How key insights into mental health during lockdown would be missed if we didn’t study individuals

By Dr Felix Naughton, Senior Lecturer in Health Psychology

Before Covid-19 hit, Julie* was “physically and mentally tip top”, as she’d recently lost weight and been busy with house renovations. But the impact of lockdown dramatically cut her off from her social life and her ability to be physically active, while her diet was reduced to “drinking wine and eating crisps”. As a result, and perhaps not surprisingly, in her words she “spiralled into depression”.

However, for retiree Geoff* lockdown was a happy experience. He and his wife spent every day in the garden, taking advantage of the sunny weather at the time.

He started riding on his mountain bike, took up Pilates and, once allowed to, socialised at a safe distance in the garden with friends. Geoff felt very fortunate with where he was in life when the pandemic hit, reflecting that had he “been in a tower block without even a balcony” it would have been a different story.

Looking beneath lockdown wellbeing research

Many studies worldwide have investigated the impact of pandemic-based lockdowns and social distancing measures on health behaviours and mental wellbeing. These studies have found that, on average, health behaviours and wellbeing worsened while such measures were in place.

In other words, lockdowns are bad for healthy lifestyles (although good for lowering our risk of contracting infectious disease). This is unsurprising given that most people’s activities were literally restrained and most, if not all, of us had to put elements of our lives on hold. But underneath these average impacts, are much more interesting, sometimes concerning, findings about who in society had more Geoff-like experiences and who had more Julie-like struggles and why.

In early April 2020, a team of us at the University of East Anglia (UEA) rapidly launched the C-19 Health Behaviour and Wellbeing Daily Tracker study. This study aimed to better understand how pandemic measures in the UK might impact on people’s health behaviours and wellbeing.

We recruited a cohort of more than 1,000 people who completed daily surveys for 90 days, from early April to early July. We then interviewed them and subsequently followed them up six and 12 months after the study started.

Our study found that on average participants reduced their fruit and vegetable consumption by one portion per day compared to pre-pandemic levels, reduced their moderate to vigorous physical activity by 20% (although strength exercises increased by 15%) and drank alcohol on more days.

These sorts of changes might not sound particularly dramatic but across a whole population, even small changes can result in substantial increases in population risk for disease and ill health.

For example, it’s estimated that if the decrease in one portion of fruit and vegetables was sustained (a distinct possibility as new dietary behaviours become habitual), it could increase the population risk in premature death and cardiovascular disease by 5%. Rapid population shifts in disease risk like this are almost unheard of in the modern age.

The hazards of health study statistics

But looking only at average changes can mask individual differences in behaviour change, and consequently individual differences in risk. Some people became healthier during lockdown. For example, more than a quarter (28%) of our participants increased their fruit intake. We also found that while nearly half (48%) of participants reported increasing their high sugar snack consumption, a similar number (44%) reported reducing it. This translated into no change on average, but demonstrates how the average can cover up divergent trends.

When looking at characteristics associated with behaviour change during lockdown, we start identifying the winners and losers and get a sense of how it might affect people differently.

We found that younger people overall fared worse. They had a bigger reduction in their diet quality during lockdown compared to older people across all our dietary measures and a bigger drop in their moderate to vigorous physical activity levels.

Younger people were also more likely to relapse back to smoking if they attempted to quit during lockdown. One behaviour bucked this age-related trend – older participants were more likely to report increases in drinking alcohol compared to younger participants.

We also found that the higher a participant’s body mass index, the worse their dietary and physical activity behaviour change was during lockdown.

People from more deprived areas also had greater reductions in their physical activity and greater increases in their smoking compared to those from less deprived areas. Finally, women had worsening lockdown dietary behaviours and increased drinking frequency relative to men, who in turn drank more per drinking episode than women.

These findings indicate that lockdown hit some of the already disadvantaged groups in society the hardest overall. However, when drawing conclusions from associations using average scores, even among subgroups of people, we miss the experiences of individuals.

Some people who have a high body mass index or are young may have experienced big improvements in their diet during lockdown, contrary to the average changes in these groups. Furthermore, findings based on averages tell us relatively little about why people’s health behaviours or wellbeing may have changed and what we might need to do to improve them.

One of the reasons we collected daily surveys in our study was to track individual behaviour and wellbeing changes over time and identify which factors contributed to any changes for each individual.

For example, an analysis led by UEA Masters student Noor Dhakal examined factors associated with changes in people’s day-to-day happiness during the first lockdown.

Looking at just 10 randomly selected participants (making up almost 900 surveys between them), researchers found two almost universal factors which were statistically associated with wellbeing and several other factors which were only associated for a few people.

The two largely consistent factors across people were higher stress on a given day and poorer sleep quality the preceding night. These were associated with lower happiness, even when accounting for each other.

For several participants, the more physical activity they did on a given day, the higher their happiness, but for others there was no association. And for two participants only, the more fruit they ate each day corresponded with higher happiness ratings on that same day.

The advantages of studying individuals

These types of ‘within-person’ analyses can generate evidence for which factors may be important for most people when it comes to day-to-day wellbeing, such as stress and sleep quality. And also, which factors may be important only for a subset of individuals, such as diet and physical activity.

Also known as ‘single-case’ or ‘N-of-1’ analyses, this study design can directly inform optimal ways of promoting wellbeing and behaviour change during any future lockdowns or similar restrictions for the current or future pandemics, as well as in general. It would be impossible to identify these kinds of relationships if we used average data derived from groups of individuals.

And, potentially more troubling, is that relying on associations derived from averaged rather than individual data can identify relationships that do not actually hold true for many or even any individuals. This is due to a phenomenon known as Simpson’s Paradox.

When it comes to wellbeing, Geoff and Julie’s time trends during lockdown could not have been more different.

Looking at the graphs, you can see that Geoff had very high happiness scores throughout the 90-day measurement period, which rarely deviated away from 9 out of 10.


Julie’s happiness scores, however, varied considerably, reaching a high of 8 in early lockdown but steadily worsening to hit zero by the end of June. You can also see how their perceived stress levels closely corresponded with their happiness.


If we didn’t investigate Geoff and Julie as individuals, then their greatly contrasting experiences would get lost in the average. And it may be at the extremes of experience where we can learn the most about which factors influence behaviour and wellbeing.

* Geoff and Julie are pseudonyms for two participants of the C-19 Health Behaviour and Wellbeing Daily Tracker study. To listen to Geoff and Julie and several others talking about their experiences see the UEA’s Lockdown Voices project.

Felix is Senior Lecturer in Health Psychology in the School of Health Sciences at UEA, and Behaviour Change Consultant at Thrive. He has a primary research interest in investigating how technology, particularly mobile phones, can support behaviour change.

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