Dear Doctor: Do marijuana users really have more sex? Why would that be? I ask out of simple curiosity, of course.

Dear Reader: I suspect you're referring to a recent, much-publicized study in the Journal of Sexual Medicine. Before I answer your question, however, let's consider: Why is sex so important? From a biological perspective, male-female sex is necessary for procreation and, without it, none of us would be here. But aside from the sperm-meets-egg function of intercourse, greater amounts of sex with one partner have indeed been linked to greater happiness.

A 2015 study in the journal Social Psychology and Personality Science analyzed data from three studies totaling more than 30,000 people. The study looked at sex frequency, relationship satisfaction and happiness. The authors found that, although sexual frequency led to greater relationship satisfaction and happiness, those factors plateaued when sex occurred four to six times per month -- meaning that having sex more than once a week did not alter relationship satisfaction or happiness compared to having intercourse once a week.

This brings us to the latest study in the Journal of Sexual Medicine. The authors analyzed data from a health questionnaire called the National Survey of Family Growth. Participants ages 15 to 44 were asked about their frequency of intercourse four weeks prior to the survey. The participants also were asked about their frequency of marijuana use; 28,176 women and 22,943 men participated in the study, with an average age of about 30.

Granted, the study's parameters were narrow, featuring only questions about male-female sex. Still, marijuana use did correlate with higher sexual frequency. In a four-week time period, men who had never used marijuana had sex an average of a little more than five times; men who used marijuana weekly had intercourse an average of six times; and men who used marijuana daily had sex an average of seven times. Among women, those who had never used marijuana had intercourse an average of six times, while those who used it weekly or daily had intercourse an average of seven times.

Keep in mind, however, that the link between marijuana and sex is a correlation -- it doesn't reflect causation. The true connection between the two may simply be risky behavior. That said, for many people, marijuana is a relaxant, helping them forget their anxieties. It also decreases inhibition, and many users report that sexual experiences are more pleasurable with the drug. So it's simple to deduce how marijuana could increase sexual frequency.

Regardless, an increase in sexual frequency of one to 1 1/2 sex events per month hardly seems enough to warrant regular marijuana use. It certainly seems unlikely to increase the happiness we referenced earlier.

For starters, users can become dependent upon the drug, needing it before they have sex. Also, marijuana, like alcohol and other drugs, can lead to more promiscuous behavior, especially in younger adults. This can lead to intercourse with multiple partners and a failure to use condoms, raising the risk of sexually transmitted diseases.

So yes, marijuana use may lead to slightly more sex -- but also more risk.

(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 dad is 65 years old and has Type 2 diabetes. He recently developed pain in his feet, which his doctor says is peripheral neuropathy. What is that, and what treatments are available?

Dear Reader: Neuropathy is a condition in which the nervous system malfunctions due to either disease or some kind of damage. The addition of the word "peripheral" means the problem lies in the vast and complex network of nerves that serves the body.

The peripheral nervous system collects and sends vital sensory information to the central nervous system, which is made up of the brain and the spinal cord. When you drop that hot frying pan handle, break into a sweat on a hot day or keep your balance with your eyes closed, that's all thanks to information your peripheral nervous system has sent to your brain.

It's estimated that 20 million people in the United States experience some kind of peripheral neuropathy. Sometimes the damage is limited to a single nerve, but most often the condition affects groups of nerves. Symptoms include numbness, twitching, throbbing or tingling, burning sensations, problems with balance, or skin sensitivity so acute that ordinary stimuli, like the touch of a shirt on bare skin, are interpreted as pain.

When the motor nerves are affected, peripheral neuropathy causes muscle weakness and can often lead to the loss of muscle mass. If the nerves that serve the organs or glands are involved, it can result in impaired digestion, perspiration, urination or sexual function. At its most extreme, peripheral neuropathy causes breathing difficulties, or leads to organ failure. Fortunately, this is rare.

Diabetes is the most common cause of peripheral neuropathy. Other factors include infections such as shingles or the Epstein-Barr virus, certain kidney disorders, vitamin deficiencies, physical damage, cancers that press on or infiltrate nerve fibers, or autoimmune diseases that cause the body to attack its own tissues. Exposure to toxic industrial and environmental substances such as lead, arsenic or pesticides as well as medical agents like chemotherapy drugs can also lead to the condition. So can heavy alcohol consumption.

Your father's symptoms began in his feet, which is common among people with diabetes. He may also experience numbness, a decrease in foot and ankle reflexes, trouble with balance and coordination, and an increase in foot problems like ulcers and infections. This is due to tissue damage resulting from chronic high blood glucose levels, as well as decreased circulation, which occurs because diabetes causes the blood vessels in the foot and leg to become stiff and grow narrow.

Treatment for your father's condition will focus on two things -- carefully controlling his diabetes to prevent further nerve damage, and giving him relief from the existing pain. Mild pain often responds to over-the-counter NSAIDs. Medications like antidepressants, anticonvulsants and narcotics are used for chronic pain. Procedures like electrical nerve stimulation have shown promise. Physical therapy and specialized footwear can also help.

Pain treatment is often most effective when there's an ongoing dialogue. Be sure your dad shares all his symptoms with his doctor, and follows up with regular progress reports.

(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 Type A husband, who naturally falls asleep for about 25 minutes on weekend afternoons, complains that he's wasting time when he does so. How do I explain to him the benefits of napping?

Dear Reader: Millions of people throughout the world take a daily nap. In many cultures the afternoon sleep break is built right into everyday life. Businesses close shop and everyone heads home for lunch and a bit of shut-eye.

Here in the goal-oriented United States, though, napping carries a bit of stigma. It sounds as though your husband has internalized that feeling, which is too bad because you're correct -- a daytime nap is often a good thing.

Studies show that napping does more than just reduce fatigue. It can elevate your mood, improve productivity and make it easier for you to learn and retain new information.

However -- and this is where things get a bit tricky -- not all naps are equally beneficial. It turns out that what time you nap and how long that nap lasts make a difference.

A nap as brief as 10 minutes and up to 30 minutes can leave you feeling energized. Sleep much longer than half an hour and chances increase that you'll wake in a mental fog. The reason for all this is that sleep is quite complex. Not only are there several different stages of sleep, they occur in distinct cycles.

When you first drift off, you move from light sleep, from which you can awaken easily, into stages of ever-deeper sleep. Your brain waves and even your brain chemistry change. It becomes progressively more difficult to awaken. People in the stage known as "deep sleep" show no muscle or eye movement.

The other stage of sleep is known as REM sleep, which is short for "rapid eye movement." This is the cycle during which you dream, and in which the brain registers significant electrical and chemical activity. Fall short on REM sleep and it's quite possible you'll wind up feeling cranky or irritable.

Which leads us back to the question of optimal napping.

First -- what time to close your eyes. Sleep experts agree that mid-afternoon is optimal. Your body clock is naturally primed for a break, and it's far enough away from bedtime so as to not interfere with your night sleep.

Next, the reason why a brief nap feels best.

It takes about 90 minutes for your body (and brain) to go through a complete sleep cycle. Sleep too little and you've barely grazed the surface of light sleep. Sleep too long and you're swimming up from the groggy depths of deep sleep. Aim for 20 to 30 minutes, which puts you into the earliest stages of REM sleep and lets you wake up easily, feeling refreshed.

For the best naps, choose a location that's dark and quiet. Lying down results in better sleep than sitting or reclining. Setting an alarm will let you relax into your nap and assure that you'll wake up before deep sleep takes hold.

When you wake up, take a moment to stretch and take a few deep breaths. And enjoy. A good nap is one of life's real pleasures.

(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.)