Depression is a complex and multi-faceted sickness, which is often interwoven with other conditions. It's not always clear which work as causes and which work as effects, being more likely they build up on one another dynamically over time. In any case, when another condition manifests co-morbidly with depression, it will often require an additional course of treatment.
For the sake of reference, this article will overview four of the most common conditions that tend to co-exist with depression. Generally speaking, both depression and its associated conditions will diminish and fade out gradually, provided the right therapies are embraced. Conversely, focusing just on treating depression will not be too effective if other concurrent issues are left undiagnosed and untreated.
By far and wide, the most common issue that manifests with depression is anxiety disorder, with both conditions often going and in hand and reinforcing one another. In fact, as many as 50% of patients suffering from depression also suffer from anxiety disorder, and vice-versa. This is quite a catastrophic combo, that can be equated to a feverish state comprised of hot flashes and cold chills... except it takes place in your mind and could go on and on for decades.
Another highly common issue that develops in patients suffering from depression, and often one that leads up to chronic depression, is substance abuse. Whether the substance in cause is alcohol, illegal drugs or pharmaceutical drugs, patients suffering from abuse problems will find it nearly impossible to manage their depressive moods until they've received treatment to keep their substance abuse problems in check.
Other medical issues
In many cases, depression can either be the cause or the effect of an undetected physical sickness - anything from heart disease to cancer or hypothyroidism. In this case, the underlying disease can make it particularly difficult (or even unlikely) to manage depression, unless it's also addressed its own treatment The opposite is also quite common: people struggling with serious medical conditions often have undiagnosed depression, which when treated will also make it easier for the patient to overcome the associated medical condition more easily.
The bottom line: people suffering from depression should get thorough medical exams to determine whether there may be an underlying physical condition working together with depression. People suffering from serious physical sicknesses should see a therapist to be analyzed for the possibility clinical depression; in fact, it looks like the boundaries between physical and mental sickness often are blurred, and in the future the work of medical doctors and psychologists should evolve to become more collaborative and adaptive to one another.