You may have seen the reports this week that physical exercise is ineffective as a treatment for depression. Well, I don’t agree. John Campbell, Professor of General Practice and Primary Care at Peninsula College of Medicine and Dentistry at Exeter University, described it as a ‘carefully designed research study’. But was it?
Here’s what happened. Researchers from the Peninsula College, together with those from Bristol University, took 361 patients aged 18 to 69 with mild to severe depression, and divided them into two groups. Half were given the ‘usual care’ and half were given ‘usual care’ and, in addition, advised to take exercise. At the end of one year the two groups were assessed. Those assigned to the ‘exercise group’ were slightly less depressed but the difference was not considered large enough to be statistically valid.
So, if you suffer from depression, can you drop the exercise? Well, of course, exercise has other well-known health benefits, so that wouldn’t be a good idea on physical health grounds anyway. But the two big flaws in this study were, firstly, that it relied upon self-reporting of exercise levels and, secondly, that the ‘exercise group’ only did, on average, twice as much exercise as the others (assuming they didn’t exaggerate).
Now, most people don’t take much exercise. So testing the effects of doing twice as much is far from conclusive. Twice nothing is nothing. All that happened was that the ‘exercise group’ met PE trainers three times face to face and had 10 telephone calls. If I’d been running the trial I’d have had regular organised exercise sessions at, maybe, three different levels.
Now, it doesn’t take a lot of exercise to make a difference but it does have to be vigorous. For example, as I reported in my book How To Be Happier just eight minutes of exercise increases noradrenaline (norepinephrine for US readers) up to ten times, while 12 minutes increases endorphins five times, and 30 minutes almost doubles PEA. All these chemicals are mood boosters. But the research that produced these findings was conducted on people exercising vigorously, which is to say, at around 70 per cent of maximum heart rate. At that level you’d still be able to talk but you’d be puffing.
The researchers took the view that it wasn’t realistic to ask depressed people – possibly middle-aged, overweight people who didn’t normally exercise – to, say, get a bicycle and cover 20 miles a day. Fair enough! But that’s not a comment on the efficacy of exercise. All this study has shown is that ambling along behind a dog does little to combat depression. My advice is to ignore the headlines. Keep exercising. The more the better.