are mild and do not cause permanent or long-term disability; however, all severity levels of TBI have the potential to cause significant, long-lasting disability. Permanent disability is thought to occur in 10% of mild injuries, 66% of moderate injuries, and 100% of severe injuries. Most mild TBI is completely resolved within three weeks. Almost all people with mild TBI are able to live independently and return to the jobs they had before the injury, although a small portion have mild cognitive and social impairments. Over 90% of people with moderate TBI are able to live independently, although some require assistance in areas such as physical abilities, employment, and financial managing. Most people with severe closed head injury either die or recover enough to live independently; middle ground is less common. Coma, as it is closely related to severity, is a strong predictor of poor outcome. Prognosis differs depending on the severity and location of the lesion, and access to immediate, specialised acute management. Subarachnoid hemorrhage approximately doubles mortality. Subdural hematoma is associated with worse outcome and increased mortality, while people with epidural hematoma are expected to have a good outcome if they receive surgery quickly. Diffuse axonal injury may be associated with coma when severe, and poor outcome. Following the acute stage, prognosis is strongly influenced by the patient's involvement in activity that promote recovery, which for most patients requires access to a specialised, intensive rehabilitation service. The Functional Independence Measure is a way to track progress and degree of independence throughout rehabilitation. Medical complications are associated with a bad prognosis. Examples of such complications include: hypotension (low blood pressure), hypoxia (low blood oxygen saturation), lower cerebral perfusion pressures, and longer times spent with high intracranial pressures. Patient characteristics also influence prognosis. Examples of factors thought to worsen it include: abuse of substances such as illicit drugs and alcohol and age over sixty or under two years (in children, younger age at time of injury may be associated with a slower recovery of some abilities). Other influences that may affect recovery include pre-injury intellectual ability, coping strategies, personality traits, family environment, social support systems and financial circumstances. Life satisfaction has been known to decrease for individuals with TBI immediately following the trauma, but evidence has shown that life roles, age, and depressive symptoms influence the trajectory of life satisfaction as time passes. Many people with traumatic brain injuries have poor