Lonely individuals show greater mood instability, especially with positive emotions, study finds

New research published in Cognition and Emotion suggests that people who feel lonelier tend to experience more emotional ups and downs—especially with positive emotions—throughout their daily lives. These fluctuations appear to persist even when accounting for depression, average mood levels, and objective measures of social isolation.

Loneliness is not simply the absence of people. It refers to the emotional experience of perceiving a gap between the social connections one has and the connections one desires. It is different from social isolation, which involves an objective lack of social contact or interaction. A person can be surrounded by others yet still feel lonely if those relationships lack depth, reciprocity, or emotional closeness.

By contrast, someone who lives alone or has a small social circle might not feel lonely at all if they are satisfied with their relationships. In short, loneliness is about subjective dissatisfaction, while social isolation refers to measurable contact with others.

Previous research has already shown that loneliness is linked to more frequent negative emotions and fewer positive ones. But emotional experience is not just about how someone feels on average. Another important aspect is emotional instability—how much a person’s emotions fluctuate from moment to moment or day to day. Emotional instability has been associated with worse psychological and physical health outcomes, including chronic illness, inflammation, and even early death. But until now, little was known about whether loneliness is tied to these moment-to-moment shifts in emotion.

“I’ve long been interested in how loneliness impacts people’s behavior and emotions in everyday life, including how those emotions fluctuate from day to day,” said study author Jee eun Kang, a postdoctoral researcher at the Center for Healthy Aging at Penn State.

“Most research on loneliness and emotion looks at whether lonely people feel more negative or less positive emotions on average, but that only tells part of the story. I wanted to know—are lonely people’s emotions also less stable? Do they swing more from one day to the next? Emotional instability can be just as important for mental and physical health as average mood, so it felt like an important gap to fill.”

The researchers recruited 252 adults aged 25 to 65 from Co-Op City in the Bronx, New York. The sample was racially and economically diverse, with most participants identifying as Black, non-Hispanic, and female. After completing baseline questionnaires in the lab—including a measure of loneliness—participants were trained to use smartphones provided by the study.

Over the next two weeks, participants received five random alerts per day prompting them to report their current emotional state. Each time, they rated how positive (e.g., happy, joyful) and negative (e.g., angry, frustrated) they felt using a scale from 0 to 100. To measure emotional instability, researchers calculated how much these emotional scores changed from one day to the next, using a metric called mean squared successive difference.

Importantly, participants were only included in the analysis if they provided at least three days of usable emotion reports. This allowed for meaningful estimates of emotional fluctuations.

The results indicated that loneliness was significantly associated with greater day-to-day emotional instability—both in terms of positive and negative emotions. People who scored higher on loneliness tended to have more dramatic emotional swings from one day to the next.

“Loneliness isn’t just about feeling more negative or less positive—it’s also about greater emotional volatility, especially for positive emotions,” Kang told PsyPost. “In our study, lonely individuals showed more day-to-day instability in positive emotions, even after accounting for depression and other factors. This suggests that loneliness may make positive moods harder to sustain, which could have downstream effects on well-being and health.”

When they adjusted for demographic factors and objective social isolation, loneliness still predicted more variability in both positive and negative emotions. When average emotional levels were also accounted for, loneliness remained a significant predictor of both types of instability. However, once depressive symptoms were factored in, the link between loneliness and instability in negative emotions was no longer statistically significant. In contrast, the connection between loneliness and instability in positive emotions remained robust.

This pattern suggests that emotional volatility in negative feelings may be more closely tied to depression than to loneliness alone. But fluctuations in positive emotions appear to be more uniquely related to loneliness, beyond what can be explained by depression or other emotional traits.

“I was surprised by how consistent the link was between loneliness and positive emotion instability, and how it held up even after adjusting for depressive symptoms,” Kang said. “I had expected the link with negative emotion instability to be stronger, but that relationship disappeared once we accounted for depression. This tells me there’s something unique about how loneliness disrupts the stability of positive feelings.”

These results provide evidence that loneliness is not only associated with how people typically feel, but also with how much their emotions fluctuate—particularly in response to positive experiences. The authors propose that lonely individuals may struggle to sustain positive feelings over time. A pleasant event might lift their mood temporarily, but the benefits could fade more quickly compared to those who feel more socially connected.

This might explain why emotional instability was especially pronounced in positive emotions for lonely individuals. Even uplifting moments may not provide lasting comfort, possibly due to differences in how lonely people process or regulate emotions.

“From a methods perspective, using ecological momentary assessment was key,” Kang explained. “By tracking people’s emotions multiple times a day over two weeks, we were able to capture patterns that can’t be seen in one-time surveys. From a practical standpoint, these findings suggest that interventions for loneliness might need to focus not only on increasing positive experiences, but also on helping people sustain those good feelings and maintain more stable, positive emotional states.”

While the study provides new insight into how loneliness affects everyday emotions, it also has some limitations. Loneliness was measured only once at the start of the study. Yet loneliness can fluctuate over time depending on life circumstances. Future studies might use repeated assessments of loneliness to better track how changes in perceived social disconnection relate to emotional dynamics.

The research design also doesn’t allow for clear conclusions about causality. It remains unclear whether loneliness causes emotional instability, or whether people who tend to be more emotionally volatile are more likely to feel lonely over time. Longitudinal or experimental studies could help clarify this question.

Looking forward, “I’d like to explore why loneliness is so strongly tied to instability in positive emotions,” Kang said. “One possibility is that lonelier individuals may have trouble sustaining the benefits of good experiences—that their mood boost from a positive event might fade more quickly. As a next step, we’ve examined whether loneliness is linked to different emotional responses to positive events, both in the moment and hours later.

“That study is currently under review, but it will help clarify whether these fleeting benefits of uplifts contribute to the greater volatility in positive emotions we observed here. Ultimately, I hope this line of work will point to intervention strategies that not only increase positive experiences, but also help people hold onto those good feelings for longer.”

The study, “Higher loneliness is associated with greater positive and negative emotion instability in everyday life,” was authored by Jee eun Kang, Dusti R. Jones, Joshua M. Smyth, and Martin J. Sliwinski.