Nicotine

The AAN study also discovered that nicotine can help improve cognitive memory, short-term memory, and working memory.  People undergoing nicotine therapy not only recall more facts, figures, and memories, but they recall them more quickly and clearly, as well.  By late 2013, the magazine Scientific American published an article by Professor Jennifer Rusted, experimental psychologist at Sussex University in Great Britain.  Rusted gained the attention of the worldwide scientific community by stating, “To my knowledge, nicotine is the most reliable cognitive enhancer that we currently have, bizarrely.” ... 
... The FDA and the CDC are not the only people who are aware of the secret health benefits of nicotine.  Back in the 1990’s, drug companies like Pfizer and Bristol-Meyers Squibb discovered that electronic vaping devices are a cheap way for patients to ingest certain medications. They also help the patient feel the effects of the drugs almost instantly. So why would Big Pharma, the CDC, and the FDA be attempting to paint e-cigs and vaping devices as “tobacco products” instead of “nicotine products?”   To answer that question, all we need to do is follow the money.
-- Matt Rowland, 2016