Folie à Deux, or How Two People Build Shared Delusions

The new film, "Joker," imagines how shared delusions isolate couples from reality.

Reviewed by Michelle Quirk

Key points

• No longer a formal diagnosis, some clinicians still use folie à deux to understand toxic relationships.
• In extreme cases, shared delusions can lead to destructive behavior that seems logical only to the couple.
• Shared delusions may feel safer than reality, causing behavior that appears chaotic or harmful to others.

Two people can build powerful, intimate, and beautiful connections. But sometimes, that connection is rooted in the intense, shared delusions of two people—a folie à deux.

The subtitle of the latest film, Joker: Folie à Deux, has reignited interest in the concept, even though it's fallen out of favor as a formal diagnostic term. Yet some clinicians still find it useful for understanding how an intimate relationship can isolate two people from the rest of the world.

The concept of folie à deux relationships provides insight into how reality and fantasy are constructed in the process of building relationships. Intense communication, particularly when it becomes increasingly codependent and disconnected from reality, can deepen intimacy but, in the most extreme cases, may also lead to shared delusions.

It is relatively common for people to get drawn into toxic groups, but there’s something uniquely intense about a two-person fantasy world. The fantasy can start innocently, subtly, and even jokingly: Shared fears and anxieties feed off each other. Both people validate and amplify the other’s worst suspicions and fears.

Each partner reinforces and stokes the other’s worst fears until the shared fantasy starts to feel safer and more seductive than reality itself. As the pair continue to create an imaginary, detached view of the world, their relationship becomes an echo chamber, with each person’s language and behaviour reinforcing the other’s distorted view of the world

In the most extreme cases, the couple becomes entangled in a dark fantasy that is extraordinarily difficult to disconnect from because the relationship is based on a shared, socially created, and reinforced delusion.

Language Structures Thought

Language plays a central role in shaping and maintaining how we view reality. Destructive groups like gangs, cults, and terrorist organizations create their own internal languages, reinforcing their worldview at the expense of individual identity and connections with outsiders.

Shared, but exclusive codes like words, symbols, or images may seem meaningless or bizarre to those outside the group, but they provide powerful meaning and belonging to insiders. For instance, symbols that are harmless to most might carry deep, dangerous significance within these groups.

In a folie à deux relationship, two people create their own symbols, their own interpretations of language, and code words. Building that shared reality together creates a sense of intimacy, of closeness and connection that binds them closer together, even if it takes them away from reality. It can happen slowly and incrementally, with each new event and shared experience being reimagined and reinterpreted from the lens of two people who move further and further from objective reality.

Not all shared realities are dangerous. Most healthy relationships thrive on them. Couples build their bond by developing a shared understanding of the world, but they also stay grounded by relying on social networks—friends, family, coworkers—to help balance their perspectives.

In most healthy relationships, the shared reality is flexible and can accommodate both the relationship and a wider network of relationships and interactions with the outside world. Inside jokes, private references, and subtle signals are the glue that strengthens intimacy over time.

When Does a Shared Reality Turn Toxic?

The problems arise when a couple’s shared reality becomes exclusive to their relationship, disconnected from anything or anyone else. What seems to work about their relationship only works between them but causes chaos everywhere else: and sometimes the chaos is what continually drives them back toward one another.

Their shared delusions become a way to make sense of a confusing, unpredictable world. Yet, from the perspective of everyone around them, they’re often the ones creating the chaos. Their increasingly erratic, unexplainable behavior that is destructive, even criminal, only makes sense inside the fantasy they’ve built. To everyone else, their actions seem baffling and dangerous.

A shared reality turns toxic when their private world becomes so insular that it isolates them from family, friends, and the capacity to function in any part of the world outside of the one they have created. They can start acting and thinking in ways that make sense within their shared fantasy but seem totally illogical in the context of wider social groups, relationships, and responsibilities.

Technology as an Amplifier

Digital communication makes it easier than ever for people to create shared realities, especially those rooted in fantasy or digital distortions. Technology amplifies this process by creating new spaces, worlds, and channels for people to connect from anywhere at any time. It also provides tools that filter out unwanted information or challenge to those realities. Noise-cancelling headphones, private messaging, and personalized social media feeds create echo chambers, where external voices are muted, and internal feedback loops become more intense.

Curated online communities can further isolate people, reinforcing their shared worldview and making it harder to connect with broader society. The constant, immediate reinforcement of virtual spaces accelerates the process of building and maintaining a self-contained reality. This is not inevitable, but the tools can be customized by the user, augmenting reality in any direction that is preferred.

Insights From Fiction

We can't diagnose fictional characters, but fiction gives us a different lens to understand people and relationships. It allows us to identify with characters, behaviours, and emotions we wouldn’t necessarily encounter in everyday life and may not want to experience firsthand. Fiction also gives us a language to talk about difficult issues or ideas in reference to imaginary characters and places. This can be a bit safer and easier than directly talking about the difficult issues in our own lives.

When two people create their own shared reality, it can be interesting, fun, and eccentric. All relationships are built on mutual understandings, which are not always perfectly accurate understandings of the world around them. It is rarely dangerous, but when they isolate people entirely from the outside world and reality, the consequences can be more troubling.