Bridging life satisfaction data and neurobiological measures would elucidate human well-being

In 2011, the United Nations’ (UN's) General Assembly unanimously approved a resolution that, for the first time, put happiness on the global agenda. The resolution recognized the pursuit of happiness as a human universal right and urged that a country’s prosperity should not be measured only in economic terms, but also in terms of the contentment and well-being of its people. Consequently, there is a growing interest in systematic investigation of happiness.

For the eighth straight year, the UN Happiness Report recently ranked Finland, whose capital, Helsinki, is shown here, as the world’s happiest country based on self-reported survey data. Could adding neurobiological data offer a more complete picture? Image credit: Shutterstock/Ekaterina Pokrovsky.

Since 2012, the UN has been publishing annual reports ranking the countries of the world in terms of happiness. The UN’s World Happiness Report is based primarily on a three-year rolling average of responses to a single question on the Gallup World Poll: Respondents are instructed to imagine a ladder spanning from 0 to 10, with 0 representing their worst possible life and 10 their best. They are then asked to rate their current life on what has been termed the Cantril Ladder (1). Each year, Gallup surveys fresh cohorts of respondents ages 15 years and older in over 150 countries (2). Finland and other Nordic countries have consistently been at the top of the “happiness” rankings (2, 4). The latest report, released in March, finds that within-country gaps in life satisfaction are increasing, even as worldwide rankings remain constant (4).

Several justifications have been offered for relying so heavily on the Gallup questionnaires. Their large sample sizes de-emphasize individual differences, exposing national trends. Crucially, results strongly correlate with key socioeconomic indicators. The UN’s inaugural report noted that nearly all of the interregional differences can be explained by per capita income, healthy life expectancy, having friends to count on in times of need, having freedom to make life choices, and the absence of corruption (2). Later reports arrive at similar conclusions: For instance, the 2019 report (the last one before the pandemic) found that quality-of-life ratings in the top 10 countries were twice as high as those in the bottom 10, with differences in income and social support as the largest contributing factors (3).

While we see value in these surveys and rankings, we find that there exists a major gap in our understanding of happiness across world populations. As a universal experience, happiness is both a subjective state of well-being and an objective, measurable neurobiological phenomenon. This multifaceted nature of happiness prompts an exploration from various perspectives, including psychological, sociological, and biological. Our understanding of happiness would be enriched by complementing self-reported trends with salient neurobiological measures.

While we see value in these surveys and rankings, we find that there exists a major gap in our understanding of happiness across world populations.

Happiness Biology

As a neurobiological phenomenon, the feeling of happiness is mediated by the release of neurotransmitters and hormones known to promote positive feelings and the subjective experience of happiness. Among these so-called “happy hormones,” dopamine, serotonin, oxytocin, and endorphins play pivotal roles in how we experience joy, contentment, and connection. The release of these chemicals leads to a cascade of reactions that influence mood, behavior, and emotional well-being. Researchers still don’t adequately understand the extent to which these biological features differ among populations and the degree to which their levels are implicated in subjective appraisals of contentment.

The “happy hormones” impact human mood and behavior in different ways. Dopamine is often referred to as the “reward” chemical, as it plays a central role in motivation, pleasure, and reward processing. Dopamine dysregulation has been linked to disorders such as depression and addiction (5). Serotonin is associated with feelings of well-being, contentment, and stability and is involved in regulating mood, appetite, and sleep. Many antidepressant medications, particularly selective serotonin reuptake inhibitors, work by increasing serotonin levels in the brain (6). Oxytocin is known as the “love hormone” or “bonding hormone,” as it is crucial in forming emotional bonds. Oxytocin release is triggered by physical touch, such as hugging or holding hands, and by positive social experiences (7). Finally, endorphins are the body’s natural painkillers. They are released in response to physical exercise, stress, or pain and help to reduce discomfort while promoting a sense of euphoria (8).

Genetics affect the levels of these neurotransmitters. As a result, the subjective feeling of well-being is influenced by heritable biological factors. Tellegen et al. (9) found that the feeling of well-being of identical twins raised apart was more similar than that of fraternal twins raised together. Later reviews of twin studies—with sample sizes in the tens of thousands—reinforced those findings, suggesting that heritability accounted for 30–40% of the variation in subjective measures of well-being (10). Indicative of that correlation, several studies point to an association between the 5-HTTLPR gene, which codes for serotonin transmission, and life satisfaction. The gene occurs in long (L) and short (S) alleles, inherited in pairs from one’s parents. Subjects with a pair of “L” alleles were found to be significantly more satisfied with life than those with two “S” alleles (11).

