Stress is part of everyday life for everyone…we all have disappointments, make our mistakes, and endure daily mishaps. Perhaps you lost your keys today and it made you late for work…maybe you let a friend down and are now feeling guilty about it…or maybe you are just experiencing a lot of pressure and deadlines at work. We neutralize these stressors by instituting our coping skills and relying on our natural support network. However, the overall goal is not to get rid of stress entirely, as stress is needed in healthy amounts to help us grow, develop, and learn new skills. Stress also helps us to perform optimally, as just the right amount of stress will push us to do better, such as preparing to take an exam, or preparing for a competition.
However, when you experience chronic stress (such as ongoing financial difficulties, caring for sick relatives, custody battles with your ex-spouse over the kids) or when you have major life setbacks (such as a loved one dying, relationship breakup, divorce, being fired from your job), then your ability to cope with these chronic and severe stressors may not be enough to neutralize them. So the stressors overwhelm your coping abilities: either the stressor is so severe, or your coping skills are maladaptive, or both. This can lead to adjustment problems, and you may develop an adjustment disorder. Adjustment disorder can occur when you have stressors and you are not able to cope. With adjustment disorder, you present with either anxiety symptoms, depressive symptoms, or both. Adjustment disorder seems to be a precursor to developing a full-blown anxiety disorder or depressive disorder. If the stressors are not neutralized adequately through more adaptive coping or increased natural supports, then you may go on to develop anxiety and/or depression.
Chronic stress and major life setbacks can lead to anxiety in some people and depression in others. However, in another subset of people, both anxiety and depression can occur. So the question is, how does chronic stress lead to anxiety or depression? According to the stress-diathesis model, when enough stressors combined with genetic vulnerabilities, it can lead to the development of mental disorders such as anxiety and depression (Monroe and Simons, 1991; Reinelt et al., 2013). What’s interesting is that the literature does not try to differentiate when stressors lead to either anxiety versus depression. What’s difficult about differentiating anxiety from depression is that they are highly comorbid with each other (they co-occur often) and they share many symptoms with each other. For instance both anxiety and depression are associated with the following symptoms: fatigue, poor concentration, sleep problems, muscle tension/pain, and irritability. Not surprisingly, the treatments for anxiety and depression are similar, as they are both treated with cognitive behavioral therapy (CBT) and antidepressant medications. So making further determinations if the chronic stressors transform into either anxiety or depression really does not matter that much, as the treatments for both are virtually the same.
In my clinical experience, either the patients handle the stressors with adaptive coping skills, or they don’t handle the stressors due to maladaptive coping. These are the patients that may go on to develop adjustment disorder, with the specifiers for adjustment disorder including the following: -with anxiety; -with depressed mood; and -with anxiety and depressed mood. If the stressors continue while in the midst of an adjustment disorder, then either an anxiety disorder or major depressive disorder may develop. So from clinical experience, what determines transformation into anxiety disorder or major depressive disorder? The answer might be obtained from CBT theory, as it is the person’s thoughts and appraisals about the stressors and fearful stimuli which seem to be the most important factor which determines the emergence of either anxiety or depression.
It does appear that anxiety and depression also share the same neurobiology. It starts with genetic vulnerabilities (family history) interacting with environmental triggers (life stressors), and this interaction leads to abnormal brain processing circuits, which in this case manifests as increased reactivity of the amygdala to stressors and fearful stimuli. This hypothesis has been supported by a recent study by Swartz and colleagues (2015), where study subjects with increased reactivity of their amygdala to fearful stimuli (measured on fMRI), when combined with a major life stressor, are at increased risk of developing either anxiety or depression up to 4 years later.
So if anxiety and depression share the same neurobiology and are triggered by major life stressors, then the remaining variables which determine which disorder emerges are thoughts and appraisals about the stressors, and the behavioral reaction that occurs in response to the feelings (anxious or depressed) induced by those thoughts and appraisals.
I hypothesize that the thoughts and appraisals of the stressors differentiates anxiety from depression, and that the behaviors (in response to the feelings triggered by the thoughts) maintain the negative, vicious cycle of anxiety or depression. When an individual anticipates failure or believes something bad will occur, anxiety sets in. Thus, there is a fear of not being able to act effectively, and the individual avoids the feared stimulus, which then maintains the negative cycle of anxiety (see Figure 1).
Figure 1. Negative Cycle of Anxiety
When an individual thinks all is hopeless and thinks they are useless, depression sets in. Thus, they believe their actions are ineffective, and the individual has resignation and becomes passive and withdrawn, which then maintains the negative cycle of depression (see Figure 2). Figure 3 summarizes how anxiety and depression emerge from chronic stress.
Figure 2. Negative Cycle of Depression
Figure 3. Emergence of Anxiety and Depression from Chronic Stressors
Future research should validate the hypothesis that thoughts and appraisals about a chronic stressor determine which disorder emerges, either anxiety or depression. A likely starting point for such research is to follow study subjects who have high reactivity of their amygdala to fearful stimuli, and who have also experienced a major life stressor. With such research, it may reveal that anxiety and depression are really just the same disorder (but different subtypes), given the shared neurobiology, similar overlapping symptoms, similar treatments, increased risk of developing the other when you have one of them, and the high co-occurrence of both disorders.
Here’s the take home message: stress, if it becomes severe and chronic, may transform into anxiety and/or depression. Therefore, it is important to deal with stress and cope with it effectively. It is not the stressor that causes anxiety or depression, but rather your thoughts about the stressor that induce anxious feelings or depressed mood. In addition, your avoidant and isolative behaviors serve to maintain the vicious, negative cycle of anxiety and depression.
Help is available for changing the way you think and behave in response to a stressor.