There is no doubt that a relationship exists between stress and depression. From researchers studying the genetics of stress and depression to experts at the National Alliance on Mental Illness and the American Institute of Stress, there is widespread agreement that stress is linked to depression. However, the extent to which one impacts the other varies significantly in each person.
Stress
Stress is a normal physiological response to external pressures, situations and illness. When we face stress, our body prepares to deal with the challenge by releasing chemicals (the stress hormone cortisol, adrenalin and neurotransmitters) that give us extra energy and affect all our critical organs.
Depression
Depression results from an imbalance of neurotransmitters, but it can be caused by a variety of factors, including genetics, the environment, illness, substance abuse or any combination of factors. Major depression is defined as low energy, loss of interest and changes in appetite, weight, sleep and cognitive abilities that last at least two weeks.
Similarities
Stress and depression can both be caused by life events and medical conditions. The one difference is that stress can be caused by pleasant events such as a promotion or marriage, while depression is associated with unwelcome events like financial difficulties or death. Stress and depression share some similar behavioral symptoms, including social isolation, increased or decreased eating, sleep disturbances and potential drug abuse. Facing repeated stress and the negative mindset of depression can result in feelings of helplessness.
Relationship
A cause-and-effect relationship exists between stress and depression. Struggling with unrelenting stress increases the potential for depression. On the flip side, depression lowers the ability to cope, and any small daily challenge may trigger unusually high stress. Ongoing stress results in continuously elevated levels of biochemicals, and that leads to medical conditions, including depression. Physicians at the University of Maryland Medical Center (UMMC) state, "Some evidence suggests that repeated release of stress hormones...disrupts normal levels of serotonin, the brain chemical that is critical for feelings of well-being." In their overview of research published in January 2009 on the website PLoS ONE, Alessandro Bartolomucci and Rosario Leopardi discussed a potential subtype of depression called stress-induced depression, stating that the link between stress and depression can be deeper than previously recognized.
Genetic Studies
In the July 2003 issue of Science, Avshalom Caspi et al. reported that a "short" version of a serotonin transporter gene doubled the risk of depression as a result of stressful life events. They also discovered that people who lived through stressful life events but who had a "long" version of the gene experienced no more depression than people who were spared from the same stressful life events.
