Interesting that people refer to 'Flashbacks'.
The evidence suggests that any 'flashback' is a memory response triggered by audio/visual illusions to which we are all subject. It is because the user has had heightened awareness to these phenomena during their drug-experience/fix, that when they see them once 'sober', they associate this with their drug experience.
There was no evidence (at least by 1994) that any drug remains in the brain long enough to cause symptoms long after the event. Lots of false information on that subject propelled by poorly educated 'authorities'.
Longer-term effect of Psychadelic/stimulant drugs is unknown. Lots of talk of altering brain structure. Not good news for those who've taken NAPS, or inhaled pesticides,or eaten unwashed vegetable/fruit produce. All these contain chemicals that act on the brain synapses in similar ways to the above drugs. Gulf War Syndrome? BSE/CJD anyone??
Interestingly, cannabis abuse (and I'm talking habitual heavy use here) can have devastating effects on the individual. I know of an individual who has been left with Psychosis (Diagnosed as Schizophrenia; however it's drug induced psychosis really), and his motor/social skills are shot to pieces.
I somehow expect that this chap is to cannabis what an alcoholic is to booze: both extreme cases.
The bottom line, however, is that NO 'recreational' drug is compatible with flying. That includes cannabis, alcohol (how many accidents in the past?) and caffeine and all the other nasties.
Incase you're wondering about caffeine, it's truly dreadful. Appalling for concentration-heavy tasks, like flying, is likely to cause heart arrythmia (Sp?), migraines, poor sleep levels and may contribute to an individual's high stress levels. Most surprisingly, in one study, it had a greater mental debilitating effect than ALL other 'recreational' drugs, including LSD! Anectodal evidence backs this up.
Not surprisingly, the only documented positive effect of caffeine is to reduce the effects of caffeine withdrawal! The true concentration wonder-drug would be nicotine, so we should all patch up before flight!!
I'll stop now before I start boring myself too!!!
