The reason I headcanon Bell with persecutory paranoia is because of LSD and its derivatives. Considering what the CIA was like at that time and that Bell was unwittingly part of MK Ultra, it's easy to think that the drug Adler administered to him was LSD.
(Original draft in Spanish)
At that time, the CIA used LSD in their interrogations, sometimes even in interviews, calling it "truth serum". The reason behind this was that by administering LSD, they could keep the subject's fear at very high levels for hours. Besides the drug, they also planted ideas in their heads, such as the Soviets being after them, that if they didn't do what was asked they would be handed over to the Soviets, and that the Soviets weren't as "friendly" as they were. But as you can see, just one of the many things the CIA did.
Taking all of this into account, it is most likely that Bell was given a drug similar to LSD, or LSD itself, to keep him docile, confused, frightened, and willing to do anything for them. Another possible substance, which I believe is the most accurate of all, could have been 3-quinuclidinyl benzylate (US Army code EA-2277, NATO code BZ, Soviet code Substance 78); a chemical weapon. This substance can be given through the eyes (affects the different membranes that are part of the eyes) or mouth, and the duration of its effects is even longer than that of LSD, lasting up to 3 days. One of its effects, apart from very strong hallucinations, almost indistinguishable from reality, and dissociation, is memory loss. This actually fits better with the kind of things I believe Bell suffered when he was captured by the Americans. Other effects, depending on the amount and moderation, are: anticholinergic toxic syndrome, disorientation, ataxia, asthenia, loss of consciousness or the ability to breathe, arrhythmia and coma.
3-quinuclidinyl benzylate was one of the drugs administered to the more than 7,000 soldiers who "volunteered" to test 250 different substances in the United States.
This substance is not inherently deadly, but like LSD and other drugs such as phencyclidine (PCP), it can increase the risk of suicide.
When someone suffers from paranoia, they cannot think clearly and are much more susceptible to all kinds of stimuli. Anything, no matter how trivial it may seem, could be interpreted as a sign of being watched, followed or something similar. It is not a pleasant feeling to be in a constant state of alert due to the terror one can experience.
After all, one of the main objectives of MK Ultra was to incapacitate and manipulate/influence.
