Can an adult discharge himself from a hospital?

Generally, yes. In most cases, adults are legally competent to make decisions about their own medical care, and they have the right to discharge themselves from a hospital. However, there are some exceptions to this rule. For example, if a person is deemed to be a danger to themselves or others, or if they are unable to make informed decisions about their own care, they may be involuntarily committed to a hospital. Additionally, some hospitals may have policies that require patients to stay for a certain period of time before they can discharge themselves. It is important to check with the hospital's policy before attempting to discharge yourself.