Stress and Neural Wreckage

Crash Course on Stress

Our bod­ies are a com­plex bal­anc­ing act between sys­tems work­ing full time to keep us alive and well. This bal­anc­ing act is con­stantly adapt­ing to the myr­iad of changes occur­ring every sec­ond within our­selves and our envi­ron­ments. When it gets dark our pupils dilate, when we get hot we sweat, when we smell food we sali­vate, and so forth. This con­stant adaption main­tains a range of sta­bil­ity in the body and is often referred to as allosta­sis. Any change which threat­ens this bal­ance can be referred to as allo­sta­tic load AKA stress.

Allo­sta­tic load/stress is part of being alive. For exam­ple just by get­ting up in the morn­ing, we all expe­ri­ence a very impor­tant need to increase our heart rate and blood pres­sure in order to feed our newly ele­vated brain. Although usu­ally man­age­able, this is a change which the body needs to adapt to and, by our def­i­n­i­tion, a source of stress.

Stress is only a prob­lem when this allo­sta­tic load becomes over­load. When change is exces­sive or our abil­ity to adapt is com­pro­mised, things start to go wrong.

Energy Mobi­liza­tion

Whether it’s get­ting up in the morn­ing, wor­ry­ing about the non-existent past/future, or cussing out your computer, stress takes energy. The body mobilizes energy via the infa­mous fight or flight response. If you need to run away from a swarm of killer bees or fend off an attack­ing bear, you will be assisted by var­i­ous chem­i­cals pro­duced within the body. These include the well-known adrenaline–now more com­monly referred to as epinephrine–and a lesser known group of chem­i­cals known as the glu­co­cor­ti­coids, most notably cor­ti­sol. Both epi­neph­rine and the glu­co­cor­ti­coids are involved in mak­ing stored energy avail­able for use in the form of fats and sug­ars. Epi­neph­rine does so over the short term (within sec­onds) while cortisol acts over a longer period (min­utes to hours). Let’s look at the effects of the later of the two, cortisol.

Your Brain on Stress

Cor­ti­sol does an excel­lent job of allow­ing us to adapt to most stres­sors which last more than a cou­ple of min­utes but under an hour. Short term it will enhance our immune sys­tem, mem­ory and and ability to focus. Long term, past 20 minutes to an hour, cortisol causes brain damage. It seems we were designed more to deal with short spurts of high stress, such as beat­ing back that attack­ing bear, rather than long drawn-out stres­sors such as meet­ing deadlines.

Our brains are most vul­ner­a­ble to the effects of exces­sive stress in a region called the hip­pocam­pus. The hip­pocam­pus is a mass of neu­rons impor­tant for deal­ing with emo­tions and con­sol­i­dat­ing new mem­o­ries. As with all brain regions, its abil­ity to adapt relies upon being able to alter the branch­ing and con­nec­tions of its brain cells. Fortunately the hip­pocam­pus is also one of the only regions of the brain known to be able to pro­duce new neu­rons under certain conditions, a process called neurogenesis.

Brain Dam­age

Endur­ing a high stres­sor for more than 30 min­utes to an hour has been shown to neg­a­tively impact the hip­pocam­pus in var­i­ous ways. Sus­tained expo­sure to cor­ti­sol results in the prun­ing back of the num­ber con­nec­tions of hip­pocam­pal neu­rons and increases the rate of brain cell death.

As if this wasn’t bad enough, recent research is also demon­strates that sus­tained high cortisol lev­els also impair­s the hippocampus’s abil­ity to cre­ate new neurons.

Over a period of time, all of this results in the shrink­ing in size of the hip­pocam­pus with asso­ci­ated declines in brain func­tion, includ­ing the abil­ity to retain new infor­ma­tion and adapt to novel situations.

Dam­age Control

For­tu­nately the neg­a­tive effects of exces­sive stress can not only be stopped but also reversed once the source (psy­cho­log­i­cal or phys­i­cal) is removed or suf­fi­ciently reduced. Look for future posts outlining ways to both pro­tect and renew our brains by man­ag­ing the unavoid­able stres­sors we all face as part of being human.