Depression can affect anyone at almost any age. And the reasons why some people grow depressed isn't always known. But, researchers suspect there are many causes of depression and it isn't always preventable.
It's estimated that 10 to 15 percent of the general population will experience clinical depression in their lifetime. And the World Health Organization estimates 17 percent of men and 9 percent of women experience depressive disorders in any given year.
Genetics and Biology
Twin, adoption, and family studies have linked depression to genetics. But, researchers are not yet certain about all the genetic risk factors for depression.
But at this time, most researchers suspect that having parents or siblings with depression may be a risk factor.
Brain Chemistry Imbalance
Depression is believed to be caused by an imbalance in the neurotransmitters which are involved in mood regulation.
Neurotransmitters are chemical substances which help different areas of the brain communicate with each other. When certain neurotransmitters are in short supply, this may lead to the symptoms we recognize as clinical depression.
Female Sex Hormones
It has been widely documented that women suffer from major depression about twice as often as men. Because of the incidence of depressive disorders peaks during women's reproductive years, it is believed that hormonal risk factors may be to blame.
Women are especially prone to depressive disorders during times when their hormones are in flux, such as around the time of their menstrual period, childbirth, and perimenopause. In addition, a woman's depression risk declines after she goes through menopause.
Circadian Rhythm Disturbance
One type of depression, called seasonal affective disorder (officially known as major depressive disorder with seasonal pattern) is believed to be caused by a disturbance in the normal circadian rhythm of the body.
Light entering the eye influences this rhythm, and, during the shorter days of winter, when people may spend limited time outdoors, this rhythm may become disrupted.
People who reside in colder climates where there are short, dark days may be at the highest risk.
Poor Nutrition
A poor diet can contribute to depression in several ways. A variety of vitamin and mineral deficiencies are known to cause symptoms of depression.
Some studies have found that diets either low in omega-3 fatty acids or with an imbalanced ratio of omega-6 to omega-3 are associated with increased rates of depression. In addition, diets high in sugar have been associated with depression.
Physical Health Problems
The mind and the body are clearly linked. If you are experiencing a physical health problem you may discover changes in your mental health as well.
Illness is related to depression in two ways. The stress of having a chronic illness may trigger an episode of major depression.
In addition, certain illnesses, such as thyroid disorders, Addison's disease, and liver disease, can cause depression symptoms.
Drugs
Drugs and alcohol can contribute to depressive disorders. But, even some prescription drugs have been linked to depression.
Some drugs that have been found to be associated with depression include anticonvulsants, statins, stimulants, benzodiazepines, corticosteroids, and beta-blockers.
It's important to review any medications that you've been prescribed and to speak with your physician if you are feeling depressed.
Stressful Life Events
Stressful life events, which overwhelm a person's ability to cope, may be a cause of depression.
Researchers suspect high levels of the hormone cortisol, which are secreted during periods of stress, may affect the neurotransmitter serotonin and contribute to depression.
Grief and Loss
Following the loss of a loved one, grieving individuals experience many of the same symptoms of depression. Trouble sleeping, poor appetite, and a loss of pleasure or interest in activities are a normal response to loss.
The symptoms of grief are expected to subside over time. But when symptoms get worse, grief may turn into depression.
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