Dear Doctor: Given a choice, I'll always choose white wine over red. But a recent study linking white wine to increased melanoma risk made me reconsider. Am I overreacting?

Dear Reader: This is a difficult question without a simple answer -- so let's start with some basics. Alcohol metabolizes into the chemical acetaldehyde, which can cause DNA mutations that lead to cancer. To date, alcohol has been associated with an increased risk of cancers of the breast, colon, liver and pancreas.

A 2014 analysis of many different studies published in the British Journal of Dermatology found an 18 percent increase in melanoma among people who drank more than one alcoholic beverage per day, regardless of the type. This analysis was based on retrospective studies, which are studies assessing people's past habits after a diagnosis has been made.

Prospective studies follow patients prior to the diagnosis of disease. The research to which you're referring was that type of study, and was published in the journal Cancer Epidemiology, Biomarkers and Prevention. For their analysis, researchers looked at data on disease outcomes from three studies of health care professionals and tied those outcomes to potential risk factors. The three studies combined followed a total of more than 210,000 people over a period of more than 18 years. In the studies, participants were asked to state their level of alcohol consumption and to also state what type of alcohol they consumed.

Researchers found that overall, 1,374 people (less than 1 percent) were ultimately diagnosed with melanoma. Those who drank alcohol, however, had a 14 percent increase in the rate of melanoma, and that number increased to 21 percent in those who had one or more drink per day. Note that people who drank more alcohol also reported higher rates of smoking, caffeine intake and previous severe sunburns. The authors adjusted for this, so the data still appears relevant.

So yes, alcohol appears to slightly increase the risk of melanoma.

As for wine, some types -- especially white wines -- have more acetaldehyde and thus could have a greater ability to increase cancer risk than other types of alcohol. But when the authors looked at the type of alcohol consumed, the results between the three studies varied tremendously.

Consider that in one study, of male health care professionals, the researchers found a greater rate of melanoma among men who drank white wine one to three times per month compared to those who drank white wine two to four times per week. Even taking that finding into account, the authors overall found a 13 percent increased rate of melanoma with each drink of white wine per day. They did not find such a high rate with other types of drinks.

The current study has two potential problems, however. One is that the authors did not differentiate whether drinkers of white wine also drank other types of alcohol. Also, and this may be the biggest issue, because white wine is often drunk cold, people who drink white wine may be more likely to live in sunnier places and thus have more sun exposure.

The authors did look at this second point and found that the majority of melanomas that appear to be related to alcohol consumption occurred on the less-sun exposed areas of the chest, abdomen and back. If the melanomas were linked to sun exposure, instead of wine consumption, the cancers would have been more likely on exposed areas of skin, such as the arms and face.

In summary, drinking alcohol does appear to slightly increase the risk of melanoma. While this study on the impact of white wine does not appear convincing, white wine drinkers should consider the fact that acetaldehyde is carcinogenic and white wine has more acetaldehyde.

Myself, I will reflect on this the next time I have a glass of pinot grigio on a hot summer day.

(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.)

Dear Doctor: It's been two weeks since our son was born, and my wife seems to be having a hard time. She cries easily and has a lot of anxiety. Is this just baby blues, like my mother says, or is it postpartum depression?

Dear Reader: Congratulations on welcoming a new baby! Your lives have undergone an enormous change, and that's at the heart of your wife's difficulties. Both in the short-term disruption of the so-called "baby blues" and the more serious struggle of postpartum depression, the physical, emotional and hormonal changes a woman goes through after she gives birth can often pose challenges.

First, let us reassure you that at two weeks postpartum, it's perfectly natural for a new mother to feel overwhelmed. Up to 80 percent of new mothers report symptoms of mood swings, anxiety, mild depression, weepiness and negative thoughts or feelings in the first few weeks after the baby arrives.

Your wife's body is not only recovering from the physical and emotional rigors of the birth process, but it is also now returning to its pre-pregnancy state. That means she is experiencing a sudden drop in hormone levels -- estrogen and progesterone in particular -- which have been at record levels during her pregnancy. Add in sleep deprivation and the seismic changes to her daily routine as she learns new tasks and takes responsibility for a new life, and it's little surprise that she feels overwhelmed.

