Great question – the answer is both! Physical damage to the brain can make it harder to receive the benefits of positive activities, such as spending time with your friends. On average, people with a brain injury get less reward (managed by a chemical called dopamine in our brain) from everyday experiences. Too little dopamine can put someone at risk of depression. However, the psychological aspect is also important. Having a brain injury can be very traumatising, and coping with the sudden changes in one’s life is very stressful and can kickstart depression as well. It’s likely that the physical injuries interact with the psychological damage, which is why depression is so common after brain injury.