The invention relates to a trigger mechanism for a drug delivery device comprising at least one energy storing element, an actuation element and a series of cascaded trigger elements. The trigger elements are pre-stressed with increasing pre-stressing and coupled to the at least one energy storing element such that the trigger elements, upon exerting a sufficient actuation force (Fa, U) on the actuation element, cause a cascaded release of increasing portions of energy stored in the at least one energy storing device. At least one of the trigger elements is equipped with a latch element directly coupling at least two trigger elements such that the latch element restrains at least one of these trigger elements to its pre-stressed state before exerting the actuation force (Fa, U).