Scientists Find the First Evidence That LSD Synchronises Couples’ Brains
By Tommaso Barba, MSc, PhD
Research Scientist, Centre for Psychedelic Research, Imperial College London
A new study recorded both partners’ brains at the same time and found something no psychedelic experiment had shown before: LSD changed the way two romantic partners’ brain activity moved together. The most surprising part was when the effect appeared.
People who take psychedelics together often reach for the same language afterwards. They were ‘on the same wavelength’. They understood each other without speaking. The boundary between ‘me’ and ‘you’ felt less solid.
For years, descriptions like these have sat in an awkward place between personal testimony and science. Feeling profoundly connected to someone does not mean two brains have merged. But a new experiment asked a more interesting question: when two people feel unusually connected under a psychedelic, is there anything measurable happening between their brains?
Researchers at Maastricht University brought 25 romantic couples into the lab, gave both partners LSD, and recorded electrical activity from both brains at the same time. The study found the first evidence that a psychedelic changes brain-to-brain coupling between two people. The result was not a vague increase in similarity caused by two people taking the same drug.
The strongest effect belonged to the real romantic partner and depended on both brains being measured at the same moment. Then came the part no one would have predicted. The clearest synchrony did not appear while couples held hands, stared into each other’s eyes, or worked together. It appeared while they sat quietly, separated by a screen, doing almost nothing.
“This study is the first demonstration that a psychedelic might influence brain-to-brain synchrony between two people.”
The Problem With Studying Connection One Brain at a Time
Psychedelic science has spent decades asking what these drugs do inside an individual brain. That approach has taught us a great deal about perception, selfhood, emotion and brain connectivity. Yet it creates a strange blind spot when the experience being studied is social connection. Psychedelics often change how people relate to others. Studies report increases in emotional empathy, openness and feelings of connectedness. In clinical research, changes in connection to oneself, other people and the wider world have been proposed as part of the therapeutic process. (Preller & Vollenweider, 2019; Watts et al., 2017)
Most of this work still studies one participant at a time. A person lies in a scanner, looks at faces on a screen, answers questions or thinks about someone who is not in the room. However, a relationship unfolds through continuous feedback. Your partner’s expression changes your response. Your response changes theirs. Tone, timing, touch, eye contact and expectation all shape what happens next. The phenomenon lives between people, not inside one person alone.
A growing field called second-person neuroscience tries to study this directly. One method, known as hyperscanning, records neural activity from two people at once. Researchers then look for forms of inter-brain synchrony, moments when patterns in one person’s brain become statistically coupled to patterns in another’s. (Redcay & Schilbach, 2019)
This does not mean two people share thoughts or become one mind. It means some features of their neural activity rise, fall or change together over time. Previous research has linked this kind of coupling with cooperation, coordination, empathy and touch. But no one had tested what happens when two people share a psychedelic state.
A Living Room, Two EEG Caps and 50 Micrograms of LSD
The Maastricht team recruited 25 couples who had been together for at least six months. Everyone had previous experience with classic psychedelics and each couple came to the laboratory twice. On one day, both partners received 50 micrograms of LSD. On the other, both received a placebo. The order was randomised, and the sessions were separated by at least two weeks. The dose was high enough to produce a clear psychedelic state while leaving participants able to interact and follow instructions.
During the peak of the psychedelic experience, both partners wore 32-channel EEG caps. Their brain activity was recorded simultaneously while they moved through three kinds of situations. First, they rested for eight minutes, alternating between eyes open and eyes closed, with a visual barrier between them.
Next came a cooperative drawing task using a sketch. At one point, both partners controlled the same device, one moving the stylus horizontally and the other vertically. Finally, they held hands, made eye contact, or did both. Across the day, participants repeatedly rated how they felt about their partner. Blood samples also tracked how much LSD was circulating in the body.
The Psychedelic Faded. The Feeling of Connection Did Not.
The subjective results were broad. Under the psychedelic LSD, participants reported feeling more loving, connected, close, trusting, attached, committed, safe, attracted to their partner and ‘in sync’. Loneliness fell.
