Previously I wrote about a small study finding that smoked marijuana helps with HIV-related pain. In the last month, two more clinical trials of medical marijuana - or rather, marijuana-based drugs - for pain have come out.

First, the good news. Johnson et al tested a mouth spray containing the two major psychoactive chemicals in marijuana, THC and CBD. Their patients were all suffering from terminal cancer, which believe it or not, is quite painful. Almost all of the subjects were already taking high doses of strong opiate painkillers: a mean of 270 mg morphine or equivalent each day, which is enough to kill someone without a tolerance. (A couple of them were on an eye-watering 6 grams daily). Yet they were still in pain.

Patients were allowed to use the cannabinoid spray as often as they wanted for 2 weeks. Lo and behold, the THC/CBD spray was more effective than an inactive placebo spray at relieving pain. The effect was modest, but statistically significant, and given what these people were going through I'm sure they were glad of even "modest" effects. A third group got a spray containing only THC, and this was less effective than the combined THC/CBD - on most measures, it was no better than placebo. THC is often thought of as the single "active ingredient" in marijuana, but this suggests that there's more to it than that. This was a relatively large study - 177 patients in total - so the results are pretty convincing, although you should know that it was funded and sponsored by GW Pharma, whose "vision is to the global leader in prescription cannabinoid medicines". Hmm.

Jamie Talan's Deep Brain Stimulation: A New Treatment Shows Promise In The Most Difficult Cases is the first book to offer a popular look at DBS, one of the more exciting emerging treatments in neurology and psychiatry.

Deep Brain Stimulation is not a textbook and the depth of scientific detail is kept pretty low, but the breadth of the material is good. Talan reviews the many kinds of disorders for which DBS has been trialled, from the early 1990s when it was used in Parkinson's disease up to the past five years where it's been tried for everything from epilepsy, depression and Tourette's Syndrome up to lifting patients out of persistent vegetative states (maybe).

Unfortunately, Talan doesn't discuss the controversial history of the first era of human brain stimulation, including the morally murky work of Robert G. Heath at Tulane University in the 1960s. She mentions Tulane once in passing but more detail would have been welcome, if only because it's a rather spicy tale.

The book's most engaging passages are the stories of individual patients. There's the man with Parkinson's who experienced amazing benefits from DBS, and who was so keen to keep them that he didn't tell doctors about the infection which developed a few weeks after surgery, in case they took the electrode out. After literally keeping the infected site under his hat for a few days, it progressed to a brain abscess, and he nearly died. Happily, he not only survived but was able to get the electrodes reimplanted.

Then there's the most moving case, that of the woman suffering from severe OCD and depression, who was given experimental DBS for the former condition. She died by suicide several months later, but said in her suicide note that the DBS had worked - her OCD symptoms were gone. Her depression was as bad as ever, though, and this is what led her to suicide. She wanted people to know that deep brain stimulation helped her, and didn't want her death to go down in the records as a mark against it.

The precursor to DBS was ablative neurosurgery - destroying particular parts of the brain in order to relieve symptoms. Talan describes its use in movement disorders such as Parkinson's, but she glosses over the history of "psychosurgery", the use of surgery to treat mental illness. People using DBS in psychiatry often prefer not to talk about psychosurgery - it's not exactly good PR. But clearly it is relevant. For all its faults, psychosurgery did seem to help some patients, which is why it's still used today in rare cases, although DBS may soon replace it.

DBS for depression and OCD usually target the same prefrontal white matter pathways that psychosurgery severed, so scientifically, psychosurgery has lessons for DBS. The ethical issues overlap too. Although DBS is reversible, unlike brain lesioning, it carries the same risks of serious complications like infection or brain bleeding. And there's the same question of whether seriously mentally ill people can give informed consent.

The book's strongest chaper is the last, which covers the ethical and practical difficulties of DBS. The danger is that enthusiastic doctors with no experience of the procedure, encouraged by the tales from other hospitals, might start doing it inappropriately. There's also a risk that patients or their families might volunteer for DBS prematurely or have impossibly high expectations. The initial results have been very promising, but there have been no large placebo-controlled trials so far (except in some movement disorders). And even with the best surgeons, in most disorders the response rate seems to hover around the 50-60% mark. Talan warns that DBS risks being a victim of its own hype. That's an important message.

