Anthony’s comment:
Although depression is not 100% heritable, I believe it often runs in families even if one is not aware of it being present in other family members. In the early 1970s, due to severe anxiety over my identity, I went to see a psychiatrist and received treatment with medication. I needed something that allowed me to function. I was the only one in my extended family, however, who ever sought professional help to deal with anxiety and depression. As a result I was labeled with everything under the sun. But, although no one else has actually been diagnosed with depression in my family, it is my impression that there are in fact family members who deal with depression and anxiety, but due to unawareness, stigma, etc. have not been formally diagnosed or treated.
The causes of depression are not easily defined. When speaking of cause, it is typical to think in terms of infections of the lungs causing pneumonia or of cigarette smoking causing lung cancer. In actuality, most medical conditions cannot be so easily defined as having clearly linked causes. In fact, it took many years of statistical analysis before scientists could demonstrate a clear causal link between cigarette smoking and lung cancer. Even today, people argue, “My grandmother smoked her entire life and died at the ripe old age of 90 from natural causes. How can cigarettes possibly cause cancer?”
The reality is that cigarette smoking is only one portion, albeit a big one, of the causal puzzle, which when pieced together leads to lung cancer. This is true of most diseases today. Instead, when physicians talk about cause, they are really talking about risk factors that influence the odds of developing a particular illness. Depression, a complex illness, is more like an illness with multiple causes that influence the odds of someone developing it.
Depression runs in families but is not 100% heritable. Depression may occur in some-one with no family history for the illness. When considering the causes of depression, the odds are impacted by a variety of sources inside and outside of a person. This variety constitutes what is called the biopsychosocial model that is typically used. In this model consideration is given to biologic, psychological, and social factors that may contribute to the onset of depression. This model influences most diseases of lifestyle. Look at, for instance, heart disease. Applying the biopsychosocial model to heart disease demonstrates biologic risk factors of family history, the presence of high blood pressure and high cholesterol, and atherosclerosis; psychological risk factors of type A personality and/or an inability to handle stressful events; and social risk factors of smoking, diet, and activity level.
Biologically, depression is associated with changes in various neurotransmitter levels and activity, commonly referred to as a chemical imbalance in the brain. Additionally, depression frequently runs in families, suggesting a genetic, or heritable, aspect to the illness. Medical conditions and sometimes the medications used to treat those conditions can also cause depressive symptoms. Psychologically, certain personality types are more prone to developing depression.
People who have low self-esteem and a pessimistic outlook are at higher risk for depression. Other psychological disorders, such as anxiety, psychosis, or substance abuse dis-orders, increase the odds of developing depression. Socially, depression is linked to stressful life events, usually entailing loss, such as of a spouse, child, job, or financial security. Depression, however, can also be linked to events generally considered to be uplifting rather than stressful, although from the body’s reaction they are stressful. These events can include marriage, the birth of a child, a job change or promotion, or a move to a new neighborhood or home.