"Stress can be transmitted through TV screen," The Daily Telegraph's website reports. The site's report uses an image from hit US TV series "Breaking Bad" to imply that box-set binges may not be good for your stress levels. But the study in question involved real people, not fictional characters.
Researchers measured people's stress response to watching either a loved one, or a stranger of the opposite sex, in a stressful situation – specifically being asked to do a mock job interview and mental arithmetic.
Around one in four "observers" (26%) experienced heightened stress levels – measured using salivary cortisol levels – when watching the "targets". As may be expected, the observer was more likely to be stressed if the person they were watching was their partner (40% of observers becoming stressed) rather than a stranger (10%).
There are important limitations to consider – not least the highly artificial study design. The study also does not provide any evidence about the development of stress-related mental health conditions.
It is possible to put a positive spin on the study's findings, however. It may show that some humans are innately empathic and it often upsets us when we see loved ones – and in some cases, strangers – in stressful circumstances.
Where did the story come from?
The study was carried out by researchers from the Max Planck Institute for Human Cognitive and Brain Sciences and Dresden University of Technology in Germany. No external funding was obtained.
It was published in the medical journal Psychoneuroendocrinology – it has been accepted for publication and is currently available as an unedited manuscript. This is not the final publication of the study and may include some errors.
The media has linked this study to TV viewing because of the researchers' observations of participants watching someone through a video link, rather than through a one-way mirror.
It is entirely plausible that we may display similar stress responses when watching TV or film involving characters that we have come to invest in emotionally.
However, this study has not directly measured a person's response to watching an action or emotional film or drama, for example. The media's spin on the research is therefore somewhat misleading.
What kind of research was this?
This was an experimental study that aimed to see whether we give a stress response from observing another individual going through a stressful situation.
The researchers also wanted to see if any potential response was influenced by our relationship to the person involved (for example, whether it's a stranger or loved one) and whether any effect differs between men and women.
The researchers discuss how it has often been questioned whether stress in our environment has the ability to "contaminate" us. The response being examined by this study was so-called "empathic stress" – defined as a full-blown physiological stress response arising solely from observing a target undergo a stressful situation.
What did the research involve?
The study involved measuring the stress response of individuals observing either a loved one or a stranger of the opposite sex in a stressful situation.
It was carried out at two research centres in Germany. One centre recruited 51 opposite-sex couples and 40 male-female paired strangers; the second centre recruited 60 opposite-sex couples and 60 strangers. Participants were aged 18 to 35 years, and the couples had to have been in a relationship for at least six months.
They did not include people with any condition that could have any effect on their stress hormone levels. This included people with chronic illness, women taking hormonal contraceptives, smokers or recreational drug users, or those reporting chronic illness.
The experiments were performed in one 130-minute afternoon session. Participants were informed whether they were acting as the "observer" or the "target" in the study. In the first centre, one observer watched one target (either partner or stranger) through a one-way mirror. Researchers labelled this as the "real-life modality".
In the second centre, both a partner and a stranger observed one target at the same time in separate rooms via live video transmission. This was labelled as the "virtual observation modality".
The stressful situation involved was the Trier Social Stress Test (TSST), a laboratory method said to give the most reliable stress responses. It involves a five-minute anticipation phase, followed by the person having to give a five-minute mock job talk and carry out difficult mental arithmetic for five minutes, all the while being probed and evaluated by two behavioural analysts.
Stress was measured in both the observers and targets by measuring salivary stress hormone levels (cortisol and alpha-amylase) before TSST, and then at 10-minute intervals in the hour after. Heart rate was also measured before and during TSST.
Observers also completed a test called the 16-item German version of Davis' Interpersonal Reactivity Index (IRI), which is said to assess four aspects of empathy: fantasy, empathic concern, perspective taking and personal distress.
What were the basic results?
During the TSST test, the majority of targets (144 out of 151 targets, 95%) displayed a physiologically significant increase in their cortisol levels, defined as an increase of at least 1.5nmol/l over baseline.
Overall, a quarter of observers (54 out of 211 observers, 26%) similarly displayed physiologically significant cortisol increases.
Observers were more likely to display these significant cortisol increases when they were observing their partner (44 out of 111, 40%) rather than a stranger (10 out of 100, 10%).
They were also more likely to be stressed observing via the "real-life modality" (15 out of 50, 30%) rather than the "virtual modality" (39 out of 161, 24%).
Women observers were slightly more likely to display these cortisol stress responses (40 out of 149, 27%) than male observers (14 out of 62, 23%).
How did the researchers interpret the results?
The researchers conclude that the occurrence of empathic stress, in some cases even when observing total strangers and when only witnessing another's distress via video screen, may have important implications for the development of stress-related diseases.
This is an interesting experimental study which suggests that observing the stress of others leads to an increase in our own stress levels. As expected, personal stress is more likely when the other person involved in the stressful situation is a loved one rather than a stranger.
However, there are several considerations to bear in mind when interpreting these findings:
- The study only examined opposite sex pairs – that is, opposite-sex couples in a relationship and observing a stranger of the opposite sex. We don't know what the stress response would be for a person observing a stranger of the same sex, or a same-sex partner, in a stressful situation. We also don't know what the stress response would be for a person observing a person (either the same or opposite sex) in a stressful situation who they had a different relationship with (such as a friend or family member, rather than partner).
- It is not clear the extent to which the participants understood the purpose of the study. It is reported that they were informed whether they were observer or target, and that the targets knew they were being observed during the experiments, though they did not know by whom. The observers also signed a document beforehand so they understood that they would not be subjected to the stress test themselves, which was to try to control for them possibly being stressed through that expectation. However, overall, it is possible that the whole experimental scenario of knowing that they were taking part in a study and that they were being observed may have heightened stress levels and made them less representative of the real-life situation.
- Also related to this, the stressful situation they were observing was a person being asked to carry out a job talk and do mental arithmetic while being questioned by behavioural analysts. While this may be a verified way of inducing psychological stress in the laboratory setting, for the observer witnessing this is not likely to be comparable to watching their partner or a loved one in more distressing circumstances, such as being in pain, fear, or other heightened emotional states. Therefore, this experimental scenario may not be comparable to the level of stress that we may experience by observing a person under different real-life stress situations.
- Similarly, the researchers observed a stronger link with what they reported to be the "real-life" representation of the stressor, such as observing through a one-way mirror rather than over the virtual representation via video transmission. It does seem plausible that in real-life a person may be more influenced by witnessing something in person rather than more remotely. However, again, the fact that they were still observing only this specific TSST test, and in an artificial laboratory setting, does not make this necessarily representative of "real" life just because they were directly witnessing it.
- The study also involves only a relatively small sample of healthy young participants recruited to two academic centres in Germany. The same results may not be obtained in larger or different population samples.
- The media has linked this to TV viewing because of the researchers' observations of the "virtual" link. Though it is entirely plausible that we may display similar stress responses when watching TV or film, this study has not directly measured a person's response to watching an action or emotional film or drama, for example.
Lastly, the researchers suggest that their findings could have "important implications for the development of stress-related diseases". But the development of stress-related mental health conditions was not assessed by this study, so this assumption cannot be made.
You could choose to spend your life avoiding all television news and watching only heartwarming comedies. But it could be the case that this would make you less, not more, able to cope with real-life stressful events. Trying to create a highly unrealistic view of the world rather than confronting reality is potentially unhelpful.