Lately you've been feeling down—crying for little to no reason, with an overwhelming sense of sadness that you just can't shake. Is this "normal" sadness—"the blues" that everyone gets from time to time—or have you become clinically depressed? Experts say normal, everyday sadness can be distinguished from depression in several ways. Has your sadness lasted longer than two weeks? Sadness as a normal human reaction to life events is typically short-lived. You may have several days of darkness—and then it dissipates. Depression, on the other hand, is unrelenting and long-lasting. You don't shake the blue feelings after two weeks; they go on and on. Is there a cause for your sadness? Are you feeling sad for a reason—a loss or disappointment, such as getting fired from a job or going through a divorce, for example? This is to be expected as a typical reaction for a healthy person. However, if you are experiencing deep sadness for no apparent reason, this can be a sign of depression. (This doesn't mean that you can't get depressed after losses or other sad life events; this can happen, too.) Has your sadness interfered with your daily life? You can still work when feeling down in the dumps. Something funny can bring a smile and your mood can be broken, at least for a few minutes. Depression, on the other hand, is unremitting. It affects your ability to work, your relationships, your sleep, your eating habits—pretty much every aspect of your daily life. The sadness you feel not only is constant but also excessive. Do you have other signs of depression? Besides sadness, depression comes with a host of other symptoms. Not every person with depression will have all of them, but if you have five or more of the following symptoms for more than two weeks, you are likely to have depression. (Note: At least one of the five symptoms must be depressed mood or loss of interest): Depressed mood, characterized by sadness, emptiness, tearfulness or constant irritability, which occurs most of the day for nearly every day Significantly reduced interest or pleasure in activities most of the day nearly every day Significant weight loss (without dieting), weight gain, or changes in appetite Sleep disturbances: insomnia or increased desire to sleep Restlessness or irritability Fatigue or loss of energy Feelings of worthlessness, helplessness, or hopelessness Inappropriate guilt Trouble concentrating, thinking, or making decisions Recurring thoughts of death or suicide; or, a suicide attempt If you have depression, you are not alone. Depression affects about 6.7% of the U.S. population older than 18 in any given year—approximately 15.7 million adults. There are several types of depression: Major depression includes the symptoms listed above. It can be disabling. People may have an episode of major depression only once, or it may recur frequently. The depressive episode may start as a reaction to a sad experience or it may begin spontaneously. Persistent depressive disorder is a depressed mood that lasts at least two years. Someone with this disorder may have major depressive episodes alternating with times where the symptoms are less severe, but they continue to persist. Seasonal affective disorder (SAD) is depression that occurs during months where there is less sunlight, such as winter and fall, and eases during spring and summer. Postpartum depression is depression that affects 10 to 15% of women after they have given birth. Psychotic depression occurs when a person with depression also experiences psychosis (characterized by delusions, a break with reality, or hallucinations). Bipolar disorder is marked by both depression and mania (with moods cycling between extreme lows and highs). If you think you may have depression, it's important to seek medical attention. Unchecked, depression can up-end lives, cause people to lose jobs and relationships—and ultimately could lead to suicide. Depression is the cause of more than two-thirds of the 30,000 suicides committed annually in the United States. Most people with even the most severe forms of depression get better with treatment, which can include medication, psychotherapy, attending support groups, and other methods. You can search right here on Healthgrades for a psychiatrist or counselor near you.