How much stress can cause a late period?

Dr Sarah Jarvis MBE

Stress affects the chemical messengers called hormones which are released from your brain. These hormones then go on to affect other hormones released from your ovaries which normally trigger your periods. Stress or a sudden shock can stop your periods in this way. Usually if this is the case, they resume naturally over some time.

https://patient.info/health/periods-and-period-problems/missed-periods