Some physical illnesses, particularly heart disease and other conditions that affect the blood supply, are more likely to occur in people with depression. It is not simply that physical illnesses can lead to depression, the opposite occurs too. This makes the recognition and treatment of depression all the more urgent.

Physical illnesses in which depression is common

Below are some of the more common conditions in which depression is likely to occur:

Diseases of the nervous system

• Parkinson's disease. About 40 per cent of those with Parkinson's disease will suffer from an episode of depression. It is often missed because some of the symptoms of Parkinson's disease are similar to those of depression. For example, slow movements and reduced speech occur in both depression and Parkinson's disease. It seems likely that the increased occurrence of depression in Parkinson's disease results from both the direct effects of the disease on the brain and the impact of the condition on the sufferer's everyday life.
• Dementia. People with dementia suffer from more depressive symptoms and more depressive illnesses than other people. The difficulty these people have in communicating their distress means the depression can be missed and not treated. The development of features such as a loss of interaction and interest in others and a sense of gloominess may mean that a depressive illness is developing and help should be sought.
• Multiple sclerosis. Depression is more common in this condition, too. It is not clear how much of the depression arises from the effects of the disease on the brain and how much results through the consequences of the disability.

Vascular diseases (diseases of the blood vessels)

• Heart disease. Depression is more common in people with heart disease. It is increased in those suffering from angina (chest pain triggered by thickening of the arteries), and is two to three times more common in people after a heart attack (your doctor may refer to this as a myocardial infarction or MI). Depression in such circumstances also leads to problems for people recovering from a heart attack, making them more at risk of another heart attack. In addition, they may have more difficulty returning to work and more general disability.
• Stroke. Similarly, depression is much more common in people after a stroke and is probably increased in people having 'ministrokes' too (your doctor may refer to these as transient ischaemic attacks or TIAs). Again, those who suffer depression tend to have a more severe and prolonged illness than those with no depression.
• High blood pressure (hypertension). Studies have shown this also leads to increased rates of depression.

Endocrine disorders

• Hypothyroidism. Low levels of thyroid hormones can lead to depression, which may be very severe. However, unlike the conditions mentioned above, treatment of the hypothyroidism itself (with thyroxine to replace the missing hormone) can also treat the depression.
• Cushing's syndrome. This is a rare disease caused by an excess of certain steroid hormones that can lead to severe depression. Like hypothyroidism, treatment of the underlying physical illness can be very effective in helping to treat the depression too.

Infections

• Certain viral infections, for example glandular fever (infectious mononucleosis) and influenza, are prone to trigger depression in vulnerable individuals.

Prescribed drugs

• Certain types of medication are associated with increased rates of depression, for example calcium channel blockers (eg nifedipine, nimodipine, verapamil) beta-blockers (eg propranolol, atenolol, metoprolol), corticosteroids (eg dexamethasone, hydrocortisone) and Levodopa (eg madopar, sinemet). If depressive symptoms develop after taking a new drug, then advice should be sought from a doctor about whether to try an alternative.

How do you recognize depression in such physical illnesses?

It is important to be aware of the possibility of depression, especially when a person is suffering from one of illnesses mentioned. The difficulty is that some of the key symptoms in depression are very common in these conditions, e.g. disturbed sleep, poor appetite and tiredness.

This makes these symptoms less helpful for doctors when making the diagnosis of depression. Furthermore, sadness is common following diagnosis of an illness as the sufferer comes to terms with their condition, but a prolonged 'low' mood with frequent weeping is likely to indicate depression has developed.

Symptoms that may indicate depression in somebody who is physically ill include:

• persistent sadness that does not lift with happy experiences.
• lack of interest in activities and pastimes that are normally enjoyed.
• loss of interest in sex.
• a loss of interest in friends and socializing.
• feelings of guilt and self-blame.
• marked pessimism about the future.
• suicidal thoughts and talk of wishing one were dead.

What causes depression in people with physical illnesses?

Just as the cause or causes of depression in people with no physical illness are often not clear, so it is with those who also have a physical illness.

There is good evidence that some of the above illnesses directly affect the parts of the brain and the chemical systems that control our mood and behavior. For example, vascular diseases (those affecting the blood vessels) and Parkinson's disease damage important areas of the brain, making people vulnerable to depression and perhaps triggering the illness.

Endocrine conditions directly interact with, and upset, important chemical systems governing mood and other features of depressive illness.

However, the psychological and social impacts of the illness are also very important. Suddenly losing function in a limb after a stroke, or struggling to walk after a heart attack, can lead to a number of social consequences - being unable to return to work, having to give up certain hobbies, etc. Such losses may trigger a depressive illness.

At the same time, these losses affect the sufferer's self-esteem and their roles at home and work may be changed, too. These factors may all contribute to the development of depression.

What should you do if someone is depressed and physically ill?

• Try to encourage the person to talk about their feelings and difficulties, because support from friends and family is important and not to be underestimated.
• However, if depression is suspected then you should seek help, usually through the family doctor (GP).
• The treatment of depression in somebody who is physically ill may include talking therapies and/or antidepressants.
• Support groups for the specific physical illnesses can be sources of information and understanding.