This week, Dr. Sydney Spiesel discusses genetic testing to figure out who is at risk of suicide while taking antidepressants, whether heart patients should take antibiotics before going to the dentist, and the appearance of lionfish in the Atlantic.
Problem: One of the most difficult and vexing problems that physicians deal with is depression. Over a lifetime, perhaps 10 percent of men and one-quarter of all women will have some experience with it. The illness leads to the majority of psychiatric hospitalizations (about 70 percent). The personal and social burden is huge. And while estimates vary, probably 40 percent to 60 percent of suicides are the result of depression.
Risk: The antidepressant medications that are commonly prescribed carry a now-familiar risk: There is evidence that sometimes, at least, the drugs increase the likelihood that patients will think about suicide and may attempt it. As a result of these findings, three years ago the FDA required that antidepressants contain a warning to doctors about the heightened risk of suicide for children and adolescents taking these medications.
New research: In the wake of the warnings, many doctors stopped prescribing these medications, or at least prescribed them less. And yet, according to a very recent study, the suicide rate did not fall. Robert Gibbons of the University of Illinois and his colleagues examined the epidemiology of suicide in the United States and in the Netherlands after the use of antidepressant medication for young people declined. They noted an increased risk of suicide in children and adolescents during this period. It is hard or impossible to prove causation using epidemiological data, but these findings must make us wonder, at least, about the link between antidepressants and suicide.
More new research: Maybe (as some of us have suspected for a long time) these medications decrease the risk of suicidal thinking or suicide attempts for most patients but increase it for a few. Is there a way to identify those few in advance? That is the promise of a tremendously exciting study by Dr. Gonzalo Laje of the National Institute for Mental Health and his co-workers, just published in the American Journal of Psychiatry. Using data collected for another study (the STAR*D trial), these researchers studied more than 1,800 patients suffering from a major depressive disorder who were treated with citalopram (Celexa), a commonly used antidepressant in the selective serotonin reuptake inhibitor class. The patients were divided into two groups: those who reported thinking about suicide despite treatment (120) and those who were free of suicidal thoughts (1,742). The team collected DNA and looked at how 68 genes thought to play some role in mood matched up with the presence or absence of suicidal thoughts. Two gene variants were correlated with suicidal thinking, and testing for them might well give us the ability to predict which patients are at special risk for suicide when they are treated with SSRI antidepressants.
Conclusion: If confirmed by later research, these results are of great interest. Theoretically speaking, if we understand the function of these aberrant genes, we are likely to learn a lot about the mechanism of clinical depression. And practically speaking, we could come up with a test that would allow us to distinguish between patients who can be safely treated with antidepressants and those who should not be given these medications. Such a tool would be enormously helpful. (And I notice that Laje's team has applied for such a patent.)
Reversal: For more than 50 years, cardiologists and infectious disease specialists have insisted that patients with many kinds of heart disease (including congenital heart problems, rheumatic heart disease, and mitral valve prolapse) receive a dose of an antibiotic before dental treatment or some kinds of surgery. Now, suddenly, new recommendations have reversed this protocol for the great majority of the people who were following them. More disturbingly, patients have been told that the former practice was probably unnecessary and possibly harmful.
Question: What's going on? The antibiotics were supposed to prevent patients from developing infective endocarditis (formerly called subacute bacterial endocarditis)—a bacterial infection of the lining of the heart that was always fatal in the days before antibiotics. This infection is rare, but the numbers are greater in some groups, including intravenous drug abusers, patients born with structural heart abnormalities, and patients with heart damage following rheumatic heart disease.
Illness: Infective endocarditis is thought to stem from abnormal patterns of blood flow, which lead to a roughening of the otherwise smooth surface of the heart lining. Blood clots form and attach to these roughened sites. Then bacteria present in the bloodstream attach to the blood clots and start to multiply and infect the heart's lining. Bacteria enter the bloodstream when mucous membrane tissues (like the surface of gums or the lining of the bowel) are disturbed. This happens at the dentist, when teeth are extracted or cleaned, or during gastrointestinal surgery. And the same species of bacteria often found in the crevices around teeth are a common cause of infective endocarditis.
Old treatment: In animal experiments, antibiotic administration was shown to effectively prevent infective endocarditis. So it just seemed reasonable to give human patients a brief blast of an antibiotic as they went in for dental work. But a great deal of research failed to show that this pretreatment was actually useful. In fact, a fine piece of research done almost 10 years ago by Dr. Brian Strom of the University of Pennsylvania showed that dental treatment didn't pose a risk for this disease, even in patients with a strong predisposition to develop it as a result of heart abnormalities.
New thinking: The old recommendations were abandoned for several reasons. First, worthless use of antibiotics invites the development of antibiotic resistance in bacteria—and we already have enough of that, thank you. Second, every time you take an antibiotic, useless or not, you risk developing a medication allergy or allergic reaction.
Conclusion: Yet, old habits die hard. Many of my colleagues tell me that it is very difficult to convince their patients that a treatment to which they were accustomed was for naught. Paradoxically, a triumph of modern medicine—leaving behind a useless and perhaps harmful old practice as a result of new research—proves to be profoundly disturbing.
Risk: Much of the time, the risks we most fear have little do with our real lives. For that reason, I am always reluctant to worry people about some exotic danger they're unlikely to ever encounter. But this one is too good to pass up.
Here they come: A letter to the editor in last week's Freeport News (Freeport as in the Bahamas) described the appearance of the lionfish in the Atlantic. Expert Paul Auerbach has taught me about this exotic, extraordinarily beautiful but quite dangerous fish. Its natural habitats are the tropical waters around Malaysia and Australia, and other parts of the Pacific. But now lionfish are being collected in ever-increasing numbers along the Atlantic coast of the United States, from the waters around Long Island through the Carolinas and Florida. The first hard evidence dates from 2000, in the Carolinas. Probably, some pet owner tired of managing a tank full of these dangerous tropical fish just dumped them overboard.
Harm: Lionfish are zebra-striped, brightly colored, and sport a "mane" of flashy pectoral fin elements. The fish has other fins with spines, some of which are equipped with poison glands. Their sting is apparently hideously painful and even sometimes—if rarely—fatal. The treatment is relatively simple: immersion of the affected body part in hot (though not scalding) water for half an hour or so. Despite the danger, the fish are often sold for salt-water aquariums, without a caveat emptor. If you have some you don't want, they're edible. And if that's not appealing, whatever you do, don't send them off to take over a beach near you.