The research literature, while copious, is messy and varied: methodologies and devices vary substantially, sample sizes are tiny, the study designs vary from paper to paper, metrics are sometimes comically limited (one study measured speed of finishing a RAPM IQ test but not scores), blinding is rare and unclear how successful, etc. Relevant papers include Chung et al 2012, Rojas & Gonzalez-Lima 2013, & Gonzalez-Lima & Barrett 2014. Another Longecity user ran a self-experiment, with some design advice from me, where he performed a few cognitive tests over several periods of LLLT usage (the blocks turned out to be ABBA), using his father and towels to try to blind himself as to condition. I analyzed his data, and his scores did seem to improve, but his scores improved so much in the last part of the self-experiment I found myself dubious as to what was going on - possibly a failure of randomness given too few blocks and an temporal exogenous factor in the last quarter which was responsible for the improvement.

The fact is, many of these compounds in small amounts and less frequent use can be relatively safe, but as you’re probably not surprised to hear, I’m not 100% convinced of the overall long-term safety or efficacy of most smart drugs used frequently or in moderate to high dosages for the reasons stated above. It is true that some are slightly less risky than others and are increasing in popularity among biohackers and medical professionals. They’re also becoming used with high frequency by students, athletes and e-gamers, three populations for which smart drug “doping control” is becoming more frequently banned and considered to be illegal use of performance-enhancing drugs. Yes, “brain doping” and “brain PED’s” (brain Performance Enhancing Drugs) are now a thing. But I’d consider carefully the use of smart drugs as daily go-to brain enhancing supplements, especially in light of the safer alternative you’re about to discover: the entire category of natural and synthetic nootropic compounds.
The use of prescription stimulants is especially prevalent among students.[9] Surveys suggest that 0.7–4.5% of German students have used cognitive enhancers in their lifetime.[10][11][12] Stimulants such as dimethylamylamine and methylphenidate are used on college campuses and by younger groups.[13] Based upon studies of self-reported illicit stimulant use, 5–35% of college students use diverted ADHD stimulants, which are primarily intended for performance enhancement rather than as recreational drugs.[14][15][16] Several factors positively and negatively influence an individual's willingness to use a drug for the purpose of enhancing cognitive performance. Among them are personal characteristics, drug characteristics, and characteristics of the social context.[10][11][17][18]