Once a child reaches 18, they are legally classed as an adult. This means that they will be treated as being able to make their own decisions in respect of their health and financial decisions unless it is deemed that they lack the mental capacity to do so. Their parents or legal guardians will no longer have the authority to act on their behalf. However, children with an ABI can often need more support than other children their age when making decisions regarding their health or finances, or they may not have the mental capacity to deal with these decisions at all.