In human and non-human animals the steroid hormones cortisol and testosterone are involved in social aggression and recent studies suggest that these steroids might jointly regulate this behavior.
Most important in this regard is the male sex hormone testosterone, which is associated with increased aggression in both animals and in humans. Research conducted on a variety of animals has found a strong correlation between levels of testosterone and aggression.
Physical effects of anger
The adrenal glands flood the body with stress hormones, such as adrenaline and cortisol.
In the last decade, data from both animal and human studies have been suggested that serotonin has more associated with impulsive aggression than with aggression subtypes, with more “waiting impulsivity” in impulsivity subtypes.
Dopamine hyperactivity in brain regions linked to reward-related motivation, such as the nucleus accumbens (NCC) and prefrontal cortex, also leads to increases in impulsive and aggressive behavior (see reviews by Everitt & Robbins, 2000; Friedel, 2004).
Specific neurotransmitter systems involved in mammalian aggression include serotonin, dopamine, norepinephrine, GABA, and neuropeptides such as vasopressin and oxytocin.
Cortisol is a steroid and the body's main stress hormone, released from the adrenal cortex. One of the first studies described a model in which the HPA axis was linked to aggression (47) and later, cortisol and aggression were seen in wrestlers who after fighting showed an increased level in serum cortisol (48).
The findings suggest that when serotonin levels are low, it may be more difficult for the prefrontal cortex to control emotional responses to anger that are generated within the amygdala. Using a personality questionnaire, they also determined which individuals have a natural tendency to behave aggressively.
Serotonin is associated with happiness, focus and calmness. Dopamine is associated with rewards and motivation. Dopamine and serotonin also share involvement in some mental health conditions, including depression and mood disorders.
Too much serotonin, however, could result in serotonin syndrome, which could lead to symptoms of restlessness, hallucinations, and confusion. Serotonin is also known as a hormone within the enteric nervous system of the body, primarily found within the gastrointestinal tract (gut).
Serotonin is a mood regulator and happiness booster. When your body produces less estrogen, your emotions may feel off-balance. Your emotions should stabilize after your body adjusts to the decrease in estrogen. You may find that your feelings of rage are touch and go.
Estrogens have important effects on aggressive behavior, as well as other related social behaviors such as copulation and communication.
The causes behind aggressive behavior can include (but are not limited to): Fear, anxiety, stress. Unmet physical needs (hunger, silence) or emotional needs (recognition, love) Traumatic experiences.
Oxytocin promotes aggression in response to provocation in low anxiety people. Oxytocin does not elicit aggression after no provocation or in high anxiety people. Thus, oxytocin is conditionally involved in the creation of aggressive behavior. Situational and dispositional features are essential to predict its effects.
Serotonin also regulates the pre-frontal cortex; therefore, lower levels of serotonin affect our response to external stimuli, meaning the person becomes aggressive easily and can't control their responses in a 'normal' way. They can't anticipate risk and therefore impulsively engage in aggressive behaviour.
Scientists believe that dopamine is responsible for us repeating behaviors or activities that are pleasurable. Low levels of dopamine are linked to depression and schizophrenia. High levels are linked to attention deficit hyperactivity disorder (ADHD), binge eating, and addiction.
In both primates and humans, serotonin function tends to covary positively with prosocial behaviors such as grooming, cooperation, and affiliation, and tends to covary negatively with antisocial behaviors such as aggression and social isolation.
Although direct stimulation of GABA receptors generally suppresses aggression, a number of studies have found that positive allosteric modulators of GABAA receptors can cause increases in aggressive behavior.
Under some circumstances, oxytocin may increase aggression by enhancing reactivity to provocation and simultaneously lowering perceptions of danger that normally inhibit many women from retaliating. There is some evidence that high levels of estradiol and progesterone are associated with low levels of aggression.
Results Low cortisol levels were associated with persistence and early onset of aggression, particularly when measures of cortisol concentrations were pooled.
A greater increase in cortisol is linked to a greater increase in levels of aggressive behaviour, while a greater increase in estradiol corresponds to a decrease in levels of aggressive behaviour," adds Pascual-Sagastizabal.
The brain chemical serotonin has long been known to play an important role in regulating anger and aggression. Low cerebrospinal fluid concentrations of serotonin have even been cited as both a marker and predictor of aggressive behavior.
Aggression also depends on environmental context (such as scarcity of resources), social necessity (for status or to defend territory) and gender. Not surprisingly, males tend to be more physically aggressive than females. The etiology of neurobiological impairments in the aggressive population requires further study.
Other factors which can be causes of violence include:
Having low self-worth. Experiencing abuse or neglect. Witnessing violence in the home, community, or medias. Access to weapons.
There is some evidence that high levels of estradiol and progesterone are associated with low levels of aggression.