A nationwide shortage of the medicines used to treat attention deficit hyperactivity disorder is causing those diagnosed with the ailment - or, more often, their worried parents - undue stress. Individuals looking to refill prescriptions are being forced to drive from pharmacy to pharmacy in search of hidden stockpiles of medicines like Ritalin, Adderall, and their generic counterparts. In some cases, calling ahead doesn’t even help, since the medicines are likely to be doled out in the time it takes to get there.