Interestingly, general feelings of sociability did not significantly change. Participants were not simply reporting a general desire to be around people. The shift was centred more specifically on the relationship in front of them. The timeline added another surprise. The concentration of LSD in the blood rose, peaked and then declined. Ratings of how strongly participants felt the drug followed a similar curve. Connectedness followed a different trajectory. It increased and then stayed elevated across the session, even as plasma LSD and the feeling of being high were falling. Seven hours after dosing, participants still reported feeling more connected to their partners.
This does not show that the relationship itself changed after the experiment. The study was not designed to answer that. It does suggest, however, that feeling connected was not simply another way of saying ‘I feel more intoxicated’. The social experience developed on a different timeline from the psychedelic LSD immediate intensity.
Were Their Brains Really ‘On the Same Wavelength’?
The clearest neural result from the LSD involved theta activity, a relatively slow electrical rhythm in the brain. Theta rhythms have been linked to processes such as attention, memory and emotional regulation, but they are also increasingly implicated in social cognition. Studies have connected theta activity with monitoring other people, coordinating behaviour and adjusting our responses during social interaction. In other words, theta seems to be one of the rhythms involved when the brain is tracking and adapting to another person.
The researchers measured whether the strength of theta activity in one partner rose and fell in step with the strength of theta activity in the other. Under the psychedelic LSD, this amplitude coupling increased between romantic partners during rest.
The effect was strongest when the couples had their eyes closed. There is an obvious alternative explanation. LSD changes EEG activity. Give two people the same drug, at the same dose, in the same room, and perhaps their brain signals start looking more alike for purely pharmacological reasons. The researchers tested this directly. They created artificial couples by pairing each participant’s EEG with recordings from people in other couples who had also taken LSD under the same conditions. If the drug alone explained the synchrony, these unrelated pairs should have shown the same effect.
They did not.
The team then kept each real couple together but shifted one partner’s EEG forward in time. The two recordings still came from the same people, the same drug session and the same environment. What disappeared was the moment-to-moment alignment between the two signals. The coupling collapsed again. Together, these controls suggest that the effect was partner-specific and contemporaneous. It was not simply ‘two brains on LSD’. It depended on these two people, at this particular moment.
The Surprising Finding: Brain Synchrony During Quiet Rest
If you had to guess when two romantic partners would show the most neural synchrony, the obvious candidates seem almost embarrassingly romantic: holding hands, looking into each other’s eyes, or cooperating on a shared task. Those were not the conditions that produced the clearest validated effect.
The strongest finding appeared during quiet moments of rest. The couples were not speaking, touching or looking at each other. A screen separated them.
Why would brain synchrony emerge more clearly when the couple was doing less? The study cannot tell us yet.
One possibility is that structured tasks pull attention outward. Trying to coordinate a drawing or deliberately maintain eye contact gives both people a goal. Quiet co-presence leaves more room for spontaneous internal and interpersonal dynamics to unfold. There was also a revealing detail during the eye-contact condition. Under the psychedelic LSD, couples often laughed, but they frequently laughed at different moments. A situation that looked intimate from the outside did not necessarily produce tightly coordinated behaviour.
Another possibility is that the resting period captured a residue of what had already happened between the partners. Research outside psychedelics suggests that social interaction sometimes leaves a temporary trace in inter-brain coupling even after the interaction ends. If so, the quiet period might have made an accumulated relational effect easier to detect. (Shamay-Tsoory et al., 2024)
Did Couples With Greater Brain Synchrony Feel Closer?
Exploratory analyses offered one more intriguing result. Couples with greater resting theta amplitude coupling under LSD also tended to report stronger subjective connectedness.
The association was moderate, with a correlation of 0.49. It was absent under placebo. However, the association did not survive correction for multiple statistical comparisons. The authors therefore treat it as hypothesis-generating, not as a confirmed link between synchronised brains and stronger love or closeness.
A second exploratory result pointed in the opposite direction from a simple intoxication explanation. Greater resting coupling was associated with lower subjective drug intensity, rather than higher intensity. That relationship also needs replication.
Could Psychedelics Change the Plasticity of Relationships?
The broader idea raised by the study is less about synchrony itself and more about where psychedelic effects might occur.
Psychedelics are often discussed as temporarily increasing plasticity, making the brain more responsive to information and experience. Most versions of this idea stop at the boundary of the individual.
