Subjects with a history or presence of clinically important cardiac, renal, hepatic, endocrine (including diabetes mellitus), pulmonary, biliary, gastrointestinal, pancreatic, or neurologic disorders that, in the judgment of the Investigator, would interfere with the subject's ability to provide informed consent, comply with the study protocol (which might confound the interpretation of the study results), or put the subject at undue risk.
As discussed in my iodine essay (FDA adverse events), iodine is a powerful health intervention as it eliminates cretinism and improves average IQ by a shocking magnitude. If this effect were possible for non-fetuses in general, it would be the best nootropic ever discovered, and so I looked at it very closely. Unfortunately, after going through ~20 experiments looking for ones which intervened with iodine post-birth and took measures of cognitive function, my meta-analysis concludes that: the effect is small and driven mostly by one outlier study. Once you are born, it’s too late. But the results could be wrong, and iodine might be cheap enough to take anyway, or take for non-IQ reasons. (This possibility was further weakened for me by an August 2013 blood test of TSH which put me at 3.71 uIU/ml, comfortably within the reference range of 0.27-4.20.)
When Giurgea coined the word nootropic (combining the Greek words for mind and bending) in the 1970s, he was focused on a drug he had synthesized called piracetam. Although it is approved in many countries, it isn’t categorized as a prescription drug in the United States. That means it can be purchased online, along with a number of newer formulations in the same drug family (including aniracetam, phenylpiracetam, and oxiracetam). Some studies have shown beneficial effects, including one in the 1990s that indicated possible improvement in the hippocampal membranes in Alzheimer’s patients. But long-term studies haven’t yet borne out the hype.
Drugs such as Adderall can cause nervousness, headaches, sleeplessness and decreased appetite, among other side-effects. An FDA warning on Adderall's label notes that "amphetamines have a high potential for abuse" and can lead to dependence. (The label also mentions that adults using Adderall have reported serious cardiac problems, though the role of the drug in those cases is unknown.) Yet college students tend to consider Adderall and Ritalin as benign, in part because they are likely to know peers who have taken the drugs since childhood for ADHD. Indeed, McCabe reports, most students who use stimulants for cognitive enhancement obtain them from an acquaintance with a prescription. Usually the pills are given away, but some students sell them.
The use of cognition-enhancing drugs by healthy individuals in the absence of a medical indication spans numerous controversial issues, including the ethics and fairness of their use, concerns over adverse effects, and the diversion of prescription drugs for nonmedical uses, among others. Nonetheless, the international sales of cognition-enhancing supplements exceeded US$1 billion in 2015 when global demand for these compounds grew.