Everyone who has ever been ill knows how physical illness or pain affects mood. The relationship between depression and physical ill health seems obvious but in fact the mechanisms do vary. One way of thinking about these mechanisms is to consider whether they have a direct or an indirect effect on mood. In this Sharepost I'm going to examine just some of the relationships between physical ill health and depression.
Physical illnesses have a variety of ways of causing depression. For example, an illnesses or viral infection that affects specific areas of the brain can result in depression. Then again, if some physical illness has a direct effect on hormone producing organs that also influence brain function, mood may be affected. Physical illness can disrupt the functioning of the immune system which may result in a domino effect of neurological disruption leading to depression. Illnesses such as Parkinson's disease, multiple sclerosis, and epilepsy all damage parts of the brain that influence mood. Various studies have also indicated the strong likelihood of depression following a stroke.
When mood changes persuade people to visit their doctor one of the first things the doctor will do is take blood tests. A variety of physical conditions manifest themselves as depression and/or anxiety, so it's important to rule these out as potential causes of depression. Neurotransmitter activity, for example, is affected by diseases of hormone producing glands such as the thyroid. Over time this can affect mood and lead to depression. If cortisol secretions from the adrenal glands are affected either Cushing's disease (too much cortisol) or Addison's disease (too little cortisol) may develop along with the symptoms of depression.
Most people have, at some point, suffered with influenza. Aches, pains and a high temperature may appear the most problematic symptoms but it is rare to find someone with flu who isn't also exhibiting symptoms of depression. In and of themselves aches and high temperatures do not cause depression. What actually happens is that severe viral infections affect the immune system which in turn affects our hormonal system. As the hormonal system affects mood-regulating neurotransmitters in the brain it follows that disruption can lead to depression.
It is not uncommon to find that people who tend to get depressed have relatively ineffective immune systems, and vice versa. A rather viscous circle then arises in which depressed people become more vulnerable to infections which in turn leads to greater despondency during or just after the main symptoms of a viral infection have passed.
There are a variety of chronic diseases or conditions that may indirectly lead to depression. Just a handful of examples include rheumatism, cardiac problems, cancers or chronic respiratory problems. It is the unremitting stress, pain and discomfort of chronic conditions that contribute to depression. It would be wrong however to suggest that everyone with a chronic condition becomes depressed. People appear to be predisposed to depression and those who were never depressed prior to physical illness have a far higher chance of remaining free from depression when ill.