Stressful and traumatic events or thoughts cause the release of hormones called cortisol (stress) and norepinephrine (anxiety, heart rate increase) which weaken the immune system and dramatically slow the growth (or destroy neuronal cells) of many parts of the limbic system (the unconscious part of the brain that regulates emotion, memory, behavior, etc..) including the amygdala (which is the main actor in social behavior, emotional and impulse control along with the activation of the fight-flight-freeze response system), the hippocampus (which turns short-term memory into long-term memory through neurogenesis), hypothalamus (which releases endocrine hormones that affect body temperature, hunger, thirst, fatigue, sleep, and circadian cycles) and the prefrontal cortex, including the areas included in the empathic pathways of the brain such as the inferior frontal gyrus (emotional empathy), ventromedial prefrontal cortex (cognitive empathy) or uncinate fasciculus (which connect the frontal cortices to the limbic system). (LeDoux, 1996. Siegel, 2004. Shamay-Tsoory, 2011. Baron-Cohen, 2011). It appears that this damage happens when cortisol triggers the release of an excessive quantity of the excitotoxic neurotransmitter named "glutamate". (Perry, 2011)

The main idea here is that due to the constant stress many people have endured in early life, some areas of their brain are underdeveloped (and some overdeveloped to compensate) while the adrenal glands (which control the release of cortisol) or its interaction with the amygdala and the hippocampus may be unregulated (LeDoux, 1996). This is, in my opinion, the primary cause of personality disorders, some types of depression and of complex post-traumatic stress disorder. One important thing to note is that these pathologies have very little or no impact on motor skills, intelligence or other general functions such as sensory processing. In other words, someone with a stress-related disorder is usually in no way "dumber" than the average unstressed person; they simply can't control emotion or behavior as effectively.

Thankfully, most of the damage caused by excessive stress or trauma can be reversed. It has been scientifically proven that learning about emotions and psychological concepts develops your prefrontal cortex - which allows logic to control emotion by connecting your cortex to the limbic system - through neuroplasticity (Perry, 2011. Doidge, 2007. LeDoux, 1996). Love, on the other hand, allows for the synaptic pruning (death) of unwanted neurons through the release of the neuromodulators (substances that control neurotransmitters) named oxytocin and vasopressin (Doidge, 2008). In a way, love appears to be the only way to completely get rid of most mental disorders resulting from trauma, as it is the only way to get rid of unhealthy synaptic connections. As far as medication goes, some SSRI antidepressants temporarily increase neurogenesis in the hippocampus which is one of the most important aspects of recovery (Doidge, 2007). This is believed to be the reason many antidepressants require 3 to 6 weeks before reaching full efficacy (Doidge, 2007). Endorphins are also important in recovery, as they counteract the effects of cortisol and are the pillars of happiness and well-being. (Beck, 1988. Perry, 2007, Perry, 2011)