Can jet lag cause a anxiety relapse, how long would it take for anxiety to dissipate after crossing 8 time zones?

Yes, it can: Jet leg can definitely cause a flareup of anxiety disorder. Chances are it will last longer if you traveled west than if you traveled east. People traveling that distance west typically report the flareup lasting 3 to 4 weeks whereas those people traveling east typically report flareup lasting only about a week. Best wishes.

Potentially: Anxiety, irritability, confusion and moodiness have been reported with Jet lag. It usually takes about a day to recover for each time zone crossed.