Current treatments for depression mainly focus on psychopharmacology. Medications improve the mood and are effective in alleviating some adverse changes in emotional reactivity, but their long-term use can lead to potentially harmful side effects.

Previous research has shown that an alternative - a cheap one, accessible to everyone and free of undesirable effects - may be physical exercise.

'We know that exercise has a positive effect on health. We often talk about in the context of improving sleep, lowering blood pressure, lowering cholesterol, etc. But recently, it has been increasingly noticed that activity also improves the mood and cognitive functioning, which means that it has an impact on our mental state. It has a positive effect on both healthy people and people suffering from depression. However, much less attention has been paid so far to its impact on emotional reactivity. And taking into account the general beneficial effect of exercises on mood, we can expect that they will also have a positive impact on this variable,’ Dr. Tomasz Ligęza from the Institute of Psychology of the Jagiellonian University tells PAP.

The way we respond to emotions is very important for our mental functioning. For example, people who have higher emotional reactivity quickly react to even small stimuli with a high level of anxiety, while people with lower reactivity do not notice those stimuli at all.

In healthy people, reactivity is 'constant', which means that they respond with similar intensity to both negative and positive stimuli. This tendency is disturbed in people with depression: they process negative stimuli more strongly and positive ones have much less effect.

'For example, when we show people with depression photos of sad faces, images of suffering, etc., their emotional response will be much greater than when we show them something nice: beautiful cats, laughing children,’ says Dr. Ligęza.

'Our previous studies involving healthy people have suggested that emotional reactivity after exercise changes for the better, i.e. positive stimuli are processed more strongly and negative ones less strongly. You could say that the brain begins to pick up what is pleasant and filter out the negative. We all notice that we feel better mentally after exercising,’ he adds.

Dr. Ligęza and his colleagues decided to check whether even a single exercise session can change the cognitive and, above all, emotional functioning of a person. 'It has previously been proven that participation in a long-term training program for several months, several times a week, brings undeniable benefits. I wanted to check what the change looks like after a single, half-hour session of aerobic exercise, such as cycling,’ he says. 

The study, the results of which were published in the journal Psychophysiology (https://doi.org/10.1111/psyp.14137), included 24 people with depression and 24 healthy people, constituting the control group. Their mood and emotional reactivity were assessed before and after two experimental protocols. In the first one, participants performed moderate-intensity exercises for 36 minutes, and in the second one, they remained at rest for the same time.

'When assessing the functioning of the participants, we focused on their mood and emotional reactivity. We measured the variables we were interested in, compared the state before and after, and also whether the state after differed on the day when people were training and when they were simply resting,’ says Dr. Ligęza.

While participants self-reported their mood, their emotional reactivity was measured using EEG. During the measurement, the researchers showed them standardised photos with different stimulation rates. 'For example, a photo of a smiling couple is low on the stimulation scale, while images depicting erotic scenes or great sports emotions are high. It's the same with negative emotions: a photo of a sad face has a low stimulation level, a photo of a serious car accident has a high level.’

It turned out that in both groups - healthy people and those suffering from depression - the mood significantly improved after exercise. In patients with depression, this effect was even stronger. 'In their case, the increase was really very large,’ says Ligeza. 

However, in the case of reactivity, the researchers' hypotheses were only partially confirmed. 'We have confirmed that in healthy people, exercise improves the response to positive stimuli and reduces the response to negative stimuli. However, in people with depression, contrary to our expectations, this effect was small. This is probably due to the fact that they generally have lower emotional reactivity,’ Ligęza adds.

The scientist explains that psychologists call this state emotional blunting. 'This is a known effect that results in part from the fact that in depression the level of energy expenditure generally decreases, which causes the body to be in a state of slight +hibernation+,’ he continues. 

'Therefore, a single exercise session cannot reverse the physiological changes in the brain that are responsible for lower emotional reactivity. However, based on other studies, we can assume that a longer training program (e.g. several sessions) would also cause significant changes in this area.

'What is important in our study is that the mood of the participants with depression improved so much. Although there were no obvious changes at the brain level in people with depression after a single exercise session, the changes at the mood level were very significant. In turn, healthy people saw great benefits in both of these areas,’ he says. 

Additional analyses conducted on both groups revealed that exercise-induced changes in emotional reactivity depended on the severity of depression symptoms: the effectiveness of activity in improving this parameter decreased with the severity of depression symptoms.

PAP - Science in Poland, Katarzyna Czechowicz

kap/ zan/

tr. RL