Post-traumatic stress disorder (PTSD) and acute stress disorder (ASD) are similar mental health conditions. Individuals with PTSD have experienced a traumatic event and later experience uncontrollable thoughts of the episode along with flashbacks, nightmares and severe anxiety lasting for months or years and interfering with normal functioning. Individuals suffering from ASD experience severe stress symptoms in the weeks and months after a traumatic event. If ASD symptoms last longer than a month, an individual might develop PTSD.