PTSD

PTSD (or Post Traumatic Stress Disorder) is a mental health issue that affects people who have suffered severe traumatic events in the past. It is not well known in the 9th Century, and sadly passed off as the victim having some type of other mental health problem. Unsurprisingly, it could be common during this period. Warfare, improper medical attention, and accidents can be just a small portion of the traumas that many suffer. If left unattended then the trauma can come back at a later date and affect the victim.
Those who have been subjected to violence is a common type of PTSD sufferer. Military veterans and levied troops run a risk of this due to the effects of warfare. Seeing friends and family being killed in gruesome ways can affect the individual, and even seeing the effects of bodily injury on opponents can cause serious & repeatable trauma to an individual. Sometimes, dealing with the effects of raids can cause this, whether through violence to non-combatants  or combatants. Both would be affected. Sometimes innocents are caught in the cross-fire, such as children who end up suffering when their caregivers are violated or killed, or in cases of rape and sexual assault. In some societies raids and warfare are a part of life, such as with the Norse and Saxons. The looting & pillaging that takes place leads to their victims suffering from this. Other times, sieges, or attacks by certain species like the Black Elves can cause it too. Violence can one on one which it just as traumatic, and can be caused by sexual assault, being physically attacked, or tortured for example.
Sometimes medical care can be quite brutal during this period. Without the knowledge of germ theory diseases can still be easily got causing even more damaging effects, even death so can lead to traumatic feelings. Also, no aesthetic was available at this time, and what there is usually involves trying to deal with pain with the likes of opium, being knocked out, getting the patient drunk, or suffering through operations. This has an effect on the emotional & mental wellbeing of a patient, as well as having to maybe loosing digits, limbs, or other body parts. Certainly when it comes to accidents it follows the same pattern, and has a similar effect.
The patient with PTSD relives the trauma from before on a regular basis. This affects their ability to cope, leading to problems sleeping, depression, potential outbursts of violence, hypervigilance, avoidance of situations that reminds the person of the previous, negative flashbacks & intrusive memories. Most like this in the 9th Century would be kept at the edges of society, and maybe cared for by monks & priests.

Type

Mental