Has there been similar research done on the lingering effects of marijuana use by pilots?
Yes. Air Force did the studies. Motor skills are reduced every bit as much as alcohol and for a similar period. The reason for the similarity is that the body excretes both substances at similar rates. My last AF flight physiology course covered the similarities in detail. The real danger is that a person can feel perfectly fine after alcohol or pot use at ground level but the minute effects are amplified many times over at higher altitudes. The regulations are being rewritten on many aspects of altitude, including minimum altitude for oxygen use, etc.