publications, and how many PhD students you generate. In other words, most research faculty consider the needs of their PhD students last.
Therefore almost all grad students feel under-appreciated by their mentors at some point. What keeps most grad students going through the 'tough times' is they enjoy the subject-matter they decided to go to grad school in. What I recommend is:


Have you began work on a thesis paper? If not, I would consider the door wide open to a change of departments / research groups. Especially if you don't have a passion for your work. Any future career path is going to be influenced heavily by your choice of research; why go down a path you know you don't want to pursue?
Finding a major professor who can simultaneously be your academic mentor and best pal is hard. You are going to need to pick a field of research you have a passion for if you plan on making it to the end. If finding someone you get along with is important to you, the easiest way to tell is to rely heavily on the next bullet:
When looking into another graduate course of study / department / laboratory, ask the current graduate students. This is going to be by far the most useful input: if at all possible, ask them about their relationship with faculty. Ask them about their workload. Ask them if they publish. Ask them if they feel supported. Ask them how long it takes.