BBC website reports that, "'Green' exercise quickly 'boosts mental health'"

The BBC (and other sites) are reporting a study that apparently claims that "'Green' exercise quickly 'boosts mental health'". The study has been picked up by the US National post, and the UK Daily Mail.

The authors were Jo Barton and Jules Pretty (personal page at University of Essex here) and the study was published in the Environmental Science and Technology journal.

There are some bold claims, such as:

1. "The biggest effect was seen within just five minutes."
2. "A bigger effect was seen with exercise in an area that also contained water - such as a lake or river."

The paper can be found here (Abstract only | subscription required for full paper).

The authors state: "The research used meta-analysis methodology to analyze 10 UK studies involving 1252 participants." It doesn't say that it was a meta-analysis, only that it used the methodology (sic) of meta-analysis. Of course, you can only really meta-analyse studies with a degree of homogeneity and the conclusions one can draw from such reviews depend greatly on the quality of the underlying studies. Poorly-controlled and heterogenous studies with wild estimates of effect sizes don't lend themselves to robust systematic review.

Another alarm bell starts ringing when one reads, "Outcomes were identified through a priori subgroup analyses". Okay, the sub-groups were determined a priori, but subgroup analysis is often used as a way of mining the data for some significant finding. The BMJ has a recent article on the credibility of subgroup analyses.


It's surprising that the study also reported, "Dose responses for both intensity and duration showed large benefits from short engagements in green exercise, and then diminishing but still positive returns." This is counter-intuitive. If exercise is so good, why does it get less effective the more you do of it? I doubt the included studies were looking at elite athletes who may have been overtraining - the authors are reporting that more exercise is less beneficial for most of the reported outcomes (e.g. self-esteem).

It's clear that Jules Pretty is favourably disposed to exercise in green environments (who wouldn't be?), but previous 'reviews' would indicate that reported benefits in different studies are taken at face value, and not critically appraised in the way that they should be. For example, many studies in exercise for depression look at those with mild depressive illness which is, for many people, a self-limiting condition. The fact that someone feels better after a six-week course of exercise may have little to do with the exercise per se, and more to do with the natural course of the illness.

The 2009 Cochrane Review of Exercise for Depression concluded: "Exercise seems to improve depressive symptoms in people with a diagnosis of depression, but when only methodologically robust trials are included, the effect sizes are only moderate and not statistically significant." Essentially, when you exclude poorly-conducted trials, the effects of exercise are not statistically different from those that you would see with chance alone.

The availability of pornography in NHS fertility clinics

An individual by the name of Steve Elibank clearly has a keen interest in this, sending off Freedom of Information requests to NHS organisations requesting information on what material has been purchased, how much it cost, titles, etc. The results can be tracked via What Do They Know?

What do we know so far? (please note the links go to the WDTK site and not the organisation).

1. Tayside NHS Board don't seem to supply anything, so it's bring your own.
2. South London Healthcare NHS Trust do indeed provide purchased material, but have otherwise failed to answer the request in detail.
3. Kings College Hospital NHS Foundation Trust "has not spent any public money on pornographic material." All the material has been provided by "a consultants" (sic) and includes "erotic literature and picture magazines". Titles aren't specified, but the tenacious Mr Elibank has requested further details.
4. Barts and the London NHS Trust have spent £100 in the last 18 months on Playboy and Hustler. I wonder who gets to choose.

Lidocaine brain injections for anxiety...not.

Just under a fortnight ago, the Daily Mail printed an article entitled: "The injection that can cure phobias... unless, of course, you're terrified of needles". In it, the reporter (David Derbyshire, listed as the Environmental Correspondent) suggested that the research, "...could lead to new treatments for phobia." Indeed, the comments section (no longer available on the Daily Mail website) included people who were suggesting that they would sign up for injections to cure their phobias.

The article was reporting a study by Japanese researchers (open access):

Yoshida M, Hirano R. Effects of local anesthesia of the cerebellum on classical fear conditioning in goldfish. Behavioral and Brain Functions. 2010;6(1):20. (Paper here)

The study appeared to be either a replication of a similar study by the same lead author, which involved a number of methods (cooling, ablation) to 'inactivate' the goldfish cerebellum.

Yoshida M, Okamura I, Uematsu K. Involvement of the cerebellum in classical fear conditioning in goldfish. Behavioural Brain Research. 2004;153(1):143-148. (Paper here | Not open access)

In the study, they essentially used an electric shock as the unconditioned stimulus, and light as the conditioned stimulus. In response to the shock, goldfish will naturally exhibit slowing of the heartbeat (bradycardia), and by repeated pairings of the light and the shock, they were able to cause the goldfish to demonstrate bradycardia in response to the light alone. The basic process of classical conditioning is explained at Wikipedia.

Injecting lidocaine into the cerebellum had no effect on the goldfishes response to the first light stimulus nor the electric shock. However, it was found that goldfish with lidocaine in their cerebellums were less able to learn the association between the light and the shock.


So, a superficial glance might suggest that anaesthetising your cerebellum might stop you from getting anxious.

There are some problems with the interpretation of this study demonstrated by the press that picked it up:

1. For many people, a simple phobia might not be so problematic as to warrant injections of local anaesthetic into their cerebellums. Since the cerebellum is essential (in humans) for the coordination and sequencing of complex motor actions, anaesthetising it might result in you being unable to move out of the way of one's feared stimulus. But of course, you will no longer be afraid of it.
2. Classical fear conditioning is not the only learning mechanism involved in the maintenance of phobic responses. In more complex organisims (such as humans), instrumental learning/ operant conditioning also plays a part, and not all phobias have a classical conditioning explanation.
3. There are already effective treatments for most anxiety disorders, and simple phobias. Graded exposure has been around for decades, but due to the emphasis of mental health services on 'severe' mental disorders, many of these simple behavioural treatments have been left out of many people's therapeutic armamentarium.
4. Such a 'treatment' would only prevent the acquisition of a specific association, and there is nothing to suggest that you can wipe out a fear of spiders with an injection that would, of course, be temporary.

I would be surprised if we were seeing lidocaine injections into the brain being available on the NHS at anytime in the near future.