Why did he stop taking his meds? It seems to be a really common thing with schizophrenics.
Using a specific, clinical definition of addiction, it is fair to say that addictive drugs are precisely those that trigger the release of dopamine. Nicotine, cocaine, opioids, barbituates, amphetamines, diazepine, alcohol, and all pharmacologically related compounds are addictive. Drugs which don't affect the dopamine system aren't addictive in nearly the same sense: cannabis, THC and most hallucinogens, MDMA, and many others, for instance.
Antipsychotic drugs are basically the polar opposite of addictive drugs. Most all of them are dopamine antagonists, meaning they suppress dopamine function. As you might expect, this makes them singularly unpleasant.
Behaviorism is a branch of psychology that considers only the overall pattern of responses of humans/animals. It might seem like an extreme way to characterize humans, but I justify it (to myself at least) thus: Behaviorism does not describe individual choices, but it does describe the overall pattern of choices an individual will make. And it works exceedingly well - we can calculate, with surprising accuracy, what virtually any small group of individuals (and to a lesser extent, even particular individuals) will do in a given situation. It works for rats in cages pressing levers for food rewards, and also for predicting property crime based on the price and purity of meth or heroin. (As an aside, enforcement efforts that increase the price of the drug have the effect of dramatically increasing the total profits of drug suppliers and also the amount of property crime that occurs when addicts try to support their habit...)
Antipsychotics also affect this behavioral-reward pathway, but in the opposite direction. Even when patients rationally understand that the medicine is what keeps them together and that they're worse off without it, that behavioral drive seems to kick in eventually. The experience is perhaps analogous to continually quitting smoking. And it's not just patients with schizophrenia - the self-same drugs are commonly used in bipolar disorder (called "mood stabilizers") and epilepsy or other seizure disorders (called antimimetics or antiepileptics), and regardless of the disorder there are similar problems with compliance.
