Published by the New York Times June 6, 2018
By Gretchen Reynolds
Benefits essentially were the same whether people went to the gym twice a week or five times a week.
Lifting weights might also lift moods, according to an important new review of dozens of studies about strength training and depression. It finds that resistance exercise often substantially reduces people’s gloom, no matter how melancholy they feel at first, or how often — or seldom — they actually get to the gym and lift.
There already is considerable evidence that exercise, in general, can help to both stave off and treat depression. A large-scale 2016 review that involved more than a million people, for instance, concluded that being physically fit substantially reduces the risk that someone will develop clinical depression. Other studies and reviews have found that exercise also can reduce symptoms of depression in people who have been given diagnoses of the condition.
But most of these past studies and reviews have focused on aerobic exercise, such as walking or jogging.
Far less has been known about the possible benefits, if any, of strength training for mental health. One 2017 analysis of past research had found that strength training can help people feel less anxious and nervous.
But anxiety is not depression.
So for the new study, which was published in May in JAMA Psychiatry, the same researchers who earlier had examined anxiety and resistance exercise now turned their attention to depression.
They wanted to see whether the available research could tell us if lifting weights meaningfully affects the onset and severity of depression. They also sought to determine if the amount of the exercise and the age, health or gender of the exercisers would matter.
The researchers began by gathering all of the best past studies related to resistance exercise and depression. They were interested only in randomized experiments with a control group, meaning that some people had been assigned to start exercising while others had not. These experiments are the gold standard for testing the effects of exercise and other interventions.
The experiments also had to include testing for depression before and after the training.
The researchers ultimately found 33 experiments of weight training and depression that met their criteria. The studies involved almost 2,000 men and women of various ages, some of whom had been diagnosed with depression, while others had not.
The researchers aggregated the results from all of these studies and then began digging through the data.
What they found was that resistance training consistently reduced the symptoms of depression, whether someone was formally depressed at the start of the study or not. In other words, if people began the study with depression, they usually felt better after taking up weight training. And if they started out with normal mental health, they ended the experiment with less chance of having become morose and sad than people who did not train.
Perhaps most interesting, the amount of weight training did not seem to matter. The benefits essentially were the same, whether people went to the gym twice a week or five times a week and whether they were completing lots of repetitions of each exercise or only a few.
The mental health impacts were similar, too, for men and women and for younger lifters (often college students) and people who were middle-aged or elderly.
And people did not need to pack on mass or might to reduce their depression. More strength after the experiment did not correlate with less depression, the researchers found.
All that mattered was showing up and completing the workouts.
Only a few of the studies had also included a separate group who tried aerobic exercise, making it difficult to compare the effects of that kind of workout with those of lifting weights.
But while the number of people involved was small, the combined results suggest that weight training and aerobic exercise have similar impacts on depression, the authors of the new review conclude.
Both types of exercise reduced symptoms, and to about the same extent.
This kind of review cannot tell us, though, how strength training might be influencing mental health.
The exercise probably has both physiological and psychological consequences, says Brett Gordon, a graduate student at the University of Limerick in Ireland, who led the new review. The weight training could be changing aspects of the brain, including the levels of various neurochemicals that influence moods, he says.
“Expectancy could also be at work,” he says. People expect the workouts to make them feel more cheerful, and they do. (It’s impossible to blind people about whether they are lifting weights or not, he points out. So some of the psychological benefits might be the result of a biological placebo effect, which nonetheless produces real benefits.)
The review’s results do not indicate that resistance training is better for combating depression than other kinds of exercise, Mr. Gordon says. Nor do the results suggest that exercise can, or should, replace traditional therapies, including medication.
But as a whole, he says, the data do suggest that visiting the gym and lifting weights a few times a week might be an effective way to buoy mental health.