"Depressive disorder" is a generalized term. As the National Institute of Mental Health (NIMH) explains, there are a variety of depressive disorders, the most common being major depressive disorder and dysthymic disorder. While these disorders vary in the criteria needed for diagnosis, they do have one thing in common--causes and risk factors. In fact the causes and risk factors are similar for all depressive disorders, regardless of the type or how they are categorized.
Genetics
The National Alliance on Mental Illness (NAMI), NIHM and the Mayo Clinic all agree that depression, no matter what the type, has a tendency to run in families. When depression runs in families, biological members have an increased risk of developing the condition.
The NIMH states that this risk is due to the influence of multiple genes acting together with other risk factors such as environmental influences. It should be noted that not all persons with a genetic link will develop depression according to NAMI.
Physical Differences In the Brain
Magnetic resonance imaging (MRI), a brain-imaging test, shows that the brains of those with depression look different than those who do not suffer from this illness according to the NIMH. This test shows that the neurotransmitters (chemical messengers) responsible for mood regulation, thinking and sleeping appear to be out of balance. These chemicals include serotonin, dopamine and norepinephrine.
NAMI states that these three chemicals transmit electrical signals to the brain. When they are out of balance, the cells do not receive the correct signals, resulting in depression. Antidepressants either change the sensitivity of these chemicals' receptors, or increase the number of neurotransmitters available, therefore restoring balance and reducing the symptoms of depression.
Hormones
The NIMH states that depression is more common among women than it is men, due to hormonal factors. Hormones directly affect the brain chemistry responsible for controlling mood and emotions. An example of this is postpartum depression, a condition some women suffer from after giving birth. This is due both to the physical and hormonal changes women experience during this time. It is suggested, however, that some women who suffer from postpartum depression may have experienced prior episodes of depression.
Other examples of depression in women due to hormonal changes in the body include a severe form of premenstrual syndrome (PMS), known as premenstrual dysphoric disorder (PMDD). This condition takes place near the time of ovualtion and lasts until menstruation begins. It is a result of changes in hormones, which increase some women's chances of suffering from depression.
Evvironmental Factors
Environmental factors include events such as the break up of a relationship, financial difficulties or losing a job. Some people are able to cope better with these situations, while others are not.
In some cases environmental factors can include traumatic events from a person's childhood, such as the loss of a parent or a loved one, physical or sexual abuse or lack of support from a parent, all of which leads to low self-esteem. Any or all of these factors can cause permanent changes in the brain explains the Mayo Clinic, making one more susceptible to depression.
