Couch, Lipton, Stewart and Scher (2007) argue that headaches, one of the hallmarks of PCS, occur in a variety of injuries to the head and neck. Further, Lew et al. (2006) reviewed ample studies comparing headaches to post-traumatic headaches and found that there is wide heterogeneity in the source and causes of headaches. They point out that the International Headache Society lists 14 known causes of headaches, as well. Furthermore, the headaches may be better accounted for by mechanical causes, such as whiplash, which is often mistaken for PCS. An additional possibility is that posttraumatic stress disorder can account for some cases diagnosed as PCS, but for emotional regulation as well.Depression, posttraumatic stress disorder, and chronic pain share symptoms resembling those of PCS. One study found that while people with chronic pain without TBI do report many symptoms similar to those of post-concussion syndrome, they report fewer symptoms related to memory, slowed thinking, and sensitivity to noise and light than people with mTBI do. Additionally, it has been found that neuroendocrinology may account for depressive symptoms and stress management due to irregularities in cortisol regulation, and thyroid hormone regulation. Lastly, there is evidence that major depression following TBI is quite common, but may be better accounted for with a diagnosis of dysexecutive syndrome.In a syndrome, a set of symptoms is consistently present, and symptoms are linked such that the presence of one symptom suggests that of others.
It is frequently stated in the literature and considered to be common knowledge that 15–30% of people with PCS have not recovered by a year after the injury, but this estimate is imprecise because it is based on studies of people admitted to a hospital, the methodologies of which have been criticized. In approximately 15% of people, symptoms may persist for years or be permanent. If symptoms are not resolved by one year, they are likely to be permanent, though improvements may occur after even two or three years, or may suddenly occur after a long time without much improvement. Older people and those who have previously had another head injury are likely to take longer to recover.The way in which children cope with the injury after it occurs may have more of an impact than factors that existed prior to the injury. Childrens mechanisms for dealing with their injuries may have an effect on the duration of symptoms, and parents who do not deal effectively with anxiety about childrens post-injury functioning may be less able to help their children recover.If another blow to the head occurs after a concussion but before its symptoms have gone away, there is a slight risk of developing the serious second-impact syndrome (SIS). In SIS, the brain rapidly swells, greatly increasing intracranial pressure.