It's common to think of depressed people as being sullen or morose, but anger can also pop up in the early stages of depression.

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Everyone feels "down" at times, but for some, the feeling settles in like a heavy fog that doesn't lift for weeks, or even years. When a sense of sadness turns to long-term despair, it's very likely a condition called major depression.

While researchers continue seeking answers for the chemical causes and evolutionary origins of major depression, what's not up for debate is the fact that it's all too often fatal. As many as 12 percent of people with major depression end up committing suicide [source: Friedman].

Anyone -- male or female, young or old -- can experience major depression. Depression seems to have a hereditary link, but occurs without it as well [source: Zieve]. While major setbacks or trying life events often precede a first occurrence, subsequent episodes of major depression can occur without any apparent prompt at all [source: Friedman].

A person in the throes of major depression will outwardly seem to be in a state of self-isolation, lethargic, irritable and may have unusual sleeping or eating habits (in either case, too much or too little would qualify as "unusual"). But while we often think of people with depression as being sullen or morose, both the depressed person and those he or she comes into contact with may notice one other emotion in the early stages of depression: anger.

The depressed person may lash out at loved ones, or even strangers, and seem uncharacteristically consumed with rage. Anything may set off the outbursts, and even when it's not being expressed, anger might be occupying his or her thoughts [source: MacManamy].

So why would depression cause anger? And can it ever be the other way around? How can you effectively treat both problems? We'll discuss that on the next page.