Mental arousal that the individual may find enjoyable or unpleasant. The three components are subjective, physiological and behavioural. The instinctive fear and flight response in animals comprises physiological reaction – raised heart rate, pallor and sweating – to an unpleasant event or stimulus. The loving relationship between mother and child is another well-recognised emotional event. If this emotional bond is absent or inadequate, the child may suffer emotional deprivation, which can be the trigger for behavioural problems ranging from attention-craving to aggression. Emotional problems are common in human society, covering a wide spectrum of psychological disturbances. Upbringing, relationships or psychiatric illnesses such as anxiety and DEPRESSION may all contribute to the development of emotional problems (see MENTAL ILLNESS).