Flooding is a loss in homeostasis in the vegetative systems, especially autonomic and endocrine, in response to a perceived threat or unfavorable event. It causes a disruption of self-regulation and self-awareness. There is a loss of connection between the prefrontal cortex and limbic centers (and through limbic centers, lower centers). Behavioral at this time cannot be unified, and is often chaotic or crudely instictual. Flooding is often coupled with the sympathetic fight or flight response. It can also be coupled with the dorsal vagal 'freeze' response but this manifestation is less recognized because the outward behavior is less disruptive.

It is a dissociative state, and memories of this time will never be clear. The subjective and behavioral manifestation of flooding are sometimes termed 'upset'. Flooding is a threshhold phenomenon. Once the threshold is reached the state cannot be quickly reversed.

Paradoxically, during flooding there is often an intense desire to fix problems but simultaneously, a catastrophic impairment of problem solving abilities. Logic is impaired. All agreement or understandings previously in place will not be operable. When flooding is recognized, all discussion, negotiation, analysis, etc... should cease because it just prolongs the state. Instead, soothing activity should begin at once. Rage is a flooded state. People, when not flooded tend not to recognize or own their actions performed a flooded state, and arguing about this tends to become a secondary red-herring that obscures basic conflicts that lead to the upset in the first place