Major depressive disorder, or MDD, is a serious mental health condition centered on one’s emotional well-being. With a great deal of research dedicated to understanding this pervasive disorder, a number of risk factors and correlations have been discovered, shedding light on attributions and circumstances that can, in some cases, act as causes for depression.
According to the American Psychiatric Association (APA), the key symptoms of depression are a sense of deep and pervasive despair, low mood, and irritability. Additional symptoms include hopelessness, an inability to experience happiness, and a difficulty concentrating.
Depression appears across races and cultural backgrounds, age groups and genders, with the World Health Organization (WHO) finding that over 264 million individuals around the world contend with this disorder. The APA has additionally found that 17.3 million (or 7.1%) of the US adult population will reportedly experience one or more depressive episodes across their lifetime.
The WHO also cites depression as a leading cause for disability, as it can negatively affect one’s capacity to function, causing them to suffer both emotionally and in different aspects of their lives, such as work productivity, academic studies, and family life.
The latest edition of the APA’s Diagnostic and Statistical Manual’s fifth edition (the DSM-V) lists several factors that can, in certain cases, bring about major depression:
A number of physical factors have been discovered in correlation with depression:
Exposure to adverse life events during childhood, and particularly intense trauma of varying types, has been shown to be related to the appearance of depression. The instability that such experience introduces into the child’s life is thought to influence their susceptibility to developing depression later on in life.
While cultural differences have presently not been found to affect the appearance of depression, a direct and strong correlation between depression and gender has been repeatedly proven.
The APA’s findings reflect this, stating that women are 1.5-3x more likely to develop major depression than men. This difference in gender-based prevalence becomes apparent around the age of ten, and continues until middle age, when women and men once again exhibit similar rates of depression.
A temperamental factor has also been found to be related to the appearance of depression. Neuroticism—the inclination to react negatively to sources of anxiety and stress—can cause an individual to remain focused on an adverse experience, and to intensify their response to it. Their resulting outlook on life may be apprehensive and pessimistic, negatively affecting their well-being. Low neuroticism has been linked to resilience in the face of adversity, while high neuroticism has been linked to a proneness to depression.
The existence of additional, non-mood disorders has also been tied to depression. It has also been linked to the sustainability of depression: specifically, depression tends to be more stubborn, or treatment-resistant, when appearing together with another serious disorder.
The three most common mental health disorders to appear with depression are:
Chronic or disabling physical health conditions have also been shown to increase the risk of developing depression. In such cases, depression and the existing physical disorder tend to exacerbate each other’s severity.
Among the physical conditions found to be related to increased rates of depression are:
Already dealing with an existing, adverse condition, such as the ones mentioned above, has been shown to act as a backdrop that helps facilitate the eventual appearance of depressive symptoms.
It is important to note that while the correlation between these factors and depression has been substantiated, the causation—affirming that a certain factor is what causes depression, and not the other way around—has been less clearly defined.
As such, it is important to consider the three conditions for causality, which necessitates that all three exist in order for causation to be established:
Depression is often an overwhelming experience, which can catch the individual experiencing it off-guard, and leave them feeling isolated and alone. But this does not have to be the case: these days, there are many depression treatment options that have been researched and recognized by the FDA for their proven safety and efficacy. Such treatments include antidepressant medication, psychotherapy, and transcranial magnetic stimulation.