Dear Doctor: I just read about a study that says exercise cancels out alcohol's higher risk of death from cancer. Is it possible that I can walk off the cancer risk of the cocktail I have each night after dinner? (For the record, my husband is sure that you're going to say no.)

Dear Reader: While we commend your creative thinking, your husband has guessed right. In our opinion, you can't depend on added exercise to cancel out the increased risk of cancer that can be caused by alcohol consumption. It's not that we think the study itself is wrong. It's the way the results have been interpreted in some news stories -- as cause and effect -- that is, at best, misleading.

Let's start from the beginning.

Researchers in England looked at a decade of medical data collected from 36,370 women and men, all 40 or older. They sorted the study subjects by how much alcohol they consumed and by how much they exercised.

Not surprisingly, they found a statistical link between "hazardous drinking" and an increased risk of death from all causes, including cancer. In this study, hazardous drinking was defined as 8 to 20 servings of alcohol per week for women, and 21 to 49 servings of alcohol for men.

Then the researchers included exercise as a variable in their calculations. They found that among people who spent at least 150 minutes per week doing moderate aerobic activity, like a brisk walk, the mortality rate due to cancer dropped. This proved to be true even among the heavier drinkers, as long as they exercised.

On its face this seems to suggest, as many news reports went on to state, that exercise can cancel out the elevated risk of cancer due to drinking. But -- and this is crucial -- this is what's known as an observational study. That means the study is based solely on data collected from the same subjects over a period of time.

While studies like these are useful for pointing out the existence of certain patterns based on the information at hand, they can't be used to prove cause and effect. The level of exercise among the drinkers is just one among countless variables that can play a role in whether someone goes on to get cancer. These variables include genetics, family history, diet, environmental causes, and levels of stress and anxiety, to name just a few. Even how forthcoming and reliable the study's subjects were in self-reporting their drinking and exercise habits would have an impact on the outcome.

That said, what this study does do is add to the significant body of existing evidence that exercise plays a role in good health. Exercising may not automatically equal risk-free drinking, but people who exercise regularly do get some pretty great benefits. It can help maintain weight, aid in weight loss, bolster cardiovascular health and play a role in maintaining healthful blood lipid levels. It can also help with sleep and boost mood.

Get your husband on board and maybe instead of a nightly cocktail, the two of you can head outside after dinner for a companionable (and brisk) walk.

(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.)

Dear Doctor: My husband has seemed really down since the birth of our son six months ago. We're both being run ragged, and very proud of our son, but my husband seems less happy than I had hoped he would be. Could he be suffering from postpartum depression? If so, how? I'm the one with the hormonal onslaught!

Dear Reader: "Running ragged" is a good description of parents in the first year of a child's life. Many have described it as going into a tunnel. Metaphorically, it can get mighty dark in there. Parents and their new child grope around to find some sense of normalcy, when every day brings a new change or a new obstacle. Adding to these challenges for women is the drop in the hormones estrogen, progesterone and oxytocin after pregnancy, which can trigger mood fluctuations and postpartum depression. Men don't have that same hormonal drop, but that doesn't mean they don't experience changes.

Studies in mammalian fathers, including humans, who take care of newborns have shown drops in their testosterone levels after birth and a rise in their levels of prolactin, a hormone typically linked to a female's ability to produce milk. Evolutionarily, it makes sense that men who are helping to take care of children should have a drop in testosterone. Testosterone is needed for procreation, which should be the last thing on a dad's mind when he's taking care of a child. In fact, studies in multiple societies have found that the more hours a father invests in childcare, the lower his testosterone level will be.

A recent study in the journal Hormones and Behavior attempted to evaluate levels of testosterone and postpartum male depression in 149 low-income males (30 percent had household incomes below the poverty line). Fathers and mothers were assessed for postpartum depression, parenting stress, relationship satisfaction and intimate partner aggression. These assessments were performed one to three months after birth, six to nine months after birth and 12 to 16 months after birth. Also, at nine months after birth, the fathers underwent salivary testosterone testing.

Lower testosterone in fathers at nine months after birth correlated with increased depressive symptoms at that time, but not when depression was tested again at 15 months. Men with depressive symptoms at nine months also reported increasing parenting stress six months later. Interestingly, though, lower testosterone in the father at nine months was associated with less postpartum depressive symptoms in the female partner at nine months and 15 months.

The men with higher testosterone levels had decreased depressive symptoms at one to three months after birth, but this did not hold true at the six-to-nine month and 12-to-16 month intervals. However, the female partners of the men with higher testosterone levels reported more depressive symptoms and more feelings of aggression from their partner at the six-to-nine and 12-to-16 month intervals. Also, men with higher testosterone levels had increased parenting stress at 15 months.

The findings are complex, but they show that hormone levels do indeed fluctuate in men, affecting their psyche, their outlook and their relationships. Specifically, higher and lower levels of testosterone are linked to psychological changes in both parents.

As you know, being a parent isn't easy. Aside from the hormonal changes, parents of both genders can face financial pressures, sleep deprivation and the realization that life has changed dramatically. Each person processes and adjusts differently. My advice: Keep communicating. Your son will benefit from it.

(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.)

Dear Doctor: I had shingles about 10 years ago, just after I turned 50, and it was just as difficult and painful as everyone says. Now I hear that it's possible I can get it again. Is this really true? Should I get the vaccine?

Dear Reader: Unfortunately, it's true that having had shingles once does not bestow immunity. While a second bout is rare -- it's estimated that as few as 1 percent of people who have had shingles get it again within the first three years -- the odds do increase over time. According to the Centers for Disease Control and Prevention, 7 percent of people who have had shingles will go on to have another bout within seven years.

For those who don't know, shingles is a nasty rash that can occur in people who have previously had chicken pox. It happens when the varicella zoster virus, which causes chicken pox, emerges from its dormant state and travels along nerve fibers to the skin. In addition to a blistering rash, shingles can be accompanied by nerve and muscle pain and extreme skin sensitivity. Although you can get shingles at any age, half of all cases occur in people 60 and older.

Someone with active shingles can't spread the rash, but because the liquid in the blisters contains the virus, they can spread chicken pox. That makes it vital to not have physical contact with anyone who has not had or has not been vaccinated for chicken pox while you have shingles. As though the pain, itching and burning of the rash weren't bad enough, people with shingles also run the risk of being left with ongoing nerve pain, a condition known as post-herpetic neuralgia.

While this all sounds quite grim, there is some encouraging news. A new shingles vaccine called Shingrix has been released. In clinical trials with over 38,000 people, it has shown to be 90 percent effective in preventing shingles in people between 50 and 80 years old, according to clinical data from the CDC. However, when the age groups between 50 and 80 are analyzed separately, efficacy varies.

The two-dose vaccine got a preliminary nod from the CDC in October. An advisory committee recommended that Shingrix should be administered in place of an older existing vaccine, called Zostavax. Given in a single dose, Zostavax isn't as effective as the newer vaccine. It offers a 51 percent reduction in shingles, and reduces nerve pain by about 65 percent.

The CDC's advisory committee is recommending that individuals 50 and older be vaccinated with Shingrix. The committee is also urging that anyone who has already been vaccinated with the older, single-dose vaccine now also receive the new one. The vote in favor of the new vaccine was not unanimous, however. In fact, it was nearly a split decision, with eight members voting for the new guidelines, and seven voting against. A final recommendation from the CDC regarding Shingrix could come as soon as next year.

In the meantime, we would suggest you discuss these developments with your doctor. If you are a candidate for either the new or old vaccines, they may help prevent a recurrence of a painful and challenging condition.

(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.)