The reverend spoke with Politico Thursday after the Mayo Clinic in Minnesota issued a statement earlier this week stating the Democratic Illinois congressman is receiving treatment there for bipolar II disorder. He has been in treatment there since July 27.
"It's been a challenge," the elder Jackson told Politico. "Jesse has the bipolar thing. It slips up on you. If you bleed, you get a Band-Aid. If you break a leg, you get a splint. This is a combination of forces that we had not seen."
When asked about when his son, who took a medical leave from Congress June 10, would return to work, Jackson said: "The thing about it is, you cannot attach a timetable to it. He has to grapple with, all of us in some sense have to grapple with, the challenges of bipolar and depression and the time we're working through. He's getting good treatment but you cannot ... put a timetable. When will he be back? Well, we don't know. We wish he never would have gone."
Meanwhile, former Rep. Patrick Kennedy, D-R.I., said he traveled to Minnesota to visit the younger Jackson, a longtime friend.
Kennedy said the meeting Thursday made it clear to him the congressman had been "dealing with a deep depression," which has affected him physically.
Kennedy -- who once received treatment for depression and addiction at the same facility -- told NBC News he tried to reassure Jackson about his political future.
"I tried to emphasize there is a future," Kennedy said, pointing out Jackson can serve as an "inspiration" for "showing people this is a serious issue that should be dealt with like any other medical condition."
Kennedy said Jackson deserves credit for making progress and encouraged him to stick with the treatment even when he feels pressure "to get out" and get back to work.