You may already have heard about Desiree Jennings.

In a matter of a few short weeks I lost the ability to walk, talk normally, and focus on more than one stimuli at a time. Whenever I eat I know, without fail, that my body will soon go into uncontrollable convulsions coupled with periods of blacking out.

I predict that they will be able to “cure” her, because psychogenic disorders can and do spontaneously resolve. They will then claim victory for their quackery in curing a (non-existent) vaccine injury.

People seem more willing to accept the mind-over-matter powers of "the placebo" than they are to accept the existence of psychosomatic illness.

It's always nice when a local boy makes good in the big wide world. Many British neuroscientists and psychiatrists have been feeling rather proud this week following the enormous amount of attention given to Professor David Nutt, formerly the British government's chief adviser on illegal drugs.

Formerly being the key word. Nutt was sacked (...write your own "nutsack" pun if you must) last Friday, prompting a remarkable amount of condemnation. Critics included the rest of his former organisation, the Advisory Council on the Misuse of Drugs (ACMD), and the Government's Science Minister. The UK's Chief Scientist also spoke in favour of Nutt's views. Journalists joined in the fun with headlines like "politicians are intoxicated by cowardice".

"The sacking of a government adviser on drugs shows Britain's politicians can't cope with intelligent debate... the position of the Labour government and of the leading opposition party, the Conservatives, which vigorously supported Nutt's sacking, has no merit at all. It deals a significant blow both to the chances of an informed and reasoned debate over illegal drugs, and to the parties' own scientific credibility."

"Where there is a clear and serious problem [i.e. cannabis health problems], but doubt about the potential harm that will be caused, we must err on the side of caution and protect the public. I make no apology for that. I am not prepared to wait and see."

"the precautionary principle - if you’re not sure about a drug harm, rank it high... at first sight it might seem the obvious decision – why wouldn’t you take the precautionary principle? We know that drugs are harmful and that you can never evaluate a drug over the lifetime of a whole population, so we can never know whether, at some point in the future, a drug might lead to or cause more harm than it did early in its use."

Coffee contains caffeine, and as everyone knows, caffeine is a stimulant. We all know how a good cup of coffee wakes you up, makes you more alert, and helps you concentrate - thanks to caffeine.


Or does it? Are the benefits of coffee really due to the caffeine, or are there placebo effects at work? Numerous experiments have tried to answer this question, but a paper published today goes into more detail than most. (It caught my eye just as I was taking my first sip this morning, so I had to blog about it.)

The authors took 60 coffee-loving volunteers and gave them either placebo decaffeinated coffee, or coffee containing 280 mg caffeine. That's quite a lot, roughly equivalent to three normal cups. 30 minutes later, they attempted a difficult button-pressing task requiring concentration and sustained effort, plus a task involving mashing buttons as fast as possible for a minute.

The catch was that the experimenters lied to the volunteers. Everyone was told that they were getting real coffee. Half of them were told that the coffee would enhance their performance on the tasks, while the other half were told it would impair it. If the placebo effect was at work, these misleading instructions should have affected how the volunteers felt and acted.

Several interesting things happened. First, the caffeine enhanced performance on the cognitive tasks - it wasn't just a placebo effect. Bear in mind, though, that these people were all regular coffee drinkers who hadn't drunk any caffeine that day. The benefit could have been a reversal of caffeine withdrawl symptoms.

Second, there was a small effect of expectancy on task performance in the placebo group - but it worked in reverse. People who were told that the coffee would make them do worse actually did better than those who expected the coffee to help them. Presumably, this is because they put in extra effort to try to overcome the supposedly negative effects. This paradoxical placebo response reminds us that there's more to "the placebo effect" than meets the eye.

Finally, no-one who got the decaf noticed that it didn't actually contain caffeine, and the volunteer's ratings of their alertness and mood didn't differ between the caffeine and placebo groups. So, this suggests that if you were to secretly replace someone's favorite blend with decaf, they wouldn't notice - although their performance would nevertheless decline. Bear that in mind when considering pranks to play on colleagues or flatmates.

