DEAR DR. DONOHUE: I have had migraine headaches for years, but no one has ever told me how they come about. Please do. – W.B.

DEAR DR. DONOHUE: My mother has had migraines for years. Her doctor gave her a list of trigger foods, which include caffeine. If caffeine is a trigger, why is it included in many migraine medicines? – J.L.

ANSWER: A migraine headache is a torturous, pulsating, pounding headache on one side of the head that drives a migraineur (the medical word for migraine patient) to seek a dark, quiet retreat. Light and noise increase the pain of a migraine.

The cause of migraines is an overly sensitive nervous system. Numerous triggers – caffeine, anxiety, glaring lights, too much or too little sleep, cigarette smoke, changes in barometric pressure and foods such as avocados, wine and aged cheeses – can switch on a migraine headache. What happens is that a part of the brain called the migraine generator is activated, and it spreads noxious messages to the trigeminal nerve. That nerve is one of the principal nerves of the head and scalp. The nerve, in turn, releases materials that inflame head and scalp arteries, resulting in a throbbing migraine headache.

Caffeine is a trigger for some migraineurs. It’s included in some migraine medicines because it increases the painkilling properties of the medicine. It is usually in an amount much lower than the amount that causes migraine headaches.

Nowadays, those medicines have been largely supplanted by the more effective triptans: Imitrex, Zomig, Amerge, Maxalt and Relpax. They have revolutionized migraine treatment.

DEAR DR. DONOHUE: A friend and I believe a relative of mine is depressed. The person has no appetite, no interest in getting dressed and is in a constant funk. Weight loss is 40 pounds. Are we justified in feeling this person is depressed? The person refuses to discuss it. How do we approach the advisability of having this person see a doctor when the person considers it a taboo subject? – P.M.

ANSWER: You have summed up the symptoms of depression quite accurately. Depression makes people lose interest in things they used to view with joy. Their sleep is disturbed. Either they cannot fall asleep or they waken early in the morning and cannot get back to sleep. Depression drains its victims of all energy. They lose their appetite and lose weight. Their outlook on life is one of hopelessness.

Many depressed people, like your relative, are loath to talk about this subject, since they feel it represents a weakness of character. That is antediluvian thinking. It results from an imbalance of brain chemicals that keep people on an even emotional keel. Medicines and talk therapy can restore the brain’s chemical balance. Please tell your relative that precious time is being wasted by not seeking the help that is readily available to all.

DEAR DR. DONOHUE: I saw a newspaper article about smoking affecting the sexual performance of men. I was a firefighter and in 25 years have inhaled all kinds of toxic smoke. I am 65 and have been impotent for 15 years. Could the smoke I inhaled fighting fires have caused my impotence? – M.B.

ANSWER: Men who smoke 20 or more cigarettes a day run a 60 percent risk of suffering from erectile dysfunction.

I cannot find information that links noncigarette smoke to erectile dysfunction. That’s not to say it couldn’t, but only that the information is scanty to nonexistent.

Have you seen a doctor about the many new treatments for erectile dysfunction? Regardless of the smoke question, treatment might be readily available for you.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475.