People with Schizophrenia suffer from hallucinations and delusions. These are the "positive" symptoms previously mentioned. Hallucinations are when a person hears, sees, tastes, smells, or feels something that isn't there, and they believe it's real to the point that they cannot tell the difference between the hallucination and reality. The film A Beautiful Mind does a fantastic job of demonstrating this, because after watching half of the film you then realize that none of it was real - or was it? For a while you still feel confused, and this is exactly how a person with Schizophrenia can feel when they're half way between being ill and getting better. It's a very confusing and traumatic time, not knowing who or what to believe. John Nash, played by Russell Crowe in the film, reaches a massive turning point in the management of his illness, when he realizes something that helps him distinguish between reality and fantasy.* Unfortunately, not every person with Schizophrenia will find a "touchstone" to help them gain insight in this way, and so unless management is possible through medication, it can be an ongoing problem to help them to realise that their hallucinations are not real, as with Mr Man as I will explain later.
Mr Mans hallucinations are auditory - he hears voices. I think maybe this is where some people get the belief that people with Schizophrenia have a split personality. Maybe they think that it is the "other half" of their personality that they hear "in their head"? I don't know. I can tell you that this is not true though. People with Schizophrenia do not have a split personality. As for hearing voices "in their head" - remember that the hallucinations are so real that they cannot be distinguished from reality. If Mr Man closed his eyes and a stranger (a voice that he doesn't recognise) spoke to him, he wouldn't be able to tell the difference between the stranger speaking and the "voices", because the voices seem so real that they sound like they are in the room with him. Studies actually show that when people suffer from auditory hallucinations the same part of the brain is stimulated as when a person speaks to them.**
Many people with Schizophrenia suffer from auditory hallucinations. Sometimes these can be command hallucinations - when the voices tell the sufferer what to do, or commentary - when the voices do a running commentary on what the person is doing, or persecutory - when the voices threaten the person. Obviously these can cause a lot of anxiety for the sufferer, and along with delusions can make a person behave completely out of character. Delusions are beliefs that are not real, such as believing that one is being persecuted. John Nash, as portrayed in the film, believed that he was a secret agent of some kind, although in reality he suffered other delusions too. Another person I know believed she was Satan, and my husband believed that he had been selected to work for a "company".
Maybe behaving out of character is another reason why people wrongly believe that people with Schizophrenia have a split personality. Contrary to popular belief though, the sufferer cannot "snap out of it" and become "themselves" again, or switch between the two. The cause of their strange behaviour, as already mentioned, is due to hallucinations or delusions or a combination of the two, often referred to as Psychosis, which does not stop suddenly. Rather, this is a condition that requires medication and patience, and can take a long time to recover from. Actually some people with Schizophrenia may never recover. Statistics vary, depending on the source, but I have read that after 10 years 25% of all Schizophrenia sufferers will recover completely, either with or without treatment, and live a normal life. 25% will gain much relief from their symptoms through medication, and live relatively independant lives, and another 25% will gain a measure of relief from their symptoms but will have difficulty in living a normal life. The remaining 25% will remain hospitalised, or commit suicide. One statistic that every source seems to agree on is that one in every hundred people has Schizophrenia - maybe more common than you thought.
Mr Man probably fits into the third category - he has gained a measure of relief from his medication in that he is not usually delusional anymore, but he still lives with the hallucinations, although they are not as bad as they once were, and struggles with the negative symptoms as mentioned previously. Another important milestone is that he now has insight into his illness - that is, he knows that he is ill and that he needs medication. When people with Schizophrenia are really ill, they don't know it. Typically they have a "lack of insight" into their illness. If you ever hear someone say "I think I might be Schizophrenic" it's very unlikely that they are. You can't think that you might be delusional, or think that you might be hallucinating. By their very nature, if you can come to the conclusion on your own that these are symptoms of an illness and not reality, then you can't be experiencing them. Even now, although Mr Man is not usually delusional, he still struggles to believe that the voices are not real.
I say he's not usually delusional, but high levels of stress can aggravate symptoms. It can be quite difficult to strike a balance when encouraging a person with Schizophrenia to push the boundaries, to try to overcome their anxieties, while at the same time being careful not to push them beyond what they can cope with and thus making their symptoms worse, or even causing a relapse. Another cause of relapse is if the person stops taking their medication, which is very common in people with Schizophrenia for various reasons. Probably the most common reason is that sufferers believe that they don't need their medication anymore once they are feeling better again, and of course as previously discussed they're not aware when their symptoms start returning. Another reason is the awful and often embarrassing side effects that they have to endure, including drooling, and twitching. In the past Mr Man has stopped taking his medication because the voices "told him to", and as I said he still hears them and struggles to believe that they're not real.
Another misconception is that people with Schizophrenia are violent. This is due largely to the fact that whenever a person with Schizophrenia does act violently in some way it is publicised in the news. Of course people without Schizophrenia commit violent acts every day. People with Schizophrenia are no more likely to harm others than anyone else. In fact they're more likely to harm themselves, with statistics showing that one in ten sufferers commit suicide.
*For the sake of helping the viewer to understand the nature of hallucinations and delusions John Nash is portrayed as a person who suffers from both auditory and visual hallucinations, which is not the case. According to Wikipedia his hallucinations were exclusively auditory, and John Nash hints towards this himself in an interview at Nobelprize.org. Bearing this in mind, I am unsure just what exactly his "touchstone" was, or if indeed there really was one. As mentioned previously, some people with Schizophrenia will recover completely in time anyway.
**Some people hear voices in their head, but that is a different problem with other causes which I know little or nothing about. These are called Pseudo hallucinations. This is when a person experiences something that is not there, but they can distinguish between that and reality. As an example, Mr Man used to see faces that appeared like holograms. Although he was convinced that they were there, he knew that these were not real people, hence it was not a true hallucination. I don't know what connection there is between this kind of hallucination and Schizophrenia, if any.