Depression and anxiety can occur in the absence of any medical condition, and indeed, frequently do. But a number of medical disorders can cause depression in and of themselves, and treatment should be aimed at eradicating the underlying disorder as opposed to treating the resulting depression.
Among the more common hormonal problems associated with depression is a dysfunctional thyroid leading to hypothyroidism or low thyroid levels. Other hormonal abnormalities causing depression as well as occasional mania is a serious condition called Cushing's disease, while systemic lupus erythematosis, an autoimmune disorder, can cause a number of psychiatric symptoms as well.
Diseases associated with an aging population, notably Alzheimer's and Parkinson's disease, are commonly linked to depression, as are congestive heart failure, anemia and even infectious diseases.
Depression following stroke also affects up to 30% of stroke victims.
People who must live with chronic pain may have good reason to be unhappy, although not all chronic pain sufferers, somewhat remarkably, are unhappy. Conversely, pain is sometimes recognized as a symptom of depression, while pain from any medical condition can also make existing depression worse.
Whether from chronic pain or any other medical illness, depression is not a normal consequence of illness or injury even if the person "has a good reason to be depressed". Regardless of the context, a person may be unhappy about his or her situation but unhappiness is not depression. If depression develops as a consequence of a serious medical illness, it should be treated in and of itself, whatever else the person may require.
There are also situations where an antidepressant medication, notably the tricyclic antidepressants (TCAs), are prescribed not to treat depression but to treat pain. The TCAs are particularly effective in people who have various types of nerve pain which often do not respond well to other types of analgesics. The same class of medications can be helpful for a musculoskeletal condition called fibromyalgia as well, which again does not respond well to other types of pain-relieving medications. Another link between depression and medical conditions lies in the need to use certain medications to treat that medical condition.
Some cancer drugs along with some drugs used to treat high blood pressure and other heart conditions can cause depression in some people. Corticosteroids, which are used for a wide variety of diseases including rheumatoid arthritis can make people more prone to either depression or anxiety. As well, if people are ill, the adjustments they have to make to the limitations imposed on them by their ill health can often be very difficult. A man who used to take pride in being fit and virile can't help but feel the loss of his "self-hood" if some serious medical event makes it impossible for him to be active - physically or sexually. A woman who has had a heart attack may feel chronically anxious about having a second event, as would any woman about a new lump in her breast if she's been treated for breast cancer. All these factors together make the medical ill highly vulnerable to depression and anxiety. However, it is important for people - and for their caregivers - not to assu me that depression is a "natural" consequence of someone becoming ill or having to live with chronic pain.
If people are feeling depressed, they should discuss the fact that they are feeling depressed with their doctor, and antidepressant therapy used to alleviate symptoms.
