Theres two potential questions actually going on here (which are both important for those in a university setting to be aware of):
intellectual burn out, in which case something as simple as reading about some range of topics different from the current research focus or forcing weekends to be about rest and some sort of physically demanding hobby (such as indoor climbing) will do a world of good.
deeper issues than just burnout management, in which case it would be appropriate to at least investigate talking with the on campus mental health staff to figure out how to manage the underlying issues. There are a whole range of mental health issues which only manifest or become obvious in a person's early to mid 20s, and which need professional assistance and/or medication to substantially improve the person's quality of life
