Excellent question. Unfortunately, there's no simple answer for it. There are many kinds of depressive disorders, some more serious than others. It seems that depression has a wide variety of ways to enter your life:

• Some kinds of depression seem to run in families, so you may have a genetic predisposition to depression.

• Trauma and stressful life events can cause depression. The trauma doesn't have to have involved you personally to affect you. Stressful life events that can lead to depression include divorce, financial setbacks, chronic illness, loss of a job, and so forth.

• Hormones can cause depression. This means either a rise in hormone levels or a drop in them. Testosterone in men and progesterone and estrogen in women may be the culprits.

• Some medications can trigger depression or cause depressive symptoms. This includes prescription medications, as well as recreational drugs and alcohol. Also, drug interactions may have dangerous side effects, including depression.

• Certain other medical conditions can cause depression. Among them are heart disease, cancer, and HIV/AIDS.

• The weather can cause depression. The dark days of winter may lead to seasonal affective disorder (SAD), also known as The Alaska Effect.

Discovering what kind of depression you are dealing with may lead to understanding what caused it. Following the clues may lead you to the proper treatment.

Twins or triplets tend to run in certain families — it's a genetic trait. So is left-handedness and red-headedness. So, also, are certain forms of depression, including bipolar disorder. If you are beginning to wonder if you might be suffering from depression, it just makes good sense to take a look at your family tree and find out everything you can about the medical conditions that tend to appear more frequently than might be expected.

Did your father experience severe mood swings — so much so that you never knew quite what to expect from him when you were growing up? Was your mother constantly sad — to the point that you can't ever remember her being really happy? These are the kinds of things to look for as you take a trip down memory lane. Ask your aunts, uncles, cousins, or grandparents what they remember about other family members. Their responses may not come in medical terms, but they'll help you establish a connection to your past that will help guide your future.