Relationships have patterns too. Partners learn how to interpret each other. A tone of voice begins to predict criticism. One person withdraws, the other pursues. A familiar facial expression is read before either person has consciously thought about it. Over time, these patterns become fast and automatic.
One possibility is that psychedelics temporarily alter the flexibility of these interpersonal patterns as well. LSD acts strongly through the serotonin 2A receptor, which is involved in psychedelic changes in brain connectivity and social processing. Animal work also suggests that psychedelics alter social behaviour and reopen periods of heightened social reward learning. (Preller et al., 2018; Duerler et al., 2020; De Gregorio et al., 2021; Nardou et al., 2023)
The new study does not prove that a psychedelic makes relationships more plastic. It offers a first neural clue that the effects of a shared psychedelic state might extend beyond changes occurring inside one nervous system.
That distinction matters for therapy. If interpersonal context shapes psychedelic experience more strongly during these states, then who is present, how safe a person feels, and what unfolds between people may form part of the mechanism rather than serving as background. (Wagner et al., 2021; Cornelius & Barba, 2026)
What This LSD Study Does Not Show
There are important limits to this study. The sample was small, young, healthy and already experienced with psychedelics. These were established couples, not couples seeking treatment for relationship problems.
The experiment also struggled with blinding, as psychedelic studies often do. Participants made 95 guesses about whether they had received LSD or placebo. Ninety-three were correct. Expectations therefore remain a plausible contributor to the self-report findings.
The neural finding was also much narrower than the subjective effect. Feelings of connectedness increased broadly and stayed elevated for hours. The strongest partner-specific synchrony appeared only under particular resting conditions. Inter-brain synchrony should therefore not be treated as a neural meter for love, intimacy or relationship quality.Earlier work in romantic couples has even found situations where greater felt support coexists with lower inter-brain synchrony, another reason not to treat synchrony as a simple measure of closeness. (Djalovski et al., 2021)
The study does not show that LSD improves relationships. It does not show that couples should take psychedelics together. It does not tell us whether more neural synchrony is beneficial. Increased interpersonal sensitivity might support closeness in one context and amplify conflict or vulnerability in another.
What Psychedelics For Couples May Look Like Outside The Lab
Beautiful Space works with this question in practice. Couples go through a psilocybin programme together, with preparation sessions before the psilocybin day and integration sessions in the weeks after it. Beautiful Space and researchers at Imperial College London have been following these couples, measuring how close they feel, how much they share the same view of the world and how intimate their days are, before and after the session. Both partners were also interviewed about how the other had changed.
The Maastricht results add something to think about here. The strongest synchrony did not show up during hand-holding or eye contact. It showed up when couples were simply sitting in the same room. If that finding holds, the quiet time a couple spends together around a psilocybin session may matter more than we tend to assume.
The Next Frontier in Psychedelic Neuroscience May Be Between Brains
For decades, psychedelic neuroscience has asked what happens when a drug changes one brain.
This experiment asks a different question: what happens when two people share the state, and the relationship itself becomes part of what is being measured?
That shift matters because psychedelic experiences do not happen in isolation. They unfold in rooms, relationships and social worlds. The person beside you might influence the experience in ways that become visible not only in what you report feeling, but in the dynamics of your nervous system.
Twenty-five couples are nowhere near enough to rewrite our understanding of human connection. But the study opens a new scientific direction.
The phrase ‘on the same wavelength’ is still a metaphor. But for the first time, psychedelic researchers found a measurable signal sitting somewhere behind it.
About the Author
Tommaso Barba
Tommaso Barba is a PhD research scientist at the Centre for Psychedelic Research at Imperial College London. His research explores the effects of psychedelic compounds on the brain, well-being, and human flourishing, with particular interest in short-acting psychedelics such as 5-MeO-DMT.
His work also investigates the potential role of psychedelic substances in relationships, intimacy, and sexual well-being. Tommaso authored the first research study examining the long-term effects of psychedelic use on sexual functioning.
He is currently involved in the world’s first naturalistic research study exploring the impact of psilocybin combined with psychological support on relationship wellbeing in collaboration with Beautiful Space.
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