Psionics are super-powers that come from the brain. It could work off of Willpower, or perhaps a Unusual stat of Psionics.
It is also possible to have a Talent or Focus related to Psionics.
Most common Psionic disciplines then work like SFX.
Psionic is a status unto itself: there are forces that only affect psionics, and there are things that are immune to psionics
Use of Psionics causes Mental exhaustion, and misuse of psionics in many cases causes mental damage.