According to Baby Center, toddlers hit themselves in the head as an act of frustration, self-punishment or both. Toddlers are not always able to express their anger, so they often turn violent in an attempt to do so.
Child Psychologist Penelope Leach from Baby Center warns that a toddler hitting their head may be a warning sign that they have been punished this way by an adult. In other cases, self-hitting can be an extreme act of frustration in an attempt to find an outlet that a typical tantrum does not provide for them.
Zero to Three explains that determining the exact cause of the self-hitting behavior is essential before a parent begins to take action to stop the potentially destructive behavior. Some children hit themselves as a way of acting out their guilt or shame, which can be triggered by a major life event such as becoming an older sibling or losing someone close. Parents can address the self-hitting behavior by acknowledging the feelings behind it and validating that the child is not wrong for feeling the way they feel. Encouraging the child to vocalize their distress is another tactic doctors recommend to ease the frustration behind self-hitting behavior.