Changes to the brain due to depression
In depression, chemical changes occur in some pathways of the brain. These changes may vary with different forms of depression. However, it is not known whether these chemical changes cause depression or are one of the consequences of it.
In classic unipolar depression, the chemical changes may include alterations in the number or the sensitivity of nerve cell receptors for certain neurotransmitters (chemical messengers). The receptors for serotonin or 5HT (5-hydroxytryptamine), noradrenaline and dopamine, in particular, may be affected.
Serotonin or 5HT is involved in the regulation of mood and in maintaining normal patterns of appetite, sleep and sexual activity. Therefore, any abnormality in the 5HT pathways may lead to disturbance of sleep, increased anxiety and irritability and loss of sexual desire. These are all classic symptoms of depression.
Noradrenaline helps regulate mood and energy, both of which plummet in depression. Changes in the level of noradrenaline may lead to the overwhelming fatigue, loss of enthusiasm and social withdrawal that are characteristic of depression.
Dopamine plays a role in gaining pleasure and changes in this chemical messenger may therefore lead to the feeling that it is impossible to derive enjoyment from activities that you normally like. Abnormalities in dopamine may be especially important in people with manic depression (bipolar disorder).
Changes in all three of these neurotransmitters, known as monoamines, may be involved in depression. Other chemical messengers may also be associated with depression. Some evidence shows that changes within the brain are associated with the levels of certain hormones in the bloodstream.
It is not yet possible to test for the levels of all these chemicals in the brain, but it may become so in the future. A test for serotonin levels already exists, but it is crude and unreliable at present.
The genetic component
Certain genes also have an effect on depression, but the genetic picture remains unclear. Molecular biologists have, for some years, been confident of isolating the exact part of the gene or genes responsible for the development of depression. This knowledge will greatly help the development of new and better treatments.
It is known that depression runs in families, but it is not necessarily hereditary. It is simply that the risk is increased if depression already exists in the family, especially in parents or siblings.
Generic Risk Factors of Depression
- If one identical twin develops severe depression, the other has a 50 percent chance of becoming depressed.
- Depression in one non-identical twin signifies a 25 percent chance in the other of becoming depressed.
- The risk to children both of whose parents both suffer with depression is over 50 percent.
- Someone with a parent with manic depression has a 20 times greater chance of developing depression than someone whose parent does not have it.
- Postnatal depression is more like in women who have a family medical history of depression.
- Depressed children have about four times the likelihood of developing depression in their adult lives.
Key Facts: Depression can be treated very effectively, even though its cause is not fully understood. If depression already exists in your family, you run a higher risk of developing it than someone who does not have a family history of depression. Depression is associated with changes in one or more chemicals in the brain but it is not known whether these changes are a cause or an effect of depression.