Dear Doctor: A relative long ago diagnosed with atrial fibrillation has been behaving differently, such as sitting with his mouth gaping open, not attending to financial matters, taking too long to do errands, that kind of thing. Could silent TIAs be the culprit?

Dear Reader: Yes, they could. First, let's explain atrial fibrillation. Two chambers known as atria make up the top portion of the heart, storing blood before it goes into the two bottom chambers, known as ventricles. The atria contract first, then the ventricles, setting the overall rhythm of the heart. In atrial fibrillation, the atria are damaged or enlarged and don't contract sufficiently or rhythmically. Because of this, some blood can stay within them, leading to a clotting of blood in this portion of the heart.

If the atria contract normally or the clot mobilizes for some other reason, then the clot can move into the ventricles, where it can then shoot into the circulatory system when the ventricles contract. The clot can then become lodged in the smaller blood vessels of the brain, leading to lack of blood flow to that area. The result is either a transient ischemic attack (TIA), in which a portion of the brain loses function for a short period, or a full-fledged stroke.

Atrial fibrillation could indeed be leading to small strokes in your relative. Often, these small strokes are not noted by the patient or by family members. A study in elderly residents in Germany found that 12.7 percent of them had experienced what's known as "silent strokes." Such strokes don't have obvious symptoms; instead, they can manifest as a difficulty in performing cognitive tasks or a slowing in everyday activities. Your relative's risk of strokes linked to atrial fibrillation would be lower if he has been taking blood thinners, but they still could occur.

A CT scan or MRI can easily determine whether your relative has had these silent strokes. It's important to get such a diagnosis because if his symptoms are related to a small stroke, he'll be at greater risk of having a large, debilitating stroke.

His symptoms could be linked to another type of stroke as well -- a lacunar stroke caused by very high blood pressure and diabetes, which lead to a narrowing of smaller blood vessels in the brain. These strokes can cause loss of function in a limb or the problems traditionally found in silent strokes.

Whether caused by atrial fibrillation or a narrowing of blood vessels, multiple strokes can lead to dementia, which also may be the reason for your relative's recent behavior. Alzheimer's disease, Lewy body dementia and normal pressure hydrocephalus also can cause the symptoms you describe, and imaging of the brain and a consultation with a neurologist can confirm these diagnoses.

Let's not forget another cause: depression. Depression in the elderly can have many of the same symptoms as dementia, causing difficulty in focusing on tasks, memory and self-care. Lastly, if the symptoms in your relative developed suddenly, infection could be the culprit.

In short, your relative's symptoms have many possible causes. But you're astute in thinking that TIAs or silent strokes due to atrial fibrillation may be to blame. Please encourage him and his closest family member to see a doctor; he obviously needs medical attention and recommendations specific to his needs.

(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 just had my first baby, and I'm breastfeeding him. I really enjoy the experience, and our pediatrician says he's hitting his weight milestones. But my mother-in-law is afraid he's not getting enough nutrients and is pressuring me to switch to formula. How do I know if my newborn is getting enough breast milk?

Dear Reader: Congratulations on your new baby and on the good reports from your pediatrician. We hope we can help you quiet your mother-in-law's concerns.

If you're healthy and are eating a balanced diet, then your breast milk has everything your baby needs to grow and thrive. It contains protein, fat, carbohydrates, vitamins, minerals and water for hydration. Breast milk is also a rich source of bioactive compounds that help strengthen your baby's brand-new immune system.

When your son nurses, he's taking in a remarkable food source that, in addition to being easily digested, helps him to absorb the nutrients that it contains.

It's not unusual to wonder whether your baby is getting adequate nutrition. We live in a world of food pyramids and portion sizes. Food and the nutrients it contains have become things that we measure down to the last ounce, gram and calorie. So the process of feeding an infant from one's own body, where it's hard to quantify exactly what and how much a baby is getting, can cause anxiety.

Your pediatrician's reassurance that your baby's weight is on target means he is getting the nourishment he needs. There are also some solid useful hallmarks that indicate whether things are going well.

In the first four or five days after birth, you should be getting four to six wet diapers per day. Babies who are well-hydrated will have pale or clear urine. If the baby's urine turns deep yellow or orange, like the color of apple juice or weak tea, it's a sign that he's not getting enough milk to support hydration.

How much stool a baby produces is another sign of how well breastfeeding is going. Within the first month, breastfed babies will be producing two or three bowel movements per day. Some, because breast milk can act as a natural laxative, may have a bowel movement with each feeding. After that, as the bioactive compounds we mentioned earlier help the baby's gut to mature, you'll notice that the number of bowel movements drops to about one (and occasionally fewer) per day.

With their tiny stomachs (at birth, a baby's tummy can hold about a teaspoonful or 2), newborns need to eat frequently. At 10 days old, they can comfortably hold up to 2 ounces. Newborns need to feed every two to three hours. As they get older, the frequency drops, and each baby will develop her or his own feeding pattern.

Being a new mother is challenging enough. Having a family member add to your worries makes things even harder. Perhaps introducing your mother-in-law to the excellent information available at womenshealth.gov (enter the word "breastfeeding" into the search box) can help calm her fears.

(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: 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.)