Amsterdam, 6 april 2025– In 1972, French scientist Michel Siffre conducted a radical experiment by isolating himself in a dark cave 440 feet underground for 180 days. He aimed to understand the relationship between the human mind and time, hypothesizing that extreme conditions could unlock insights into human biology.
Siffre entered the cave without clocks, sunlight, or human contact, relying solely on hunger and fatigue to dictate his routine. Initially, he attempted to maintain a schedule, but his perception of time began to distort, leading to hallucinations, paranoia, and a chaotic mental state.
His team monitored his activity from above ground, discovering that by the second month, Siffre’s internal clock had drastically slowed. He believed only 24 hours had passed when nearly 48 had gone by, resulting in a new rhythm of 36 hours awake and 12 hours asleep. This was more than shocking, as it demonstrated the brain’s ability to create its own time system independent of natural light.
However, the isolation took a severe toll on his mental health. Siffre experienced memory loss, emotional swings, and a profound sense of loneliness.
After 180 days, he emerged, believing only 151 days had passed, and was stunned to learn the truth. His experiment revealed that without external cues, the brain loses track of time, transforming our understanding of time perception.
Siffre’s findings influenced research on circadian rhythms, space exploration, and mental health in solitary confinement. Despite enduring permanent memory loss and long-term mental health challenges, he continued his research, isolating himself in other caves to further explore his theories.
His work laid the groundwork for modern sleep science and time psychology, raising fundamental questions about the nature of time as both an external construct and a mental creation.
Siffre’s legacy serves as a reminder of the resilience and fragility of the human brain and how isolation can profoundly affect our inner world.
Loneliness is far more than just a bad feeling—it harms both individual and societal health. It is associated with a greater risk of cardiovascular disease, dementia, stroke, depression, anxiety, and premature death. The mortality impact of being socially disconnected is similar to that caused by smoking up to 15 cigarettes a day,4 and even greater than that associated with obesity and physical inactivity. And the harmful consequences of a society that lacks social connection can be felt in our schools, workplaces, and civic organizations, where performance, productivity, and engagement are diminished. Given the profound consequences of loneliness and isolation, we have an opportunity, and an obligation, to make the same investments in addressing social connection that we have made in addressing tobacco use, obesity, and the addiction crisis. An American study and Surgeon General’s Advisory shows us how to build more connected lives and a more connected society.
