Type I and Type II
Some systems for classifying different types of schizophrenia are not recognized by the American Psychiatric Association (APA) and so do not appear in the Diagnostic and Statistical Manual. One that you may come across is the Type I and Type II classification.
This system for describing subtypes of schizophrenia can be found in some psychology textbooks, research papers, or certain websites. It may be used because some people are dissatisfied with the usefulness of the DSM-IV classifications, which critics claim do not provide adequate indication of a patient's chances of recovery or the course her disease is likely to take. The DSM-IV classifications, some people say, are more descriptive than clinically useful. The APA's system also largely ignores overlap of symptoms in some people. The Type I/Type II classification approach emphasizes the relative predominance of positive and negative symptoms in a particular patient.
Type I Schizophrenia
Patients with lots of hallucinations, delusions, and/or disorganized or bizarre behavior — that is, positive symptoms — are included in the Type I category. People in this subset often functioned fairly well before becoming ill. They tend to develop schizophrenia later than Type II patients and generally experience a faster onset of disease.
Disease symptoms tend to wax and wane for patients with Type I disease; troubling episodes are interspersed with remissions. Patients function normally in society during remissions. They have a better chance of recovery even though they are more likely to be diagnosed with one of the classical subtypes of schizophrenia: paranoid, undifferentiated, catatonic, disorganized, or residual. Their cognitive or intellectual abilities are more likely to be only minimally impaired compared to people with Type II schizophrenia.
The biological basis of Type I schizophrenia is assumed to involve significant biochemical abnormalities as well as less detectable — perhaps more subtle or even minimal — structural brain abnormalities. The underlying biochemical flaw may be related to too much dopamine activity in a network of sites in the brain called the limbic system, which is closely associated with emotion. Proponents of this classification system say this is consistent with the greater effectiveness of typical or older antipsychotic medication in Type I patients.
Type II Schizophrenia
Patients with Type II disease show more negative symptoms than do Type I patients. Their faces are unexpressive. They lack initiative and motivation, don't pay attention, are withdrawn, can't find pleasure in life, and don't talk much. When they do speak, it is in a monotone. Rather than being diagnosed with paranoid, disorganized, undifferentiated, catatonic, or residual schizophrenia, they are more likely to meet criteria for a type of schizophrenia dominated by negative symptoms.
Type II patients are more likely to be men than women and are more likely to have had problems functioning in school, at work, and in their social life before being diagnosed with schizophrenia. They also tend to develop the illness at an earlier age.
Type II patients generally experience a steadily worsening condition, which eventually causes undeniable impairment and dysfunction so severe it couldn't be explained as eccentricity or disinterest in social interactions. It is harder for people with Type II schizophrenia to regain the level of functioning they had before the illness was diagnosed. Disease symptoms tend to be chronic; they don't come and go as they do with Type I.
The biological basis of Type II schizophrenia has been hypothesized to involve too little dopamine activity in the frontal cortex, a part of the brain that plays an important role in intellectual functioning. This would be consistent with observations that cognitive problems are significantly worse in Type II schizophrenia than in Type I. As a consequence, social functioning in all areas of life is likely to suffer.
Other factors that might someday be included in alternative descriptions of schizophrenia subtypes include the likely course of the illness and the likelihood of schizophrenia being present alongside other psychotic and personality disorders. These factors are not well understood and therefore not well described in current descriptions of the disease.