Blinded experiment in the context of Placebo effect

Alternative medicine refers to practices that aim to achieve the healing effects of conventional medicine, but that typically lack biological plausibility, testability, repeatability, or supporting evidence of effectiveness. Such practices are generally not part of evidence-based medicine. Unlike modern medicine, which employs the scientific method to test plausible therapies by way of responsible and ethical clinical trials, producing repeatable evidence of either effect or of no effect, alternative therapies reside outside of mainstream medicine and do not originate from using the scientific method, but instead rely on testimonials, anecdotes, religion, tradition, superstition, belief in supernatural "energies", pseudoscience, errors in reasoning, propaganda, fraud, or other unscientific sources. Frequently used terms for relevant practices are New Age medicine, pseudo-medicine, unorthodox medicine, holistic medicine, fringe medicine, and unconventional medicine, with little distinction from quackery.

Some alternative practices are based on theories that contradict the established science of how the human body works; others appeal to the supernatural or superstitions to explain their effect or lack thereof. In others, the practice has plausibility but lacks a positive risk–benefit outcome probability. Research into alternative therapies often fails to follow proper research protocols (such as placebo-controlled trials, blind experiments and calculation of prior probability), providing invalid results. History has shown that if a method is proven to work, it eventually ceases to be alternative and becomes mainstream medicine.

A hierarchy of evidence, comprising levels of evidence (LOEs), that is, evidence levels (ELs), is a heuristic used to rank the relative strength of results obtained from experimental research, especially medical research. There is broad agreement on the relative strength of large-scale, epidemiological studies. More than 80 different hierarchies have been proposed for assessing medical evidence. The design of the study (such as a case report for an individual patient or a blinded randomized controlled trial) and the endpoints measured (such as survival or quality of life) affect the strength of the evidence. In clinical research, the best evidence for treatment efficacy is mainly from meta-analyses of randomized controlled trials (RCTs) and the least relevant evidence is expert opinion, including consensus of such. Systematic reviews of completed, high-quality randomized controlled trials – such as those published by the Cochrane Collaboration – rank the same as systematic review of completed high-quality observational studies in regard to the study of side effects. Evidence hierarchies are often applied in evidence-based practices and are integral to evidence-based medicine (EBM).

A placebo (/pləˈsiːboʊ/ plə-SEE-boh) can be roughly defined as a sham medical treatment. Common placebos include inert tablets (like sugar pills), inert injections (like saline), sham surgery, and other procedures.

Placebos are used in randomized clinical trials to test the efficacy of medical treatments. In a placebo-controlled trial, any change in the control group is known as the placebo response, and the difference between this and the result of no treatment is the placebo effect. Placebos in clinical trials should ideally be indistinguishable from so-called verum treatments under investigation, except for the latter's particular hypothesized medicinal effect. This is to shield test participants (with their consent) from knowing who is getting the placebo and who is getting the treatment under test, as patients' and clinicians' expectations of efficacy can influence results.

Deep brain stimulation (DBS) is a type of neurostimulation therapy in which an implantable pulse generator is surgically implanted below the skin of the chest and connected by leads to the brain to deliver controlled electrical impulses. These charges therapeutically disrupt and promote dysfunctional nervous system circuits bidirectionally in both ante- and retrograde directions. Though first developed for Parkinsonian tremor, the technology has since been adapted to a wide variety of chronic neurologic disorders.

The exact mechanisms of DBS are complex and not fully understood, though it is thought to mimic the effects of lesioning by disrupting pathologically elevated and oversynchronized informational flow in misfiring brain networks. As opposed to permanent ablation, the effect can be reversed by turning off the DBS device. Common targets include the globus pallidus, ventral nuclear group of the thalamus, internal capsule, and subthalamic nucleus. It is one of the few neurosurgical procedures that allows blinded experiments, although most studies to date have not taken advantage of this discriminant.