What condition is most likely affecting Meredith if she suddenly screams and kicks without previous conflict?

The condition most likely affecting Meredith, given her sudden screaming and kicking without prior conflict, is dementia. Individuals with dementia may experience sudden outbursts or changes in behavior, often referred to as "sundowning" when symptoms worsen in the late afternoon or evening. These outbursts can be triggered by confusion, frustration, or misinterpretation of their environment, which can occur without any apparent provocation.

In contrast, while anxiety disorders might lead to feelings of panic or distress, the behavior observed in Meredith is more indicative of dementia's impact on cognitive function and impulse control. Medications might also alter behavior, but if she was previously stable, it would be less likely that a sudden reaction stems solely from her medication regimen. Lastly, while hospital stress can indeed affect behavior, the specific nature of Meredith's reaction aligns more closely with symptoms of dementia, which is characterized by progressive brain function decline affecting behavior and emotional regulation.