One thing that always fascinates me is how reductionist, how mechanical, how sciencey and medical we like our stories about the body to be. This week, a new study was published on acupuncture. Many newspapers said it showed acupuncture performing better than medical treatment: in fact it was 8 million times more interesting than that.

They took 1,162 patients who had suffered with back pain for an average of eight years (so these were patients who had failed with medical treatment anyway) and divided them into three groups. The first group had some more medical treatment; the second had full-on acupuncture with all the trimmings, the needles all put carefully into the correct "meridians" and so on; while the third group just had some bloke pretending to be an acupuncturist, sticking needles in their skin at random.

The study set a threshold for "response to treatment", which was an improvement of 33% on three items out of a bigger scale, or 12% on one symptom scale. So this was not "getting better", or a "cure".

I'm not carping, I'm just telling you what they measured. And what were the results? Firstly, 27% of the medical treatment group improved: this is an impressive testament to the well-known healing power of simply "being in a trial", since medical treatment hadn't helped these patients for the preceding eight years. Meanwhile, 47% of the acupuncture group improved, but the sting is this: 44% of the fake acupuncture group improved too. There was no statistically significant difference between proper, genuine acupuncture and fake, "bung a needle in, anywhere you fancy, with a bit of theatrical ceremony" acupuncture.

There are three possible explanations for this finding. One is that sticking needles in your body at random helps back pain due to some physiological mechanism. The second is that theatrical ceremony, reassurance, the thought of someone doing something useful, helps back pain. (The third option is "a bit of both".)

Now as I have said so many times before, the placebo effect is not about a sugar pill, it's about the cultural meaning of a treatment, and our expectations: we know from research that two sugar pills are more effective than one, that a salt water injection is better for pain than a sugar pill, that colour and packaging have a beneficial effect, and so on.

Interestingly, there has even been a trial on patients with arm pain specifically comparing a placebo pill against a placebo ritual involving a sham medical device, modelled on acupuncture, which found that the elaborate ritual was more effective than the simple sugar pill. "Placebo" is not a unitary phenomenon; there is not "one type of placebo".

But the most important background information missing from the news reports wasn't about the details of the study: it was about back pain. Because back pain isn't like epilepsy or tuberculosis. Most of the big risk factors for a niggle turning into chronic longstanding back pain are personal, psychological, and social: things like depression, job dissatisfaction, unavailability of light duty on return to work, and so on.

And the evidence on treatments tells an even more interesting psychosocial story: sure, anti-inflammatory drugs are better than placebo. But more than that, bed rest is actively harmful, specific exercises can be too, and proper trial data shows that simply giving advice to "stay active" speeds recovery, reduces chronic disability, and reduces time off work.

We don't like solutions like that for our health problems. There are huge industries telling you that your tiredness is due to some "chromium deficiency" (buy the pill); your cloudy-headed feeling can be fixed with vitamin pills, pills, and more pills. It is a brave doctor who dares to bring up psychosocial issues for any complaint when a patient has been consistently told it is biomedical.

But in conditions like back pain or fatigue, information alone can make a difference. In Australia, a simple public information campaign ("Back pain: don't take it lying down", arf) was shown to reduce back pain significantly.

· Full academic references for these studies are at badscience.net