Schizophrenia is a disease that affects many areas of the brain, causing patients to suffer many problems in brain functions. Generally people see schizophrenia as an illness of hallucinations, delusions, and disorganized thought process, but the first two kinds of symptoms are often the focus of attention of patients and families because of their striking nature. The disease is also characterized by cognitive deficits, which are problems in thinking that - among other capacities - involves learning, memory, and concentration. These cognitive deficits can have a profound impact on a person's functioning at work and school, as well as in his or her personal life. One way to look at the cognitive impairments that occur with schizophrenia is to divide them between those that happen early in the course of the illness and those that arise when a patient has become clinically ill.
Early research has shown that those children who go on to develop schizophrenia have slight but measurably lower IQ scores than children who do not develop the disease. Cognitive problems that arise early in life can lead to problems acquiring skills at a normal developmental rate. Problems with cognition that happen during or after the onset of schizophrenia tend to be far more severe than those that happen before.
During the first episode of psychosis that occurs in schizophrenia, every sphere of cognition can be impaired. This includes problems with language, attention, memory, visual-spatial skills, and executive function. Individual people vary in the impact of schizophrenia in these spheres, but the two areas that are most likely to be affected are memory and executive function. Executive function refers to mental processes that are involved in planning, purposeful action, and the ability to self-monitor behavior. The timing of these impairments has not been fully understood. It is possible that problems with memory, concentration, and executive function occur up to three years before the frank symptoms of psychosis occur. I have worked with teenagers who have had problems with grades and school absences for years before psychotic symptoms of schizophrenia revealed themselves.
In people who have severe chronic illness, the level of cognitive impairment is still very much a topic of debate. The results of many studies argue against the notion that schizophrenia alone leads to progressive cognitive decline in the way that Alzheimer's dementia does. The majority of research suggests that the level of impairment that happens around the time of the first episode of psychosis is fairly stable throughout middle age.
Many patients with schizophrenia and their families that I have encountered have had serious, legitimate concerns about cognition. The disease usually shows itself in the late teens and early 20's when many people are in or considering advanced schooling. A future blog will discuss the impact that treatments have on cognitive function in people with schizophrenia.