The Dane is in the second season of a two-year loan with Gladbach and has denied reports he has agreed to sign permanently.
Christensen told BILD: "I have not yet decided. I'm not going to do so at the moment.
"When it comes to me, I'll decide next summer."
He added: "For me, both things are possible. I want now just to have my mind entirely free. I will not let it distract me, but focus fully on the difficult tasks with Borussia.
"And finally I can also not decide this alone. The question however is also for some clubs."