Science is coming to grips with a complex emotion that was once dismissed as sentimental or downright pathological.

It was a way to survive: “We used our memories to temporarily alter our perception of the state we were in. It was not a solution. But the temporary change in perception allowed you to persevere just a bit longer,” a concentration camp survivor told researcher Tim Wildschut. “Nostalgia compensates for uncomfortable states,” he says, a neurological defense mechanism that can heal psychic wounds.

Yet nostalgia hasn’t always been seen so positively. The word was coined in the 1680s as a medical term for the homesickness commonly found among soldiers, an affliction they could literally die from. In 1892, English physician D. H. Tuke understood its seriousness: “Nostalgia always represents a combination of psychological and bodily disturbances, and for this reason it must always be defined as a disease.”

The Pull of the Past

Around the same time, American psychologist L. W. Kline discovered that nostalgia was a reaction to disruption, such as loss of the familiar, the presence of something new or strange, restriction of liberty, and major lifestyle change. Soon, nostalgia switched from a curable physical illness to an incurable condition of the psyche. Whereas physicians had assumed that home was the object of wistfulness, psychologists now understood that past experiences could elicit these intense feelings too.

In Freud’s footsteps, nostalgia became “a variant of depression, … a defense against mourning, or a longing for a past forever lost”, another American psychologist, H. A. Kaplan, wrote in 1987. At the core of this is yearning for original oneness with one’s mother, a symbiotic relationship that can never be replicated.

We all of course depend on memories for a sense of who we are. These can be triggered by many things: a sound, smell, or taste; an object or symbol that represents a moment past. The visceral physicality and emotional impact of these moments of nostalgia are powerful – Proust’s madeleine comes to mind.

In this way, couples use shared nostalgia narratives to strengthen their emotional bonds – recalling their first date during an anniversary, or looking fondly at holiday photos. Mental time travel is also important for children, i.e. thinking about past things that were fun. Positive childhood memories can be stored for life, providing something to cherish and return to at will.

Nostalgia reconnects us to older parts of ourselves, important pieces of our own life story, helping to maintain identity.

The Upside of Nostalgia

Toward the end of the 20th century, nostalgia’s standing shifted again. It may be pathological in some cases; indeed, compulsively reliving bittersweet memories does obstruct the present. But creatively reconstructing one’s experiences is a universal phenomenon, and can be a survival tool.

Wildschut’s fellow researcher, Constantine Sedikides, is convinced that “nostalgia grounds you. It gives you a base on which to evaluate the present as a temporary state, and in doing so it perhaps builds resilience.” Nostalgizing helps people grow deeper life roots: feeling a connection between one’s past and one’s present shores up self-continuity, they wrote in the Review of General Psychology in October. Above all, it supplies a reservoir of meaning, i.e. the sense that one’s life is significant, purposeful, and coherent.

So now nostalgia has become the therapy rather than the problem, a “nourishing and invigorating psychological resource,” according to Wildschut and Sedikides. At the universities of Southampton and Utrecht, they have been pioneering a field of empirical research joining psychology, sociology and political science, with participants across 18 cultures and 5 continents.

Working the Past to Master the Present

The latest science shows that nostalgia is an adaptive emotional response to stress or change, that can take the sting out of the sense of loss. Although time is irreversible, the goodness that once was serves as an incentive for the present. By helping us recapture moments when life felt secure and contented, it can even weaken loneliness and alienation. This insight has led to the emergence of nostalgia-based therapy and the hope that “nostalgia inducement” could one day tackle such hard nuts as clinical depression, post-traumatic stress, and early-stage Alzheimer’s disease.

So from its original sense as a formal name for longing for home, nostalgia more broadly became longing for one’s past. But in the meantime, the stigma has been dissolved. Scientists now widely see it as a fundamental, universal emotion. They are still debating its pathological forms, those that keep us marooned in the past, but have shifted focus to its therapeutic value in the present.

Acknowledgment: Krystine Batcho’s beautifully-written “Nostalgia: The Bittersweet History of a Psychological Concept”, History of Psychology journal (May 2013)