Oxytocin – the so-called ‘love hormone’ – is known for its profound effects on mood and social behaviour. Once seen primarily as a maternal hormone, with a role to play in childbirth and breastfeeding, it is now the subject of a huge body of research. As successive studies have reinforced, oxytocin is associated with trust, empathy, sexual activity, romantic attachment and group bonding.
These magical-seeming properties have, unsurprisingly enough, piqued the attention of medical researchers. Oxytocin nasal sprays have been trialled for a large number of disorders, including social anxiety, depression, autism, drug addiction, PTSD, IBS and even obesity. You can also buy sprays online, which are somewhat tenuously billed as enhancing the user’s social skills.
Unfortunately, the field is littered with false starts and conflicting results. The hormone’s action within the body is complex, and occurs in the context of a broader neurochemical system. This makes it difficult to simulate its effects using a nasal spray. According to a 2015 review, “most of the reported positive findings regarding how OT [oxytocin] affects human behavior are likely to be false-positives”.
That doesn’t mean scientists are likely to give up on oxytocin just yet. It just means the early buzz surrounding the hormone has given way to more nuanced discussion around what might be accomplished and what needs to happen first.
Oxytocin for Alzheimer’s
One promising research avenue is oxytocin for Alzheimer’s disease. In July, scientists in Japan reported a breakthrough in vitro study. Using a mouse model, they found that oxytocin could reverse some of the nerve cell damage that occurs in the early stages of the disease.
According to a leading theory about Alzheimer’s, the disease occurs when a toxic protein called beta-amyloid begins to clump around neurons in the brain. The neurons degenerate, which leads to a decrease in synaptic plasticity and ultimately to cognitive decline. A mechanism called long-term potentiation (LTP), which allows nerve cells to encode memories, is blocked.
The researchers, from Tokyo University of Science and Kitasato University, took slices of mouse brain on a dish, and perfused the cells with beta amyloid to confirm that LTP inhibition did occur. Next, they perfused the cells with oxytocin and found that the damage was reversed. They also performed a follow-up experiment to show that oxytocin was indeed the chemical responsible.
“Although oxytocin has been reported to participate in regulating learning and memory performance, no [previous] report has clarified its effects on the beta amyloid-induced impairment of synaptic plasticity,” says lead study author Professor Akiyoshi Saitoh, from Tokyo University of Science.
“We found that oxytocin could reverse the effects of beta amyloid on mice hippocampal LTP in an in vitro study. Now, we have examined the effects in an in vivo study. In the near future we will be able to publish our behavioural data.”
While much more research is needed – beginning with a proof of concept in animal models – Saitoh is hopeful that oxytocin could be used as an Alzheimer’s treatment further down the line.
“We suggest the interesting possibility that oxytocin should be a completely novel therapeutic modality for the treatment of memory loss associated with cognitive disorders,” he says.
Oxytocin for autism
Oxytocin has also been indicated as a treatment for the social difficulties associated with autism spectrum disorders (ASD). For both autistic and non-autistic people, higher levels of oxytocin appear to correlate with better performance in social tasks. It seems plausible that administering artificial oxytocin would help people who struggle in this area.
As has been the case with a lot of oxytocin research, however, the studies have shown mixed results. On the one hand, oxytocin sprays have been shown to improve some aspects of social functioning in ASD, including emotion recognition and eye contact.
On the other, these studies tended to involve a one-off dose of oxytocin, rather than long-term daily treatments. Studies involving longer-term treatments have not been conclusive.
That said, there have been some promising findings, and additional clinical trials are underway. Researchers are also trying to find out how the hormone operates within the brains of those with ASD, as per a 2019 study that analysed post-mortem brain tissue. This study measured oxytocin receptors in certain regions of the brain and found differences among those with autism.
There is also a promising strand of research that focuses on oxytocin as an adjunct to psychotherapy. The idea is that the oxytocin might increase the bond between client and therapist, and boost the effectiveness of the treatment.
German psychiatrist Rene Hurlemann, along with Simone Shamay-Tsoory from Haifa University, are trialling oxytocin plus group psychotherapy for loneliness. In their previous research, they found that lonely people had the same baseline oxytocin levels as controls. This changed when subjects were asked to think about a happy memory – controls saw a rise in oxytocin, but lonely people did not.
Moving beyond psychiatric and neurological conditions, oxytocin might one day be used treat osteoporosis. In a recent study on rats, ageing female rats were given oxytocin. Unlike the control group, they did not lose any bone density, possibly because the hormone mediates the action of oestrogen in bones.
What seems to be clear across the board is that different people respond to oxytocin in different ways, and we need to learn more about dosing, mechanism of action and a host of other variables. To give one particularly stark example – in a recent study, cocaine-addicted men benefited from oxytocin therapy but cocaine-addicted women did not.
“Although the role of OXT [oxytocin] in the modulation of social behavior is today indisputable, the field of OXT-based pharmacotherapy is filled with many small trials that report incongruent results,” wrote the authors of a recent mini-review article, published in Frontiers in Psychiatry. “Efforts should be made to understand its neurobiological mechanism of action and effect based on individual variability in underlying neuropeptide biology.”
In short, while oxytocin has clear therapeutic potential, there are key questions that remain unanswered. And until we understand precisely how it works in the body, we may struggle to repurpose it as a drug.