If you experience depressive symptoms and feel sad all the time, you're probably suffering from what doctors call a "unipolar" disorder. But some older people develop another type of depression called "bipolar" disorder or manic depression, in which their low moods alternate with episodes of mania or exaggerated elation. Although the disorder tends to show up earlier in life.

Here are the warning signs of mania. (Mania can also occur on its own, unaccompanied by periods of depressed mood.)

Unlike other types of depression, manic episodes tend to develop suddenly, within a period of days or weeks.

The person seems to be in an unusually cheerful or "high" mood all the time, although there may also be periods of suspicion or irritability that can lead to violent outbursts.

There's often extreme physical and mental restlessness the person seems to be rushing around constantly from place to place, project to project, thought to thought.

Speech is unusually loud and rapid, and it's difficult for someone else to stop or interrupt the flow of conversation.

The person spends much less time sleeping or resting.

There's often a lack of judgment, which can lead to involvement in high-risk activities such as gambling, shopping sprees, new business ventures or investments, and sexual promiscuity.

The person may show signs of grandiosity or inflated self-esteem, imagining himself to be someone famous. Sometimes this can progress to actual hallucinations or delusions.

Manic episodes can be extremely debilitating for the sufferer and upsetting for family members who must cope with their relative's frantic activity. In extreme cases the person must be hospitalized to protect him self and others. If you or someone you know seems to be suffering from manic depression or mania alone, it's important to get treatment right away.

Your doctor will want to rule out delirium and eliminate the presence of an underlying physical illness such as a thyroid disorder. She will also examine whether the behavior might be a side effect of certain medications for example, some tranquilizers, ulcer drugs, antidepressants, anti-Parkinson drugs and amphetamines can cause manic symptoms, as can alcohol and cocaine.

Treatment for manic depression involves medication in the form of lithium salts, which can stabilize moods in about half of all sufferers. Because lithium usually takes about two weeks to become effective, you may also be given a short course of antipsychotic medications such as haloperidol, or other drugs such as carbamazepine and valproic acid, which can stabilize your moods.

Since lithium can be toxic in excess, you will probably need to have regular blood tests. Common side effects include thirst, frequent urination, nausea, diarrhea and weight gain. Here's some advice to remember should you or someone you know be diagnosed with manic depression.

Most researchers now believe that manic depression is a hereditary disease involving an imbalance in brain chemistry. This means that the symptoms aren't under your control, and you shouldn't blame yourself for your behavior.

It's absolutely vital that you continue taking your lithium, since you can easily suffer a relapse. If side effects are a problem, let your doctor know.