Chronic exposure to stress can change personality and may even influence moral behaviour. Both chronic stress and depression alter the structure of our brains with ‘shrinkage’ in parts of the hippocampus and prefrontal cortex. The prefrontal cortex acts like a ‘logical’ brain. It modulates our emotional responses, engages in problem solving and is active during rational thought.
There is a specific part of the prefrontal cortex that makes decisions regarding behaviour. Impulsivity and the tendency for rash and risky behaviour is inversely associated with the size of this region.   Chronic stress can lead to depression and some cases of depression may be associated with this region being small.  If stress does indeed reduce the size of this region, then this may explain how stress could lead to risky behaviour and impulsivity.
Brain cells 'speak' to each other with the help of ‘messenger chemicals’ known as ‘neurotransmitters’. One such neurotransmitter is ‘Serotonin’. Although the relationship between serotonin and depression is complex, anti-depressant medication raises levels of serotonin, implying that serotonin availability is defective in depression.  We are gradually discovering that chronic stress may also be depleting serotonin levels, at least in some cases.  
A rather striking study published earlier this year demonstrated how raising serotonin levels in healthy individuals made them more reluctant to put others and themselves through harm when tempted with a cash reward. The effect was found to be dose-dependent. This remarkable finding shows how serotonin levels can influence moral judgment since the tendency to avoid putting others through harm can be equated to kindness and empathy.
We need more studies to see exactly how this dynamic would translate into the context of chronic stress, but if serotonin levels were to become ‘imbalanced’ through chronic stress as some studies seem to suggest, then this imbalance has the potential to affect a person’s morality, empathy and even personality. 
Our emotional network is restrained by parts of the ‘rational’ prefrontal cortex when we try to suppress negative emotions.   Our ability to do this diminishes with chronic stress, making us more anxious and increasing the tendency to dwell on negative thoughts and emotions.  This adds yet another negative dimension to the way in which we behave and how we perceive the world. We become more likely to register any negativity around us and may tend towards interpreting things more negatively.
If the results of all of these studies are confirmed, then chronic stress could potentially be making us aggressive, fearful, anxious, impulsive, rash and unkind progressively, over a long period of time. Some work sectors are notorious for levels of stress and it is perhaps no coincidence that workers in these sectors are seen as being impulsive, aggressive and lacking in empathy. It seems plausible that this behaviour is simply a reflection of the levels of stress they experience and the cumulative effect of this stress on the brain.
Correcting these changes in the brain could potentially reverse negative traits and negative behaviour in large sectors of the population all over the world. Burnout and stress is rife in the corporate, medical and military sectors and these negative character shifts could be affecting productivity, critical decision making, team-building as well as general workplace 'happiness'. Highly stressful jobs are often blamed for marital disharmony and a breakdown in relationships and correcting the effects of chronic stress could offer protection against such fallout. The implications of this could be immense - just think of diplomacy and world peace!
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