It looks like science has just confirmed another piece of The Wisdom of Seinfeld:

Elaine: Jerry likes Morning Thunder.
George: Jerry drinks Morning Thunder? Morning Thunder has caffeine in it. Jerry doesn't drink caffeine.
Elaine: Jerry doesn't know Morning Thunder has caffeine in it.
George: You don't tell him?
Elaine: No. And you should see him. Man, he gets all hyper, he doesn't even know why! He loves it. He walks around going, "God, I feel great!"
- Seinfeld, "The Dog"

Six months ago, I asked What's The Best Antidepressant?, and I discussed a paper by Andrea Cipriani et al. The paper claimed that of the modern antidepressants, escitalopram (Lexapro) and sertraline (Zoloft) offer the best combination of effectiveness and mild side effects, and that sertraline has the advantage of being much cheaper.

The Cipriani paper was a meta-analysis of trials comparing one drug against another. With a total of over 25,000 patients, it boasted an impressively large dataset, but I advised caution. Their method of crunching the numbers (indirect comparisons) was complex, and rested on a lot of assumptions.

I wasn't the only skeptic. Cipriani et al has attracted plenty of comments in the medical literature, and they make for some fascinating reading. Indeed, they amount to crash-course in the controversies surrounding antidepressants today - a whole debate in microcosm. So here's the microcosm, in a nutshell:

Free of any potential funding bias... Now, the clinician can identify the four best treatments... A new gold standard of reliable information has been compiled for patients to review.

documents that a communications agency acting on behalf of the makers of sertraline were forced to make available by a US court. Among them was a register of completed sertraline studies awaiting to be assigned to authors. This practice (rent-a-key-opinion-leader) is of unknown prevalence but it undermines any attempt at reviewing the evidence in a meaningful way.

Among placebo controlled antidepressant trials registered with the US FDA, most negative results are unpublished or published as positive. Take sertraline, which Cipriani and colleagues recommend as the best ... of five FDA-registered trials, the only positive trial was published, one negative trial was published as positive, and three negative trials were unpublished. Head-to-head comparisons can suffer worse bias, since regulatory registration is uncommon. Meta-analysis of published plus industry-furnished data could spuriously suggest that the best drugs are those with the most shamelessly biased data ...

we contacted the original authors and pharmaceutical companies to obtain further data or to confirm reported figures.

The standard thinking has become that most antidepressants are of similar average efficacy and tolerability ... In some ways, this is a comfortable position for industry and its hired academic opinion leaders—it sets a low threshold for the introduction of new agents which can initially be marketed on the basis of small differences in specific adverse effects rather than on clear advantages in terms of overall average efficacy and acceptability.

Ranking sertraline and escitalopram higher than other drugs conveys a precision
and existence of clinically important differences that is not reflected in the body of evidence. ...for sertraline and escitalopram the range of probabilities actually extends from the first to the eighth rank for both efficacy and acceptability... the validity of results of indirect comparisons depends on various assumptions, some of which are unverifiable ... We simply took underlying uncertainties into greater consideration and interpreted findings more cautiously than Cipriani and colleagues.

they included studies with very different populations such as frail elderly, patients with accompanying anxiety and inpatients as well as outpatients ... the effect measure of choice was odds ratios rather than relative risks. Odds ratios have mathematical advantages that statisticians value. Practitioners, however, frequently overestimate their clinical importance...

We have a choice. We may either make the best use of the available randomised evidence or we essentially ignore it. We believe that it is better to have a set of criteria based on the available evidence than to have no criteria at all... We believe that, despite the likely biases of the included trials, and the limitations of our approach, our analysis makes the best use of the randomised evidence, providing clinicians with evidence based criteria that can be used to guide treatment choices.

Deep-brain stimulation (DBS) is probably the most exciting emerging treatment in psychiatry. DBS is the use of high-frequency electrical current to alter the function of specific areas of the brain. Originally developed for Parkinson's disease, over the past five years DBS has been used experimentally in severe clinical depression, OCD, Tourette's syndrome, alcoholism, and more.

