Relatedness is the human need to feel connected to and cared about by other people. It’s one of three basic psychological needs identified in Self-Determination Theory, alongside autonomy (feeling you’re choosing your own behavior) and competence (feeling effective at what you do). The term also has a separate meaning in biology, where it describes the degree of genetic overlap between family members. Both uses come up frequently in psychology, education, and science, so understanding each one matters depending on context.
Relatedness as a Psychological Need
Psychologists Edward Deci and Richard Ryan proposed in their Self-Determination Theory that all humans share three innate psychological needs that drive growth, motivation, and well-being. Relatedness is the social one: it captures the feeling of belonging, of being genuinely connected to others rather than isolated or superficially linked. It’s not just about having people around you. It’s about feeling that those relationships are warm, reciprocal, and meaningful.
This need is considered universal across cultures. When relatedness is satisfied, people tend to be more internally motivated, more energized, and more psychologically healthy. When it’s frustrated, the opposite happens. Researchers sometimes measure relatedness frustration with statements like “I feel that the relationships I have are just superficial,” which captures the hollow quality of unmet social connection even when someone isn’t technically alone.
How Relatedness Affects Motivation and Energy
Relatedness doesn’t just make you feel good socially. It has a measurable effect on how motivated and alive you feel during everyday activities. Research on university students taking online classes during social distancing found that when instructors actively supported students’ sense of connection, students reported greater relatedness satisfaction. That satisfaction, in turn, predicted higher intrinsic motivation and greater vitality, which researchers define as the positive feeling of being alive and energetic.
The chain works like this: someone in a position of influence (a teacher, manager, coach) creates conditions where you feel seen and connected. That feeling of connection satisfies your relatedness need. And satisfying that need fuels your internal desire to engage with what you’re doing, not because you have to, but because you want to. The study confirmed this pathway statistically, showing that relatedness satisfaction acted as a bridge between the support people received and the motivation they felt.
This matters beyond classrooms. The same dynamic plays out in workplaces, sports teams, families, and friendships. When people feel genuinely connected to those around them, they bring more energy and engagement to whatever they’re doing.
What Happens When Relatedness Is Thwarted
The flip side is significant. When people feel disconnected from others, or sense that no one genuinely cares about them, their psychological health deteriorates. Researchers use the term “thwarted belongingness” to describe this state, characterized by feeling disconnected from other people or perceiving a lack of reciprocity in caring relationships.
Thwarted belongingness on its own doesn’t always lead directly to severe outcomes. But when combined with psychological distress, it becomes a meaningful pathway toward serious mental health consequences. One study of college students found a significant indirect effect: adverse childhood experiences contributed to thwarted belongingness, which intensified psychological distress, which in turn was associated with suicidal ideation. Social connectedness, on the other hand, buffered the psychological effects of stressful situations and was linked to lower levels of suicidal thinking.
This underscores that relatedness isn’t a luxury or a personality preference. It functions as a psychological nutrient. Depriving someone of it creates real vulnerability, especially when combined with other stressors.
Relatedness vs. Belongingness
You’ll sometimes see “relatedness” and “belongingness” used interchangeably, but they come from slightly different traditions. Relatedness is the term used within Self-Determination Theory and refers specifically to the innate need for connection that drives motivation and well-being. Belongingness, popularized by psychologist Roy Baumeister, focuses on the broader human drive to form and maintain positive social bonds.
In practice, the two overlap heavily. Both are considered universal and fundamental. Both predict well-being when satisfied and distress when frustrated. The main distinction is theoretical framing: relatedness sits within a motivation framework (it explains why you engage with tasks and people), while belongingness sits within a social-psychological framework (it explains why humans form groups and maintain relationships). For most practical purposes, satisfying one means satisfying the other.
The Physical Side of Social Connection
Relatedness satisfaction isn’t just a mental state. Social isolation and loneliness leave signatures in the body. Research examining blood proteins in large population studies has found that social disconnection is associated with changes in stress-related hormones, inflammatory markers like C-reactive protein, and metabolic indicators including cholesterol and triglycerides. One protein of interest, adrenomedullin, plays a role in organizing the body’s stress response and may influence the release of oxytocin, a hormone central to social bonding.
These aren’t minor associations. The proteomic signatures linked to social isolation were themselves associated with increased risk of disease and mortality. In simple terms, your body responds to chronic loneliness the way it responds to chronic stress, with elevated inflammation, disrupted metabolism, and a heightened state of physiological alert.
Relatedness in Biology: Genetic Overlap
In evolutionary biology, “relatedness” means something entirely different. The coefficient of relatedness quantifies how much genetic material two individuals share because of common ancestry. It answers the question: if you pick a random gene from one person, what’s the probability that a specific relative carries an identical copy of that gene inherited from the same ancestor?
For common family relationships in humans:
- Parent and child: 50% shared genetic material
- Full siblings: 50% on average (though the exact amount varies)
- Half siblings: 25%
- Grandparent and grandchild: 25%
- Uncle/aunt and niece/nephew: 25%
- First cousins: 12.5%
- Identical twins: 100%
This concept matters because it underpins a major idea in evolutionary biology: kin selection. The theory explains why organisms sometimes sacrifice their own interests to help relatives. From a genetic perspective, helping a sibling who shares half your genes can be just as effective for passing on those genes as helping yourself. The biologist J.B.S. Haldane reportedly quipped that he’d lay down his life for two brothers or eight cousins, which is a rough summary of the math involved.
Researchers calculate these coefficients using pedigree analysis, tracking how alleles (gene variants) are passed through family trees. The math gets more complex when founders of a family line are themselves related, but the core idea remains the same: relatedness measures the probability of sharing identical genetic material through common descent.
Why Both Meanings Matter
The psychological and biological definitions of relatedness share an intuitive thread. Humans evolved in small groups of close genetic relatives, and the deep need to feel connected to others likely has roots in that evolutionary history. The biological reality of genetic relatedness helped shape the social instincts that Self-Determination Theory now measures as a psychological need.
Whether you encountered this term in a psychology class, a biology textbook, or a workplace training, the core insight is the same: connection to others is not optional for humans. It’s wired into both our genes and our psychology, shaping everything from how motivated you feel at work to how your body handles stress.