mental illness
So we're Brian's issues caused by years of drug abuse, or was it organic? I know he had the panic attack on the plane , before he started using drugs, but this happens to a lot of people on airplanes, from time to time.
shareI think it was probably both. He used LSD for some time, pretty regularly and it's been known to cause long term psychosis in people who took acid on a regular basis over long periods of time. He also had suffered abuse and had anxiety related disorders so I think the drugs did nothing to help.
The movie doesn't really get into the "correct diagnosis" but if he was under the wrong medication, it could have prolonged the deeper effects of the psychosis he suffered.
For every lie I unlearn I learn something new - Ani Difranco
I think it was mainly the large amounts of amphetamines (not shown in the film) that caused a huge strain on his mind. He and Van Dyke, to some extent, used to take uppers to be able to work longer and then downers to be able to relax. It's like a magnet trying to pull a chunk of metal in different directions.
LSD may have shown him some painful truths about his life (indeed so overwhelming and difficult to deal with that it ultimately left him with voices in his head) but you don't get sick from psychedelics. They merely have the chance of enhancing a problem that was already there. Marijuana has been shown to be quite helpful to schizophrenics and alike, so I don't think that's the culprit.
Of course, he was somewhat coherent and active until Landy startes giving him his infamous "legal" drug cocktail. That's when Brian turned into more of what he is today, slurred speech and all.
Bottom line, the reason is probably that Brian has always been very sensitive and people like his father and Mike Love, among others, didn't really take that into consideration.
It seemed like his psychotic symptoms started before he had taken many drugs. If anybody is aware of the diathesis-stress model of mental illness, it states that life stressors can make the emergence of mental illness more likely, depending on your baseline risk. That might have been the influence of the abuse by his father. Apparently his correct diagnosis is schizoaffective disorder. This is sort of like having severe depression and schizophrenia, not always simultaneously. It can be very devastating.
shareYes schizoaffective disorder is correct. Brian's state is, more or less, serious mood swings aswell as a slight difficulty keeping his inner world separated from the external world, hence the voices.
Brian losing his grip on reality, or whatever you wanna call it, would also probably have happened without the drugs, at another emotionally overwhelming period (Maybe when his father died, maybe even when he was defeated by Smile). He surely benefited from his drug use, specifically LSD and marijuana, but in the end he probably took it in excess and it blew his mind, as the man himself would say. A time of strain within the band and pressure from all directions might not be the best time to trip too much. Too much on his hands already.