A common but serious medical illness or mood disorder with symptoms that negatively affect how an individual feels, thinks, acts, or handles daily activities  – depression as defined by scientific experts such as psychiatric/psychological associations, Government-sponsored mental health agencies, research non-profits, and the like. Along with these definitions, PAD also believes that depression is a brain disease, unique to each individual, as with any biological or biochemical disorder. If not treated early, it may hamper adolescent brain development.