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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Biology of romantic love | 9/14 | https://en.wikipedia.org/wiki/Biology_of_romantic_love | reference | science, encyclopedia | 2026-05-05T15:53:39.742070+00:00 | kb-cron |
Modern research is increasingly showing the importance of endogenous opioids in love and social attachment, particularly the β-endorphin (the most potent endogenous opioid) and the μ-opioid receptor system. While opioids have their origin being the body's natural painkiller, they're also implicated in a variety of other systems, essentially like neurotransmitters. Opioid receptors are located throughout the brain, including in the limbic system (affecting basic emotions) and neocortex (affecting more conscious decision-making). Opioids are linked to the consummatory part of reward, or i.e. "liking" or pleasure, and released in areas of the brain called hedonic hotspots (or pleasure centers). Hedonic hotspots are located in the nucleus accumbens, the ventral pallidum and other areas. This function includes social reward, or the pleasurable aspect of social interactions. The brain opioid theory of social attachment (BOTSA) is a long-running theory summarizing this connection, originally formulated in the 1980s and 1990s, based on a proposal by the psychiatrist Michael Liebowitz and research by the neuroscientist Jaak Panksepp. Starting in the 1990s, opioids were overshadowed by the interest in oxytocin and largely overlooked until more recently, possibly because of the difficulty studying them (requiring e.g. a PET scan, which is expensive). Opioids have been connected to a variety of social experiences, including the early stage of romantic love and attachment styles. While the addictive aspects of love have been compared to cocaine or amphetamine addiction, other aspects may also resemble an opioid addiction. BOTSA (as it was originally conceived of) predicts that in the absence of social relationships, individuals will have comparatively lower levels of endogenous opioids, motivating them to initiate contact with other people. Social contact then leads to feelings of euphoria and contentment, but individuals also need to continue contact to avoid withdrawal symptoms. Liebowitz originally argued that romantic relationships resemble narcotic addiction and that individual neurochemical differences could also explain why some people are unable to commit, or stay in abusive relationships. Earlier experiments on BOTSA were animal studies, but in the 2000s this has been expanded to include human experiments. Among the animal studies which have been done, there is some evidence that separation distress is akin to opioid withdrawal. Studies on chicks, puppies, Guinea pigs, rats, sheep, and monkeys have shown that administrating morphine reduces distress vocalizations when separated from the mother, and administrating naloxone (an opioid antagonist) increases them, even in the presence of other members of the same species. In another study, mutant mouse pups with a μ-opioid receptor knockout (lacking the μ-receptor gene) vocalized less frequently in response to isolation than normal mice. Administration of morphine had no effect on distress vocalization frequency in the knockout mice, despite reducing it in normal mice. Furthermore, these knockout mice had a reduced preference for their mother's odor, which is normally the result of conditioning mediated by the endogenous opioid system. In nonhuman primates, studies have suggested that endogenous opioids provide the euphoria behind dyadic social grooming behaviors. Other animal studies have shown that endogenous opioids play a role in the desire for rough-and-tumble play (a physical, but also social behavior). In humans, physical activity with a social element (rowing, dancing, laughing) increased pain tolerance more when the activities were synchronized with other people. An fMRI experiment in 2010 investigated whether viewing a picture of a romantic partner could reduce pain sensitivity, and which areas of the brain became active. Participants were exposed to high temperatures (resulting in moderate or high pain levels) while viewing a picture of a romantic partner (whom they were intensely in love with), or a friend, or performing a word association task which has also been shown to reduce pain via distraction. Participants were then asked to rate how much pain they felt on a pain scale, and both viewing a romantic partner and performing the distraction task (but not viewing a friend) were found to reduce pain levels. The fMRI scans revealed that viewing a romantic partner activated reward circuits in the brain, while the distraction task did not. Brain areas were also correlated with pain relief to reveal that reward analgesia and distraction analgesia involved distinct areas. Some areas associated with sensory processing of pain also had decreased activity while viewing a romantic partner. An earlier experiment showed that viewing photos of a romantic partner reduced experimental pain, but did not pair it with a brain scan. A PET scan experiment in 2016 investigated whether non-sexual social touching between romantic partners was mediated by endogenous opioid activity. This study found that social touch did have an effect, but unexpectedly found that social touching decreased opioid activity in the brain rather than increasing it (despite being rated as pleasurable by participants). This is in contrast with prior PET research that pleasant affect is related to increased opioid activity. One possible explanation is that touching decreases stress, so this might also decrease the ongoing opioid activity in response to distress and pain. As this is also at odds (to some extent) with primate studies on grooming, there may be some variation between species in how opioids are involved with social reward. Other modern studies on humans include blood plasma levels, genetics and studies with drugs like morphine and naltrexone to see how they change social perception and behavior.
=== Obsessive thinking ===