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DEAR DOCTOR: My dad and brothers are hunters, so there's always deer meat in the freezer and it's often on the menu. But I'm hearing that it's now linked to a brain disease. Should we be worried?

DEAR READER: You're referring to chronic wasting disease, also known as CWD, which has now been found in deer herds in at least 23 states. It has also been identified in moose, elk and reindeer, and is a becoming a problem in Canada, Norway and South Korea as well.

Chronic wasting disease is a progressive disease that affects the functioning of the brain and spinal cord of the infected animals, and invariably leads to their death. Although it is highly contagious among animals -- the disease continues to spread in wild deer herds and fenced-in hunting ranches -- there are no known cases of transmission to humans at this time.

CWD is part of a family of disorders known as prion disease. If that sounds familiar, it's because prions play a leading role in mad cow disease. The disease created an uproar when it was identified in Great Britain, Europe and the United States in the late 1980s through the early 2000s. Mad cow caused several hundred deaths in humans, mostly in Great Britain, and resulted in 4.5 million cows being destroyed.

Although prions are normal proteins found in the brains and nervous systems of most animals, including mammals, reptiles and birds, the prions involved in the disease process behave abnormally. They start a chain reaction among the normal proteins in the brain, causing them to fold and bend and become deformed. This prevents the proteins from fulfilling their specific biological purposes, and ultimately results in the characteristic spongy appearance in the brain tissues of the infected animal. In CWD, prions cause numerous small holes to develop in the brains of infected deer, which affect the deer's behavior and lead to death.

Symptoms in infected deer include tremors, loss of coordination, weight loss and wasting, a lack of awareness of the surroundings, an uncharacteristic loss of fear of humans, and increased thirst, urination and salivation. The incubation period of CWD is quite long, averaging from 18 to 24 months. That means an animal can be infected with the disease but not show any ill effects. CWD is transmitted among herds of deer through normal contact, like touching noses, licking, mating and giving birth. In addition, soil contaminated by the urine, feces or carcass of an affected animal remains a vector of infection for more than a decade.

CWD was first identified in the late 1960s, but as we mentioned earlier, there are no known instances of transmission to humans. However, because mad cow made the leap to humans, scientists are now investigating whether the same thing can happen with CWD. Wildlife officials in Colorado and other heavily affected states are urging hunters to bring their deer in for testing before consumption. This involves an analysis of tissues from the brain and lymph nodes. The agency that issued your hunting permit will have complete information.

DEAR DOCTOR: Just how addictive are antidepressants? My doctor thinks I should take one, but I know a lot of people who have had trouble stopping them. Do the drugs even work?

DEAR READER: Your questions land us in the midst of an important and ongoing discussion that has been taking place for some time now. Depression is a serious and sometimes life-threatening disorder that affects people of all ages, races and nationalities. According to the World Health Organization, it was the third-leading cause of disability throughout the world in 2004 and tops the list of disabilities in the developed world. A variety of medications to treat depression have been developed over the decades but have been accompanied by persistent questions about efficacy and long-term viability.

A specific group of symptoms, when experienced over time, mark a diagnosis of depression. These include low mood, low energy, feelings of worthlessness and an inability to experience pleasure, which is known as anhedonia. Additional symptoms can include altered sleep patterns, diminished appetite, an inability to concentrate and thoughts of self-harm. Diagnosis of depression, which can range from mild to moderate to severe, depends on accurate self-reporting of symptoms and of their duration.

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When it comes to medications, things get complicated. That's because the causes of depression are poorly understood. Research suggests the condition may arise from certain chemical imbalances in the brain, chronic stress and anxiety, response to life events, temperament and a genetic predisposition. Antidepressants tackle the various chemical pathways that are believed to play a role in the disorder. However, depression medications don't work for everyone. As many as two-thirds of patients don't respond to the first drug they try. But by working with their doctors to fine-tune their treatment regimens -- there are a number of classes of antidepressants, each with its own therapeutic pathway -- many patients living with depression do find relief.

When it comes to stopping pharmaceutical treatment, there's sobering news. Although antidepressants were originally developed for short-term use, six to nine months in most cases, the nature of depression and the scarcity of alternative treatment options meant patients have stayed on the drugs for years at a time.

According to a recent report in The New York Times, which analyzed federal data, more than 15 million people in the U.S. have been taking antidepressants for more than five years. When you look at the two-year mark for antidepressant use, that number jumps to 25 million. It's this long-term use that has been most often associated with adverse effects among patients who stop the drugs. Symptoms of withdrawal may include headache, fatigue, nausea, insomnia, unwanted feelings and unusual physical sensations. Tapering rather than quitting an antidepressant is important, and it should always be done in partnership with the prescribing physician.

While all of this may sound dire, it's important to note that antidepressants, when used properly and as part of a comprehensive treatment program, can be helpful. If you do decide to move forward with a prescription, talk all of this over with your doctor. Make a plan regarding duration, and never make any changes to your drug regimen without medical supervision.

Eve Glazier, M.D., MBA, is an internist and assistant professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and primary care physician at UCLA Health.

Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.

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