Reports of the effects have frequently been remarkable, but there have been few scientifically rigorous studies, and the number of psychiatric patients treated to date is just dozens. So the true usefulness of the technique is unclear. How DBS works is also a mystery. Even the most basic questions - such as whether high-frequency stimulation switches the brain "on" or "off" - are still being debated.

Recent data from rodents sheds some important light on the issue: Antidepressant-Like Effects of Medial Prefrontal Cortex Deep Brain Stimulation in Rats. The authors took rats, and implanted DBS electrodes in the infralimbic cortex. This area is part of the vmPFC. It's believed to be the rat equivalent of the human region BA25, the subgenual cingulate cortex, which is the most common target for DBS in depression. The current settings (100 microA, 130 Hz, 90 microsec) were chosen to be similar to the ones used in humans.

In a standard rat model of depression, the forced-swim test, infralimbic DBS exerted antidepressant-like effects. DBS was equally as effective as imipramine, a potent antidepressant, in terms of reducing "depression-like" behaviours, namely immobility.

This is not all that surprising. Almost everything which treats depression in humans also reduces immobility in this test (along with few things which don't treat it). Much more interesting is what did and did not block the effects of DBS in these rats.

First off, DBS worked even when the rat's infralimbic cortex had been destroyed by the toxin ibotenic acid. This strongly suggests that DBS does not work simply by activating the infralimbic cortex, even though this is where the electrodes were implanted.

Crucially, infralimbic lesions did not have an antidepressant effect per se, which also rules out the theory that DBS works by inactivating this region. (Infralimbic lesions produced by other methods did have a mild antidepressant effect, but it was smaller than the effect of DBS. This may still be important, however.)

What did block the effects of DBS was the depletion of serotonin (5HT). Serotonin is known to its friends as the brain's "happy chemical", although it's a bit more complicated than that. Most antidepressants target serotonin. And rats whose serotonin systems had been lesioned got no benefit from DBS in this study.

So this suggests that DBS might work by affecting serotonin, and indeed, DBS turned out to greatly increase serotonin release, even in a distant part of the brain (the hippocampus). Interestingly this lasted for nearly two hours after the electrodes were switched off.

Depletion of another neurotransmitter, noradrenaline, did not alter the effects of DBS.

Overall, it seems that infralimbic DBS works by increasing serotonin release, but that this is not because it activates or inactivates the infralimbic cortex itself. Rather, nearby structures must be involved. The most likely explanation is that DBS affects nearby white-matter tracts carrying signals between other areas of the brain; the infralimbic cortex might just happen to be "by the roadside". Many researchers believe that this is how DBS works in humans, but this is the first hard evidence for this.

Of course, evidence from rats is never all that hard when it comes to human mental illness. We need to know whether the same thing is true in people. As luck would have it, you can temporarily reduce human serotonin levels with a technique called acute tryptophan depletion This reverses the effects of antidepressants in many people. If this rat data is right, it should also temporarily reverse the benefits of DBS. Someone should do this experiment as soon as possible - I'd like to do it myself, but I'm British, and all the DBS research happens in America. Bah, humbug, old bean.

There's a couple of others things to note here. In other behavioural tests, infralimbic DBS also had antidepressant-like effects: it seemed to reduce anxiety, and it made rats more resistant to the stress of having electrical shocks (although only slightly.) Finally, DBS in another region, the striatum, had no antidepressant effect at all. That's a bit odd because DBS of the striatum does seem to treat depression in humans - but the part of the striatum targeted here, the caudate-putamen, is quite separate to the one targeted in human depression, the nucleus accumbens.

Hamani, C., Diwan, M., Macedo, C., Brandão, M., Shumake, J., Gonzalez-Lima, F., Raymond, R., Lozano, A., Fletcher, P., & Nobrega, J. (2009). Antidepressant-Like Effects of Medial Prefrontal Cortex Deep Brain Stimulation in Rats Biological Psychiatry DOI: 10.1016/j.biopsych.2009.08.025