Abstract: An apparatus, and related method, for determining one or more association variables is described. The apparatus includes at least one processor, at least one memory, and at least one program module stored in the memory configured to be executed by the processor. The program module includes instructions for selecting a subset of temporal onsets in a set of temporal onsets, instructions for determining a statistical relationship between the subset of temporal onsets and a pattern of occurrence of a variable, and instructions for identifying the variable as a migraine variable in accordance with the statistical relationship. The subset of temporal onsets includes one or more onsets corresponding to one or more migraines experienced by at least one individual, and the set of temporal onsets includes the subset of temporal onsets and one or more temporal onsets corresponding to one or more additional headaches experienced by at least the one individual.