Oh, I wouldn't say that. The candidates nowadays must take a Wonderlic test, a Minnesota Multiphasic Personality Inventory, a Test of Adult Basic Education (Level A), and maybe one or two others.
The Wonderlic is an IQ test, full stop: it weeds out the dummies, nothing more. (It is a backup for the GT score (IQ) minumum standard). The MMPI is a personality test that produces several scales indicating where in a range of several personality traits a person finds himself. It is uncannily valid, and can catch people trying to fake the test. So it weeds out some of the quitters, glory seekers and personality disorders (pity they didn't have it when 'Jack' Idema joined up). The TABE just tests basic knowledge: it weeds out the ignorant, the very poorly educated, and those that have learning problems.
When I joined up they didn't have all these tests; instead you had to get a "crazy statement" from the crazy doctor that you were not a nutball. (This is still required for certain types of advanced training today, about which the less said the better). My "crazy doctor" was an AF Pshrink who was absolutely appalled to find himself in the presence of someone who would want to go, in his words, "running off killing snakes and eating people." When I explained that it was eating snakes and killing people, he reluctantly signed the statement for me.
Now, today's regime is certainly more comprehensive than that, and it's more than what other parts of the military do to people who are, mostly, already in the service with good records; but it's far from infallible.
Plus, any psychological test or review is a snapshot of a moment in time. I think most of us can, from our own experience as friends, supervisors, etc., attest to the power of (for instance) a love affair, especially in the throes of starting or ending, to screw up even an orderly and disciplined life.
Right now, malaria prophylaxis is saving American lives. (All the main theaters of the GWOT are in malaria season this very minute). That doesn't mean we can't learn from study, but I want to remind everybody that the decision when the best scientific evidence is in may well be, to take the hits we take from mefloquine psychosis (the literature online says 1 in 15,000 or 20,000 users, which is a VERY high level of such a serious side effect), rather than risk the hits that malaria will give us.
d.o.l.
Criminal Number 18F
I guess I ought to read up more on malaria and its severity. I had it twice before age 5 (living in Rwanda) and don't seem to have suffered any ill effects, so I don't think of it as a big killer -- though I hear it is, at least among the native populations of 3rd World countries who don't have access to high quality medical care.
The weird thing is how the suicides and homicides seem to be heavily concentrated among Special Forces, when 1) lots of other servicepeople are taking this drug (along with other drugs, vaccines, etc.) and 2) they are psychologically screened to a higher level than most other military units. Sure they've got more stressful missions, but that's always been the case, and I don't recall hearing about rashes of suicides or homicides among them in the past.