Could anything cause an early period?

Stress: Emotional and / or physical stress can osscasionally cause temporary changes in the cycles. Normal variation in cycle length can also make it seem that the period is early, but still be well within the normal range. Cycle lengths vary from as short as 21 days from start of one period to the start of the next - to as long as 36 days between cycles.

Several things: There are a number of factors that regulate cycle length. Everything from stress to other medications to new medical problems can alter cycles. The most important factor is whether the change persists. It is very common for a woman to have 1 or 2 irregular cycles a year and only if this becomes a pattern is there a likelihood of an underlying issue.