Conveying Schizophrenia

Alright, again I have to start off by explaining how /careful/ you have to be when roleplaying such a mental affliction. Honestly I can't think of anything worse than insulting someone who is friends/family of or has the condition.

It is a chronic, incredibly severe and disabling disorder, that has affected people all throughout history. It can terrify people with the illness, and cause them to become very withdrawn. People with the condition can have trouble keeping a job or caring for themselves, and as such are often seen relying on others. Yes it is possible people with the condition might assume others are reading their minds, controlling their thoughts or planning to harm them in some way.

Schizophrenia is largely an inability to distinguish reality from fantasy. Often they can hear voices in their heads, or see things that aren't even there. They can come across as delusional, and misinterpret real events that have happened, to fit their own fantasies, potentially drawing great conspiracies from a simple hand shake and coy smile.

Potential conditions of schizophrenia are 'genes' and environment. It's commonly known that schizophrenia runs in families. Or more that it has a higher chance of affecting those who have a parent or relative that have the disorder. Imbalances in brain chemicals are also probable causes, as are exposure to viruses at birth, along with malnutrition and other complications during birth.

Someone with schizophrenia must battle tremendously to lead a normal life and earn a living. They can have great emotional distress on a daily basis. If someone expresses concern with your representation of this condition, then you /must/ re-evaluate your character.

Symptoms:

• Hallucinations
• Generally those affected are able to see, hear, smell or feel something that no one around them realistically can sense. Typically the most common of these are hallucinations. People with the disorder hear voices, and these voices can talk about their behaviour, order them to do things, or warn them of 'danger'. Sometimes these voices can talk to one another? Other examples of hallucinations would be seeing people or objects that aren't actually there. Or smelling smells that don't exist.
• Delusions
• False beliefs that aren't part of their culture/race. They can believe these beliefs/delusions even after they are proved not to be logical. Often this symptom causes the individual to come across as bizarre, and could be as far fetched as a neighbour controlling their every action with magic. They might even believe themselves to be someone completely different to who they are, for example a famous politician. 
• Thought disorders
• Unusual or dysfunctional ways of thinking, but still ultimately different to delusions. A format of this symptom is 'disorganized thinking'. Having trouble organizing thoughts or concentration, or even connecting the thoughts logically. They might talk in a disconnected manner that is difficult to piece together. Other than this, they might stop abruptly in the middle of talking or thinking. When asked why, they could potentially comment that the thought had simply been taken from their mind. They may construct pointless neologisms.
• Movement disorders
• They may appear as agitated body movements. Fidgeting, paranoid actions, or actions repeated over and over and over again. The flip side is also possible. The individual may become periodically catatonic. Something that is considered much rarer. The individual would not move or respond to others.
• Positive symptoms
• Losing touch with reality. This feeling can come and go. Potentially being unnoticeable or alternatively incredibly severe.
• Negative symptoms
• Lack of pleasure in everyday life.
• Lack of ability to stick to planned activities.
• Little social interactions.
• Dull or monotonous behaviour. A flat blank face when talking to people.
• Cognitive symptoms
• Subtle symptoms that might be difficult to recognize as part of the condition.
• Poor ability to understand information and make decisions on it.
• Trouble focusing/paying attention.
• Problems with using information after learning it immediately.
• Addiction to substances

Treatment: 

• Whilst in a modern day real life setting, we are capable of treating those with such an affliction, it is generally assumed there is no cure in a more medieval setting. Any attempt at curing could potentially worsen the effects and the paranoia felt by the individual.

References:
http://www.nimh.nih.gov/health/topics/schizophrenia/index.shtml