You've probably seen the ad "Depression Hurts" - and know that stress can get anyone down. But being down for weeks or months on end goes beyond a simple funk.

Now, science may have a new tool to help those who either don't respond to traditional therapies, or simply have lost the will to help themselves.

Deep Brain Stimulation, says the Mayo Clinic (www.mayoclinic.com), can alter mood by using electrical impulses targeted to specific regions in the brain. Clinical trials are underway to better understand how the treatment works, and its potential side effects.

In this country, major depressive disorders have been linked to many of the more than 30,000 suicides recorded in 2002, according to the National Institutes of Mental Health (www.nih.nimh.gov). Nearly 15-million Americans suffer from such disorders, says the NIMH.

Of those, most will respond to standard treatments: anti-depressant drugs in combination with talk therapy, or, in severe cases, electroconvulsive therapy that "shocks" brain neurons into firing in a more normal fashion.

But for those who don't, Deep Brain Stimulation may bring relief from depression's symptoms:

• Loss of interest or pleasure in hobbies and activities you once enjoyed
• Decreased energy and fatigue
• Difficulty concentrating, remembering or making decisions
• Insomnia, early-morning awakening or oversleeping
• Appetite and/or weight loss or overeating and weight gain
• Thoughts of death or suicide; suicide attempts
• Restlessness, irritability
• Persistent physical symptoms such as headaches,
• Digestive problems and chronic pain
• A persistent sad, anxious or "empty" mood
• Feelings of hopelessness, pessimism, guilt, worthlessness or helplessness (Source: NIMH)

The Mayo Clinic says Deep Brain Stimulation requires two surgeries. The brain surgery is performed through two holes drilled in the skull. This is done while the patient is alert and can communicate with the surgeon, which helps ensure that the correct parts of the brain are being stimulated. Local anesthetic numbs the area where the holes are drilled.

On each side of the brain, electrodes are implanted. Then, in the second surgery, a neurostimulator device is implanted in the chest - not unlike how some heart patients are implanted with a pacemaker to regulate the beating of their hearts.

In Deep Brain Stimulation, the electrical impulses are controlled from the outside and patterned to each individual patient. The device regulates brain activity (altering the firing of the brain's neurotransmitters) 24 hours a day.

While not FDA-approved for depression, Deep Brain Stimulation is used for Parkinson's patients to control tremors. DBS is only available through a clinical trial and is considered risky and experimental. The Mayo Clinic says side effects may include:

• Bleeding in the brain
• Infection
• Delirium
• Unwanted mood changes
• Movement disorders
• Lightheadedness
• Insomnia

In Parkinson's patients, the procedure has also sometimes resulted in panic attack, speech problems, movement issues and even suicide. At present, follow-up studies have involved few patients, and long-term benefits/risks (if any) are not yet known.

However, according to the National Institutes of Health (www.nih.gov), at Emory University's School of Medicine, Dr. Helen Mayberg has used Deep Brain Stimulation to improve depression in four of six patients implanted with the thin wires through which a small electrical current stimulates areas of the brain researchers believe don't function properly in those who suffer from severe depression.

Mayberg's research group and others are also studying a non-surgical approach called Transcranial Magnetic Stimulation (TMS), in which a small electromagnet on the scalp delivers a current to the brain. Apparently well focused, the technique doesn't appear to have side effects, has been promising in small studies, and is now funded by the NIMH for a large clinical trial.

If you know someone you believe is suffering from clinical depression, the NIMH suggests that you:

• Tell the person that you are concerned about him or her.
• Talk to the person about seeing a doctor.
• Take the person to a doctor.
• "Be there" for the person after he or she starts treatment.
• Take any comments about suicide or wishing to die seriously.

The toll-free 24-hour suicide prevention hotline is (800) 273-TALK (8255). For information on Deep Brain Stimulation and Transcranial Magnetic Stimulation clinical trials, visit www.clinicaltrials.gov.