Acquired brain injury (ABI) is a major cause of disability and death worldwide. It refers to any damage to the brain that occurs after birth and can either be traumatic where it is caused by an external physical force involving a blow to the head or non-traumatic where it can have multiple causes including disease, infection, toxic poisoning, tumour, and substance misuse. In the case of traumatic brain injury, for example, the acceleration and deceleration of the head tends to produce more diffuse and widespread lesions throughout the brain, affecting a range of abilities that often include mental speed, attention, memory, planning, problem solving, self-awareness, and self-monitoring. In particular, this is because problems with memory and executive function can impact on a person's ability to initiate and follow through with restructuring techniques, to challenge thoughts, and generate more positive ways of thinking.