When these symptoms don't go away after several weeks, or if they become more severe, then postpartum depression becomes a possibility. When this is the case, seeing a primary care physician is vital.

Symptoms of postpartum depression mirror those of major depression. These include a sad or empty feeling that won't go away, feelings of hopelessness or worthlessness, pervasive pessimism, a change in sleeping or eating habits, withdrawal from loved ones, and often a lack of connection to or interest in the new baby. Between 11 and 18 percent of new mothers experience postpartum depression. Fortunately, most women who seek treatment for postpartum depression will recover.

Meanwhile, there's a lot that you can do to help your wife right now. Simply listening is important. Get her to talk about how she's feeling and what she's going through so she knows that you care and understand. It's quite likely you both have some of the same feelings, and sharing them can help build up your bond.

Help around the house without being asked. Make a meal, do housework, arrange for her to have some time to herself. Something as simple as getting outside can make a big difference. A daily walk will be good for both of you. Even a drive through the neighborhood just to look around can bring welcome distraction.

The baby blues are an isolating experience that comes at a time of life when women are told they should be happiest. By stepping up to lend a hand, you're not only helping your wife recover, you're also setting the foundation to a parenting partnership.

(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.)

(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.)

Dear Doctor: I try not to use opioids for my chronic back pain, but I'm finding myself turning to them more often. Could marijuana help?

Dear Reader: Pain is one of most difficult aspects of medicine to understand. No one can actually feel the pain of another person, but we can see the suffering that it causes. As doctors, we try to alleviate pain in a number of ways.

Opiates -- starting with opium, which is derived from the poppy plant -- have been used for pain relief for more than 3,000 years. The opiates morphine and codeine, also from the poppy plant, were isolated and made available in the early 1800s. Since that time, multiple synthetic opiates such as hydrocodone and oxycodone have been widely used for pain. These drugs attach to opiate receptors in both the brain and spinal cord.

One problem with opiates is that they relieve pain in the short term, but will not control it in the long term. Thus to relieve chronic pain, a person has to perpetually use the medication -- creating one of the addictive aspects of the drugs. The other problem with opiates is that people become tolerant of the medications, meaning that with consistent use, a person needs more medication to relieve the same amount of pain.

For these reasons, opium and its progeny have been abused worldwide. The United States is facing an epidemic of opiate abuse, with prescription opiate medication leading to a rapid increase in lethal drug overdoses. In 2014, more than 18,000 people died from overdosing on prescription opiates, according to the federal Centers for Disease Control and Prevention.

Marijuana has been used also for more than 3,000 years. It works through the endocannabinoid system of the body, which has receptors in the brain and spinal cord as well as the immune system. The receptors in the brain and spinal cord can decrease muscle spasms and pain, while those receptors in the immune system can decrease inflammation and pain.

A 2015 study published in the Journal of the American Medical Association (JAMA) looked at 14 different clinical trials of marijuana use by multiple sclerosis patients and found relief from chronic pain, nerve pain, and pain and muscle spasm. Another study published in 2015 in JAMA looked at 28 different studies with 2,454 patients and found a 30 percent reduction of pain with cannabis-related products compared with placebo.

Opiates can relieve pain in the short term, such as after surgery or an acute injury. But due to their addictive potential and lack of long-term benefit, opiates are not a good choice for long-term pain relief.

Marijuana is not without its own potential risks and side effects. These include short-term memory loss, poor motor coordination, paranoid thoughts and, for some, psychosis. Long-term use can also create the potential for addiction, but not to the degree of opiate medications. Also, overdosing on marijuana doesn't lead to death, as it can with opiates.

My suggestion in regard to chronic back pain is to try other methods of pain control over opioids. These include physical therapy, yoga and stretching. If these don't work, marijuana is an option, but beware of its side effects -- and try to minimize its use.