Inattention is the lack of focus when focus on a given event or situation is required. Inattention is a hallmark feature of attention deficit-hyperactivity disorder (ADHD), which can affect adults as well as children and teens. Inattention in ADHD is often accompanied by symptoms such as restlessness, problems doing quiet activities, problems with executive function, talking excessively, and fidgeting. Inattention can also occur due to external factors such as distractions as well as situations of emotional stress, anxiety, conflict, anger, or other mood changes. Inattention can also be related to medical problems that interfere with an individual's cognitive function, such as stroke or dementia. Inattention can be seen in typical young children and is classified as a disorder only when present to excess and accompanied by problems with normal function. Depression and related conditions can cause mood changes that may include lack of attention and interest in normal daily activities.