I believe there is a more general point to be made here. Namely, the effects of most (if not all) psychoactive substances don’t decay with their half-life. A more useful framing would be that they don’t track blood concentration all that well, and psychoactive effects can last both significantly longer or shorter than looking at the half-life would predict. I don’t do theoretical analyses such as yours, because I don’t expect getting much insight that is not available through (other people’s) empiricism.[1]
Consider a few cases: (half-life numbers found through quick googling)
Caffeine - [2] Looking at your applet, it suggests a ~fourth of (effective, after including paraxantine) the peak concentration after 16 hours. But at the same time, I would predict that taking a bolus caffeine dose after waking up would cause less sleep disturbance than taking a paraxantine dose in the evening to produce the same (effective) blood concentration. I presume you would expect this as well?
Phenibut—half life 5.3 hours. Psychonaut wiki lists the duration of effects as 10-16 hours which basically matches my experience. By any objective/subjective metric I’d predict we’d find the effects to dimish more slowly than with caffeine.
Armodafinil—half life 15 hours. Duration 8-15 hours, which, again, matches my experience. Note, the duration is a bit shorter than with phenibut despite the huge half-life difference.
Nicotine
Nicotine half life 1-2 hours. Duration (from buccal administration [3]which I use) 0.5-1.5 hours.
Psychedelics (in general) - I believe psychedelic trips are largely inexplicable through any exponential decay model (of psychoactive effects). I can explain, if you don’t share this intuition.
I could go on, of course. But my overall point is that regardless of whether one uses receptor affinity and occupancy and dowstream metabolites or more/other variables in one’s model, said model will likely still not be accurate enough to predict subjective effects.
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Though I heard about Paraxantine before
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Psychonaut wiki lists duration as 2-5 hours which is proably a bit too short, but not by much.
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Administration can also alter the duration of effects greatly. Way more than looking at plasma concentrations would predict.
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Presumably, there must be research on this?
I doubt this is caused by lack of clear thinking on the doctors’ part.
The process of identifying root causes you advocate is resource and time intensive. Sure, a determined patient, such as yourself, could go on the journey of finding some root cause, but this is not scaleable.
Consider, a man with insomnia goes to the doctor and hears:
”Instead of doing the foolish thing of stopping at diagnosing you with insomnia, I’ll to the wise thing. Could you tell me in detail about your lifestyle and family history? This interview could take several hours, we wouldn’t like to miss the root cause outside your body, after all. If this fails, I’ll order a vast array of medical tests, it will be expensive and take a while, no guarantees it’ll work. But we MIGHT identify some cause outside the body, wouldn’t that be grand.”
Physicians do this to a much smaller extent, when the expected value is especially positive. But giving the full treatment above for every patient, and for every not-fully explained health problem, would overwhelm the healthcare system and the benefits seem doubtful.
Additionally, the median patient is a constraint as well. You may want to have a doctor such as the one I described above, but I’d expect the median patient to not go along with this arduous and expensive process which may or may not lead to a solution at the end. Even if you identify some root problem in the patient’s lifestyle, this is unlikely to solve much. My understanding is that convincing patients to make even minor lifestyle changes is extremely hard, while convincing them to take pills is easier.