alarmist

One who causes others to become alarmed without cause.

I don't mean to be an alarmist, but I do think you should prepare yourself for the worst.

No German troops were mobilized along Canada's border last week, no Canadian cities had been bombed, and only by the remotest flight of fancy could alarmists see the Dominion as a battleground.

Of or relating to causing others to become alarmed without cause.

This deliberately alarmist scaremongery has since been repeated on various occasions, notably in Brazil before 1964 and in Chile under Allende.