The Link Between Disease and Depression
When it comes to avoiding the frailty and disability of ageing, nothing beats preventing or treating depression.
While we’ve known for years that depression significantly increases your risk of death from heart disease, a major Norwegian study has found it also increases the risk of death from stroke, pneumonia, influenza, Parkinson’s disease and multiple sclerosis. One American study found that people with symptoms of depression were 42 per cent more likely to develop diabetes – the worse the depression, the higher the risk of diabetes. And a Dutch study showed that a history of depression raised the risk of Alzheimer’s disease by 2.5 times.
Depression is far more than just a low mood. Feelings of sadness and a lack of enjoyment of normal activities occur for most of the day, almost every day, and persist for weeks without relief. Typically they are most intense at the start of the day. People affected lose motivation, may find it difficult to concentrate and may feel exhausted, irritable, guilty, hopeless or worthless. General aches and pains may develop along with headaches, palpitations and chest pain, and sleep patterns and appetite are disturbed.
Internal and External
This is a complicated condition with many interacting causes. Sometimes depression is set off by external events, such as bereavement, debt, major surgery or a diagnosis of serious illness, including cancer or a heart attack. And sometimes it just happens – so-called endogenous depression. People with a family history of depression seem to be more vulnerable, as do those who abuse alcohol or drugs. Even some prescribed medications may precipitate depression. People with sleep disorders, women with young children and unemployed people are all more likely to become depressed, as are people in unhappy marriages, whereas those with supportive relationships seem to be protected. Some diseases, such as an underactive thyroid gland, are directly linked with depression. And researchers from the Institute for the Health of the Elderly at the University of Newcastle upon Tyne have shown that depression in later life may be associated with narrowing and hardening of the arteries supplying the brain.
The link between depression, disease and death? Recently an outpouring of research has highlighted links with chronic inflammation – the state of heightened immune system activity that doctors now believe is the underlying cause of so many diseases. People who are depressed have overactive immune systems that produce inflammation-promoting chemicals such as cytokines, which are known to influence many conditions that become more common with age. And people with inflammatory diseases are more likely to become depressed. Those with rheumatoid arthritis, for example, are two or three times as likely to become depressed as the rest of the general population – and when they are depressed their arthritis tends to get worse. This suggests that there is ‘cross-talk’ between the brain and the immune system.
Stress increases the production of cytokines, which may explain why stressful events can precipitate depression. Both stress and depression increase the risk of infections, which in turn promotes a further output of cytokines. The same vicious circle occurs with sleep disorders. There is also some evidence that stress and depression may permanently alter immune responsiveness, so that cytokine production and an enhanced inflammatory response are more likely even with minor stress or trivial infections.
All of which may explain why sometimes depression is prolonged, hard to treat and recurrent, and why it is linked with many chronic diseases associated with ageing. The good news is that taking steps to reduce stress, depression or inflammation may all enhance health. According to psychiatrists at the University of Glasgow, antidepressant drugs have potential anti-inflammatory effects, and treatments that reduce inflammation may have antidepressant effects. By getting your depression under control, you can minimise its impact on your overall life expectancy. So get professional help if you need it, and meanwhile try these tactics to prevent depression, or reduce its effects if it does.