Nicotine-related beliefs induce dose-dependent responses in the human brain. Credit:Lily Armstrong-Davies, Medical Illustrator
Scientists, researchers, clinicians and others have long witnessed the benefits of the “placebo effect,” the fact that some patients' health improves after being given a placebo drug or treatment solely due to their belief in said treatment.
While the placebo effect has been studied, it’s still not quite understood.
“Beliefs can have a powerful influence on our behavior, yet their effects are considered imprecise and rarely examined by quantitative neuroscience methods,” said Xiaosi Gu, associate professor of psychiatry, and neuroscience at the Icahn School of Medicine at Mount Sinai, and senior author of a new study on the topic.
Gu and her team at Mt. Sinai set out to investigate if human beliefs can modulate brain activities in a way comparable to the dose-dependent effects of pharmacology. They found a high level of precision in how beliefs can influence the human brain, with implications across a range of applications.
For the study, published in Nature Mental Health, the researchers instructed nicotine-dependent study participants to believe that an electronic cigarette they were about to vape contained either low, medium or high strengths of nicotine, when in fact the level remained constant. Participants then underwent functional neuroimaging (fMRI) while performing a decision-making task known to engage neural circuits activated by nicotine.
The researchers found that the thalamus—an important binding site for nicotine in the brain—showed a dose-dependent response to the subject’s beliefs about nicotine strength. This effect was previously thought to apply only to pharmacologic agents.
According to the study results, a similar dose-dependent effect of beliefs was also found in the functional connectivity between the thalamus and the ventromedial prefrontal cortex, a brain region that is considered important for decision-making and belief states.
The research team says these results provide “compelling evidence” to support the relationship between subjective beliefs and biological substrates in the human brain. The results also impact a range of applications in pharmacology and neuroscience.
For example, if easily influenced, subjective beliefs could become a direct target for the treatment of substance use disorders—amid the worst, seemingly never-ending opioid crisis the U.S. has ever experienced. Beyond addiction, harnessing beliefs in a systematic manner could better serve overall mental health treatment.
The study results also give power to the idea that human beliefs can be used to enhance and optimize both pharmacological and nonpharmacological treatments for individuals.
Next, Gu and her team are interested in testing the effects of beliefs on drugs beyond nicotine, including addictive substances like cannabis and alcohol, as well as therapeutic agents like antidepressants and psychedelics.
“It would be fascinating to examine, for example, how the potency of a drug might impact the effect of drug-related beliefs on the brain and behavior, and how long-lasting the impact of those beliefs might be,” said Gu. “Our findings could potentially revolutionize how we view drugs and therapy in a much broader context of health.”