Within the human body, stress is defined as a homeostatic state that is threatened by either intrinsic or extrinsic adverse factors. These are frequently counterbalanced with a collection of physiological and behavioral responses which aim to establish the optimal body equilibrium or eustasis. An adaptive stress response is dependent on the extremely interconnected neuroendocrine, molecular, and cellular infrastructure which makes up the stress system. Other key components include vital spots in the central nervous system, the hypothalamic-pituitary gland axis, and the autonomic nervous system. Thus, negative as well as positive emotions have an impact on the autonomic nervous system and, by extension, some effect on adaptive responses.
Though current research has no exact conclusion on the influence of emotions on adaptive responses, a number of researchers have analyzed the expression of emotions on the acquisition and prevention of certain medical conditions. For instance, the research on psychological risk factors for cardiovascular and related health issues has come up with a correlation between the conditions and negative emotions such as anger, anxiety, depression, and distress. These studies explored these emotions in two dimensions, valence, which defines a level of pleasantness, and arousal, which is responsible for the intensity of the measured emotion. Additionally, a continuously increasing body of scientific literature suggests that psychological states and traits that are influenced by positive emotion are connected to the reduced risk of clinical cardiovascular disease. On the other hand, there has been evidence that has suggested that acute positive emotions, such as happiness or excitement, can trigger acute coronary syndromes.
As such, there is a possibility that emotion-driven differential autonomic nervous responses have an effect on diverse cardiovascular outcomes of negative and positive emotions. A multitude of factors can be used to assess this hypothesis. For instance, while the autonomic nervous system is essential in determining the arousal component of emotion, brain activity can suggest the valence of the emotion. Brain circuits do not have identical responses aversive, causing negative emotions and appetitive, inducing positive emotions, environmental cues, or memories.
A study that introduced these assessments to their experimentation concluded that positive emotions caused by the recollection of the moments of happiness, and negative emotions induced by anger recall, resulted in differential autonomic nervous system responses. They also revealed that the participants who had anticipated feelings of happiness showed an increase in parasympathetic activity. This can suggest that the adaptive responses are not only affected by adverse or positive emotions but by the hypothetical states of either as well.
When assessing brain activity alongside the autonomic nervous system, the study found that the participants with paradoxical right frontal lobe activity shifted towards parasympathetic and sympathetic autonomic nervous system activation during happiness recall. Incongruent moods and electrocortical responses may be related to stable psychological characteristics such as hostility and contextual psychological factors such as trait anger, depression, and anxiety. This can suggest that recurring emotions of both positive and negative nature may be the cause of retained adaptive responses that are manifested through psychological and behavioral contexts.
From a more behavioral perspective, the effects of the autonomic nervous system and the stressful stimuli induce emotions that are able to interrupt ongoing activity. This can be seen in individuals feeling disgusted, who are driven to stop any continuous action and remove themselves from the stress component. This can be observed as an outcome of the autonomic nervous system that heralds emotions as adaptive devices. On a chemical scale, this occurs when patterned activation within the autonomic nervous system that is affected triggers the autonomic nervous systems of other biological systems such as motor programs, facial expressions, and vocalization. This activation results in cohesive and specific physical responses that others perceive as emotions.
The purpose of emotions as adaptive devices is not fully proven but was highly supported by the evidence found within physiological, biological, and autonomic nervous system responses to adverse environmental cues. The adaptive component of emotion becomes not only visible within specific psychological outcomes and elevation in activity within nervous systems but also in long-term traits that can be found within behavioral responses. Additionally, the role of the autonomic nervous system within the adaptive purpose of emotions is not entirely researched and documented. It is likely that in the coming years, more will be uncovered about the biological factors that influence emotions and adaptability.