What causes depression?
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, that 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 someone 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 employed. In this
model, consideration is given to biological, 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
biological 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, psychotic, or
substance abuse disorders, 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.
