A nationwide shortage of popular medications for ADD and ADHD is causing trouble for parents whose children rely on them. In the past two weeks, Ritalin and Adderall, along with their generic versions, have been added to the Food and Drug Administration’s growing list of drug shortages. Some distributors are citing manufacturing delays and increased demand as the reasons. In the United States, 5.4 million children between the ages of 4 to 17 have been diagnosed with ADHD, 66 percent of them take medications to control their symptoms. The drugs are taken daily and when a patient misses even one day, the symptoms can come back very quickly. Last year, sales of ADHD medications totaled more than $1.2 billion.