While amphetamines are dangerous, I would think that somebody who is getting very little sleep and eating very little/has a low blood sugar would be at a higher risk of health problems (including psychosis) than somebody on low-moderate doses of dextroamphetamine.
Is this to say amps are healthy? No. I'm just trying to show that the classic amphetamine addict "look" would not occur if they were eating and sleeping.
Amphetamine psychosis is only encouraged by not sleeping.
It's really hard to say how much each factor contributes, so I'm not even going to attempt to, and not being on amphetamines is always healthier than being on amphetamines.
Cannabis is probably the healthiest stimulant there is. I also find Cannabis to help me focus, and there are other reports of Cannabis helping people with this sort of thing.
I would highly recommend Cannabis over stims.
To be honest with you man, targetting any of the neurotransmitters (DA, NE, SERT) "is a bit like changing the oil in your engine by pouring oil all over the engine block. Some of it will dribble into the right place, but a lot of it will do more harm than good." (paraphrased from
this video you should watch)
To reiterate, I high recommend Cannabis over stimulants for you.
I am not a doctor, but it's pretty obvious to me which is healthier (and no it's got nothing to do with Cannabis being "natural")