The history of schizophrenia is still controversial. However, the recent history of the condition is well documented. In the nineteenth century, physicians began to describe an insanity that affected the young. In the early twentieth century, the term schizophrenia (a Greek derivation, literally meaning "splitting of the mind") was used to describe this group of patients. This word was used because it was thought that the cause of schizophrenia was due to a disconnection between emotion, thought, and behavior. Although the term is still used today, the diagnosis is now based on the symptoms and the course of the illness.

A simple way to understand the symptoms of schizophrenia is to think of them as positive or negative. A positive symptom is one that is added. The positive symptoms are hallucinations, delusions, and disorganized speech and behavior, which are collectively referred to as "psychosis." Hallucinations are disturbances in the five senses (sound, sight, touch, smell, and taste). A common hallucination noted in schizophrenia is the hearing of voices. These voices vary in character, ranging from simple commands to intricate conversations. These voices are not a misinterpretation of sounds or talking. They come from inside the patient. Another common positive symptom is delusional thinking. A delusion is a fixed, false belief. It is fixed, because the patient will not change his or her view in the face of reason or contradictory evidence. An example of delusional thinking, then, might be a patient thinking that the CIA has secretly implanted a computer chip in his or her brain. Although the delusional patient can have a head x-ray or magnetic resonance imaging (MRI) that would prove that there is no chip, he would continue to insist and react to the notion that a chip is implanted, and that the head imaging must have been wrong, or even that the chip might have been invisible to MRI detection. Another common positive symptom seen is that of disorganized speech. Disorganized speech is characterized by strings of words expressing ideas that have no obvious connection; for example, "Doctor, I went to bed at ten because I have a pen, she doesn't care about the rock, I need to do pushups, Hi Doc." Also, a patient's speech is often accentuated by long pauses, which might be a clue to something called "thought blocking." This postulates that the patient's normal train of thought is being interrupted, that is, "blocked," by some internal process, for example, voices.

In contrast to a positive symptom, a negative symptom is one that is missing from normalcy. These symptoms include apathy (lack of emotional expression) and greatly decreased motivation. Patients with schizophrenia do not show the normal range of emotions. They have minimal facial expressions, and their emotions seem blunted. Also, their motivation is diminished and they do not adhere to goals, even though they may have been very goal-oriented in the past. The lack of motivation can cause patients to neglect basic personal hygiene. These negative symptoms contribute to the social withdrawal that characterizes schizophrenia, and consequently are considered a destructive part of the illness that leads to a poor quality of life for the patient.

Classically, schizophrenia develops slowly and may not be immediately recognizable to the patient and family members as an illness. Patients in the first stages of schizophrenia may become withdrawn, seem aimless, and display subtle oddities. An example might be an individual preoccupied with nuclear disarmament, yet not making progress in trying to learn about and participate in solving the problem. These "soft" signs may not cause concern to family members. However in schizophrenia this period is followed, roughly about five years later, by a florid presentation of positive symptoms. The positive symptoms, which may erupt suddenly, usually present in males in the early twenties and in women a few years later. The ages of presentations vary, however, and children or even older people may develop schizophrenia.

The next stage of schizophrenia is generally characterized by a decrease in the positive symptoms, while the negative symptoms continue. Roughly one-half of patients who survive to old age can function well in society and are not in need of custodial care, for example, hospitals or community institutions; and some of these patients recover completely. Unfortunately, the number of patients who recover is less than what it could be. Sadly, the rate of suicide is extremely high (approximately ten percent) in schizophrenia. Furthermore, patients with schizophrenia tend to die prematurely from other medical conditions. This might be secondary to poor access to medical care, possible unhealthy lifestyles, or inherent predispositions to various physical illnesses. What is known is that many patients with schizophrenia do not live long enough to enjoy the abatement of their worst symptoms.

Approximately one percent of the world's population will develop schizophrenia, and males and females are affected at the same rate. Schizophrenia afflicts individuals throughout the socioeconomic spectrum, but due to the symptoms of the illness and its chronic course, most patients with schizophrenia drift down to the lower socioeconomic groups.