This chapter highlights the recent burst of controlled, scientific research on medical and nonmedical uses of psychedelic drugs and MDMA to improve individual welfare, and argues that this research should be extended to couples in romantic relationships. It questions the line between "drugs" and "medicine" and argues that such distinctions often reflect dubious social and historical factors, rather than a clear-eyed assessment of actual benefits and harms. It introduces the idea that love drugs might help strengthen certain relationships, and that anti-love drugs might help other relationships end. But there are serious risks that might be associated with such drugs, and the wider social implications will be hard to predict. To minimize this risk and uncertainty, careful ethical deliberation and nuanced policy measures will be key.

What are love drugs? Basically, they are drugs that affect love—or romantic relationships, more broadly. This chapter begins with an account of drugs, explaining that they are essentially just chemicals—clusters of molecules that work on the brain to produce certain effects—and that our choice to regard them as medicine versus recreation, or as a means to personal or spiritual development, is up to us. It is a question of values. The chapter then gives an account of love, explaining that it has both biological and psychosocial dimensions. When there is a tension between love and well-being, it may make sense in certain cases to intervene in either or both of those dimensions (biological, psychosocial) to improve our relationships and our lives.

Why might tensions arise between love and well-being? Sometimes there can be painful inconsistencies between our conscious values surrounding love, the prevailing cultural norms or social scripts for romantic partnerships in our environment, our subjective experiences of attachment and desire, and our underlying biological natures. Which of these dimensions can be altered? Which of them should be altered, and under what conditions? Many societies hold up monogamous marriage as the ideal for committed relationships. Is this ideal consistent with human nature? This chapter argues that there is no single answer to that question: natural variation among individuals and at the level of the species confounds such one-size-fits-all thinking. Accordingly, if biological interventions—in addition to psychosocial ones—will ever help love and happiness coincide, it will depend on the specific issues facing a given couple.

This chapter gets specific about the kinds of biological interventions into love that are currently possible—and those that may exist in the future. It shows how love can be affected by certain chemicals through a variety of different pathways, depending on the psychosocial context. It also discusses common medications that may already be influencing love and relationships, such as hormonal birth control and antidepressant pills, and argues for a shift in scientific research norms: away from an exclusive focus on individuals and clinical symptoms, and toward a more inclusive, relationship-oriented paradigm that considers the interpersonal and social implications of drug-based medical treatments.

If love drugs become more widely available, who should use them? This chapter introduces Stella and Mario, a married couple with dependent children. The couple are in a "gray" relationship—that is, a relationship that is not violent, abusive, or otherwise clearly dysfunctional, but which has lost its romantic spirit, despite many earnest attempts to keep it alive. The couple are unhappy. They are considering a divorce. They worry about how this might affect the children. They do still care about each other and value what they have built together. But they've run out of places to look for a shared sense of joy. The chapter argues that this is a very common situation for long-term partners, and that love drugs may soon be a viable option for supporting couples' mutual well-being within such relationships.

Drug-supported couples therapy is not a new phenomenon. In fact, MDMA was widely used for this purpose, to good effect in many cases, into the 1980s—before it was banned, largely for political reasons. This chapter discusses the history of MDMA-assisted psychotherapy, making clear that MDMA is not just "emotional glue" that holds romantic partners together no matter how incompatible they may be. Rather, professionally guided, drug-enhanced counseling may help some individuals or couples realize that they need to end their relationship, and may allow them to do so in a more loving and healthy way. The chapter asks whether MDMA poses a threat to authenticity or personal identity, and raises other risks that may be associated with its use under certain conditions. It concludes with a call for careful, controlled scientific research into the potential of MDMA as an aid to couples counseling.

Why are there are so many couples looking for help in the first place? Why is it so hard to make long-term, romantic partnerships work, much less flourish? This chapter argues that at least part of the explanation may lie in a disconnect between our ancient, evolved dispositions for mating and attachment, and the social and physical environment we have created through culture and technology. In short, our capacity for love did not evolve to support lifelong relationships in contemporary societies. Rather, it evolved to support our ancestors' reproductive success under social conditions that for the most part no longer exist. In addition, the place of love in marriage—and the institution itself—has undergone a whiplash-inducing transformation over the past 200 years, leaving us ill-equipped to fit the pieces together. Is there a role for chemical treatments in strengthening attachment bonds directly?

One of the most hyped possibilities for chemically strengthening love and attachment directly is the hormone oxytocin. This chapter surveys the evidence for oxytocin-enhanced relationships and identifies a number of gaps in the literature that would need to be filled before oxytocin could be used as a love drug. If stronger evidence comes out supporting real-world effectiveness of oxytocin in a relationship context, clear guidelines would need to be put in place to ensure that it was used responsibly and ethically. Building on this insight, the chapter concludes with an outline of key ethical constraints that should apply to any drug-assisted mode of couples therapy.

Instead of trying to strengthen a relationship, what if the relationship needs to end? This chapter discusses existing drugs that may be capable of diminishing love, lust, attraction, or attachment to a current romantic partner. It also raises concerns about possible negative outcomes and points to the limits of what is likely to be possible. Given that drugs or medications used for other purposes may have anti-love side effects, what would be the ethics of prescribing them off-label as a way of assisting with a difficult breakup or healing a broken heart? The chapter concludes by acknowledging the risk of "pathologizing" love and romantic relationships by intervening in them with medical substances, and suggests a way to avoid this particular worry.

Who could benefit from using anti-love drugs, and what are the most serious ethical concerns raised by the prospect of a chemical breakup? This chapter identifies several cases where the use of a drug—in combination with appropriate psychosocial measures—might be justified as a way of blocking or degrading love, lust, attraction, or attachment: for example, victims of intimate-partner violence who want to sever a feeling of addiction to their abuser; individuals with pedophilia who risk causing harm to children and who need help to control their urges; people suffering from unrequited love leading to suicidal thoughts or tendencies. By working through these and other case studies, the chapter develops a set of ethical conditions for the responsible use of anti-love biotechnology.

Anti-love drugs could easily be misused. They bring to mind disturbing parallels with sexual orientation conversion therapies and other attempts to coercively intervene in the biology of vulnerable minorities, such as LGBTQ children and adolescents. This chapter explores the dangers of making certain biotechnologies available under oppressive conditions or in societies characterized by widespread intolerance or injustice. It also questions the logic of the "born this way" movement for LGBTQ rights, which is premised on the idea that sexual orientation is not a choice. If high-tech conversion therapies are ever developed that can in fact change sexual orientation, the intellectual foundation for the movement would collapse. The chapter therefore argues for the movement to be placed on stronger footing, and suggests how this might be done.

This final chapter has two main goals: to address lingering worries about the medicalization of love—that is, bringing love and relationships into the domain of medicine in a way that threatens to undermine their value—and to put forward a positive vision of love as something we can partially choose, or improve, through science and technology. Will knowing how love works, and even shaping it through hormones and chemistry, rob it of its importance in our lives? Or will it empower us to make our most intimate relationships more reliably consistent with real human flourishing?

So much of our lives has been subsumed by drugs and medicine: do we really need another "pill" to add to the mix? This brief epilogue argues that the answer is, actually, no. We need fewer, but better drugs—drugs with less severe side effects and more power to genuinely improve our well-being. The potential of MDMA and some psychedelics to replace a range of harmful medications is discussed, with a renewed call for high-quality research into this possibility as applied to relationships.