People with small penis syndrome suffer mentally due to severe anxiety about their length and size when they don't have a small penis. Also known as penile dysmorphic disorder (PDD), it's a type of body dysmorphic disorder that interferes with reality perception. The average penis size is 5.17 in. when erect and 3.61 when flaccid. The primary symptom is a constant comparison of their size and dissatisfaction to the point it affects their daily activities and life. Therapy and understanding of their triggers can help people suffering from this syndrome.