Researchers have found that genetic variations are unevenly distributed worldwide. For instance, Chen et al. (12) reported that longer alleles for the DRD4 dopamine receptor gene were more prevalent in migratory populations than sedentary ones. Murdoch et al. (13) identified “significant variation worldwide” in the serotonin transporter gene SLC6A4. Butovskaya et al. (14) found geographic differences in oxytocin gene expression. Expression of the MAO-A gene, which predicts happiness in both women and men (15), varies in different regions. Reviewing the data, Way and Lieberman (16) observed that “across multiple genes…it appears that there is a relationship between allele frequency and cultural orientation” (p. 206). They suggest that societies that prioritize individualism may have different genetic profiles than those than are collectivistic, though this intriguing correlation leaves open the direction of causation: Are genetics leading to more individualism, or are “go it alone” cultures selecting for certain alleles?

There are other reasons why neurotransmitter levels might differ across populations, including diet. For instance, drinking an excessive amount of alcohol impairs serotonin synthesis (17). The amino acid tyrosine is a dopamine precursor: Tyrosine supplements have been used to treat stress (18). Low levels of metals such as zinc, magnesium, selenium, and iron have been associated with major depressive disorder (19).

Environmental factors also play a role: For instance, serotonin levels increase with longer daylight hours, potentially contributing to Seasonal Mood Disorder (20). Finally, there may be distinctive cultural factors. Subjective well-being is often described as following a U-shaped curve, declining in middle age and then rising in old age, but that research has largely been conducted in Western countries. Meanwhile, Gurven et al. (21) studied subjective ratings from 23 low-income countries and found well-being more often trending lower in later life. The authors conclude that the oft-cited U-shaped happiness trajectory does not reflect a fundamental characteristic of people worldwide.

The Neurobiology of Populations

These considerations lead us to wonder whether systematic differences between the baseline neurobiological characteristics—linked to the subjective experience of well-being—exist at the population level. Comparing the baseline levels of the “happy hormones” (dopamine, serotonin, oxytocin, and endorphins) in samples drawn from different populations worldwide is a reasonable first step in addressing this question. By investigating the extent to which population differences exist, researchers could address a wide range of issues. For example, we could assess the degree to which self-reported assessments align with biological measures in different cultural contexts. We could also better understand any regional peculiarities and differences in mental health, and even the relationship between the socioeconomic and neurobiological variables in society. Knowing whether neurobiological characteristics exist at the population level is also essential for understanding of the world ranking of happiness. If no systematic differences exist in the average baseline levels of “happy neurotransmitters” across different countries, then the vast differences in happiness rankings can be fully interpreted in socioeconomic–cultural terms. If, on the other hand, significant differences in population baseline neurotransmitter levels exist, then this opens the door to a whole plethora of essential questions, which can be explored through further research. For example:

• (a)Is there a causal relationship between happiness rankings and population neurotransmitter levels across societies, and, if so, what is the direction of this causation?
• (b)What are the ramifications of the population differences in the baseline “happy neurotransmitter” levels for the mental health issues in different societies?
• (c)Are the “happy neurotransmitter” levels immutable for a given population, or are they modifiable by cultural/socioeconomic factors? To what extent do gene–environment interactions play a role?

While it may be appealing to depend upon rankings of subjective experience, there are reasons to be skeptical. There could be a lack of self-awareness among survey participants, as well as social pressures to conform. In a recent study, Andreoni et al. (22) asked participants to subjectively rate their well-being under various circumstances, along with how they would report those feelings. Surprisingly, they found that subjects frequently admitted to varying degrees of misreporting, with personal matters like romantic breakups distorted more markedly than work-related ones. Another concern is that reducing self-reported happiness to a single question, as is the case with the UN reports, may be too blunt of a tool. A recent study by Nilsson et al. (23) found that, while Scandinavian countries consistently outpace other countries in the World Happiness Report, their rankings declined when other measures of positive affect—such as enjoyment and low stress—were taken into account. Meanwhile, Kaufman et al. (24) found that respondents in the Kilimanjaro region of Tanzania—a country typically at the low end of the rankings—struggled with expressing their life experiences in terms of the linear Cantril Ladder scale.

Policymakers generally consider income as the greatest predictor of life satisfaction and economic development as the greatest driver of personal happiness. However, Kahneman and Deaton (25) are among those who have found that while less money is associated with emotional pain, life evaluation and emotional well-being can become decoupled at higher income levels: More money does not necessarily buy more happiness. One reason: People tend to compare their wealth to others, rather than viewing it on an absolute scale.

While the importance of economic self-sufficiency should not be underestimated, a more holistic approach to the assessment of happiness would provide a window into how neurochemical characteristics at the population level may influence group cognitive and affective characteristics and how factors other than income—including genetics, diet, environment, and culture—may inform a population’s life satisfaction. A database charting the neurobiology of populations across the world—for instance, group averages of neurotransmitters associated with well-being—would add unique value to the UN World Happiness Report, adding a neurobiological dimension to existing metrics.

Happiness is not just a state of mind; it is a state of the body, including the brain. Neurochemistry offers a complementary tool to assess global well-being, with implications for public health policies, economic planning, and cross-cultural dialogue. Existing evidence suggests that there may be measurable differences worldwide, arising from both heritable and environmental factors. Given that happiness is a vital part of the human condition, we should find better ways to track and understand these differences.