Efavirenz is known to cause CNS effects. Symptoms resolve within 3 to 6 months but in some patients may persist until efavirenz is substituted for nevirapine.
Interesting question. It goes hand in hand with the fact that Interferon alpha given treat people with hepatitis C makes around 40% of them develop a full blown major depressive episode. These are people who never had psychiatric problems in their lives. We believe it is a clinical model for inflammation-induced depressive symptoms a theory we work a lot in my lab.