After another wave on my facebook feed of shared articles expressing concern, derision, and even outright fear over the diagnostic criteria given in the Diagnostic and Statistical Manual of Mental Disorders (DSM), currently in its fifth edition, I feel the need to write a little something here.

The DSM is essentially not much more than a means of linking a set of pathological traits with a shorthand definition. This can be useful when communicating between different health professionals or to health insurance companies, and when gathering statistics and conducting research on mental illness. It doesn’t generate new diseases, really, just labels to quickly describe observed illnesses.

The DSM itself explains that for something to be a mental illness, well, it has to cause illness — it needs to be “associated with present distress[…]or disability[…]or with a significant increased risk of suffering.”
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Word of the Day: Degenerate

There are many words which take a very different meaning in their scientific context to what they might mean in everyday use.

One that can cause a little bit of shock, then perhaps a giggle, is “degenerate”, used as an adjective.

Usually when you call someone or something degenerate, you are being insulting. It has connotations of stupidity, inferiority, degredation. In science, it can be much more innocent.

If you’re in physics or chemistry class and a pair or set of things get called “degenerate”, all it means is that they have the same amount of energy. So, there’s nothing wrong with a pair of degenerate electrons, they are just two electrons hanging out with the same energy.

Word of the Day: Massive

There are many words which take a very different meaning in their scientific context to what they might mean in everyday use.

One which always amuses me a little is “massive”.

Normally, when you call something massive, you mean it’s really rather large. You might look at me in bemusement if I call an electron “massive”. You may wonder what on earth an electron is big compared to. (The answer to that is: nothing, really. The electron is generally considered to be a point particle.)

What I actually mean is that the electron has mass. An electron is massive. An atom is You are massive. A photon is massless.

Massive: it doesn’t have to be big, it just has to have a non-zero mass.

It’s a Bird, It’s a Plane…

A contrail over southwest Virginia, 19 March 2012, captured by Eric T Gunther. Via http://en.wikipedia.org/wiki/File:Con_Trail_Virginia.JPG

A contrail over southwest Virginia, 19 March 2012, captured by Eric T Gunther. Via http://en.wikipedia.org/wiki/File:Con_Trail_Virginia.JPG

Contrails are a type of narrow, long cloud that can be caused by aircraft travelling through the cold air at high altitudes. They are caused either by condensation of water vapor from the engine exhaust as it is ejected into the cold air, or by condensation of water vapor already in the air around pressure changes due to vortices formed as air passes over the aircraft’s wing. Next time you are in a plane, if you can see a wing have a look; you might be able to see narrow vortices forming over the wing. It’s quite a dramatic sight! Depending on the altitude and conditions, they can appear as a short smudge or as a long, thin cloud stretching far across the sky.

When they form in the early morning or late evening, contrails can be mistaken for meteors, especially when the light catches them and can make them appear orange or golden. To tell the difference, look at them as they form. Is its leading end moving at a speed an aircraft might be able to move at? If it is, it’s an aircraft contrail. Meteors are fast. Does the leading end have an intensely bright fireball whose brightness varies in intensity? Meteor; we at least hope that aircraft aren’t bright, flickering fireballs!

In the News: Multivitamins and Other Supplements

In the news over the last couple of days there has been a certain amount of excitement over an editorial in the Annals of Internal Medicine accompanying a set of articles which, some outlets and blogs are claiming, show that “doctors say supplements don’t work and that you shouldn’t bother taking them. Ever.”

There is a huge amount of evidence that daily multivitamins are simply unhelpful and generally the “nutrition gaps” that their marketers claim to be plugging just don’t exist in the general population. (Possible exceptions include vitamin D and omega-3’s, talk to your doctor if you are concerned about these.) Vitamins and oral chelation therapy can most certainly cause harm, for the same reasons they can help when used in appropriate circumstances at appropriate doses.

You probably don’t take preventative paracetamol (tylenol) every day; you take it when the need arises. You wouldn’t get yourself monthly preventative blood transfusions; you’d only do that when you actually needed the blood product. It’d be wasteful and potentially harmful to do either of these things, but they would help you greatly if you were in a situation where you actually needed either of them.

The same goes for vitamins. They will help you… if you have a shortage of that particular natural chemical in your body. If you don’t, at best you’re wasting money, at worst, you’re putting too much in and will make yourself unwell. For example, if you have more vitamin A than you need, it can cause problems like hair loss and bone fractures. Excess vitamin C may elevate your risk of kidney stones. But a deficiency of vitamin A can cause serious vision problems, and vitamin C deficiency causes scurvy. (Yes, that thing pirates talk about; it’s entirely real, and quite nasty.)

The Annals of Internal Medicine does not deny this; those guys know what they’re on about. However, a proportion of other media outlets seem to have misunderstood what was being said.

Vitamin supplements, in appropriate doses and under appropriate circumstances, work.

Taking random vitamin cocktails (read: taking multivitamins, the thing that the article actually deals with) as part of your daily routine does not help anything, and may even give negative health outcomes.

If you have been diagnosed with low or deficient levels of a vitamin or mineral, use supplements as directed by your doctor. They are great for that.

If you THINK you might have low or deficient levels of a vitamin or mineral, speak to your doctor.

Nutrition is part of medicine. As with any other disease, if you think you have a nutritional deficiency that may need supplementation to correct, speak to your doctor or specialist dietician. If you don’t, you may be wasting your money, or you may even be doing yourself serious harm.

Word of the Day: Law

There are many words which take a very different meaning in their scientific context to what they might mean in everyday use.

Among these is “law”. When we talk about a law of science, we don’t mean “one of the strongest rules of science”. A law is simply a (often mathematical) description of something that happens. The law of conservation of energy (or mass-energy for those who are learning about mass-energy equivalence) is: “energy cannot be created or destroyed, only transformed.” Mathematically you can write that same thing as

ΔE = 0

It doesn’t tell you how the energy is conserved or transformed or anything, just that it is. (You’d need a theory to explain the mechanism!)

Laws can be changed. Laws can break down or fail to apply under particular unforseen circumstances. For example, Newton’s Laws of Motion are incorrect when you start comparing things moving close to the speed of light relative to each other, but they are still laws… they just don’t apply under some circumstances.

Principles serve the same purpose as laws; for example, Archimedes’ Principle, or The Principle of Least Action.

Word of the Day: Theory

There are many words which take a very different meaning in their scientific context to what they might mean in everyday use.

One such word that causes an awful lot of confusion is “theory”. As in, “theory of plate tectonics” or “theory of quantum electrodynamics“, but also as in “it’s just a theory, but…”

When people talk about having a theory in everyday language, usually they mean a hypothesis with very little evidence to back it up. A hunch, a feeling, a guess, an idea.

In science, a theory actually falls at entirely the other end of the spectrum. A theory is an explanation of the mechanism of how an observed phenomenon comes about which is strongly supported by empirical evidence.

A theory is different from a law not in the strength of it’s evidence, but in what it tells you. A theory deals with the mechanism behind a phenomenon. A law describes a phenomenon without dealing with how it comes about. If you like, a theory is an explanation, a law is a description.

This distinction causes a lot of confusion when it comes to the theory of evolution by natural selection. Evolution as a process is an observed phenomenon, not a theory. It can be seen in the lab. It can be exploited through deliberate selection by humans to create and modify domestic animal breeds. The theory part — the part that describes the mechanism — is “by natural selection.” To talk about the “theory of evolution” is to use a shorthand for the actual theory, compounding the confusion caused by not knowing the different scientific meaning of the word “theory”.