Post-Traumatic Stress Disorder (PTSD) is a mental disorder that may develop after exposure to exceptionally threatening or horrifying events. While many people show remarkable resilience and capacity to recover following exposure to trauma, some may experience (delayed) effects. Symptoms include persistent intrusive recollections, avoidance of stimuli related to the trauma, negative alterations in cognitions and mood, and hyperarousal.
During World War I (1914-1918), some symptoms of present-day PTSD were known as 'shell shock' because they were seen as a reaction to the explosion of artillery shells. Symptoms included panic and sleep problems. Shell shock was first thought to be the result of hidden damage to the brain caused by the continued impact of the explosion of shells near the front. Thinking changed when soldiers, who had not been near explosions, had similar symptoms. If you were lucky, you were diagnosed as having 'war neuroses', if you were not then you might be lacking in 'moral fiber', called a coward or a malingerer.
During World War I, treatment was varied. Soldiers often received only a few days' rest before returning to the front. For those with severe or chronic symptoms, treatments focused on daily activity to increase functioning, in hopes of returning them to productive civilian lives. In European hospitals, hydrotherapy (water) or electrotherapy (shock) were often used along with hypnosis.
A vivid account of the delayed reactions of shell shock can be read in Elaine di Rollo's novel 'Bleaky Hall', which revolves around a group of traumatized World War I veterans in a crumbling, rumbling hydropathic institution.
The diagnosis evolved over time: During World War II, the diagnosis of shell shock was replaced by Combat Stress Reaction (CSR), also known as 'battle fatigue'. In 1952, the American Psychiatric Association (APA) produced its first Diagnostic and Statistical Manual of Mental Disorders (DSM-I), which included the diagnosis 'gross stress reaction'.
Despite growing evidence that exposure to trauma was associated with psychiatric problems, this diagnosis was eliminated in the second edition of DSM (1968). The DSM-II (1968) included 'adjustment reaction to adult life' which was clearly insufficient to capture PTSD-like conditions. In 1980 Post-Traumatic Stress Disorder was added to the DSM-III. DSM-5 (2013) lists the 20 symptoms required for PTSD to be diagnosed, separated into four groups. All symptoms must be associated with the traumatic event.
 Bisson et al: Post-traumatic stress disorder in British Medical Journal – 2015