How Schizophrenia Impacts Cognitive Function

Schizophrenia is a disorder with readily observable symptoms including hallucinations, delusions, social withdrawal, apathy, and disorganized thinking and behavior. It is also associated with substantial cognitive deficits, which interfere dramatically with everyday functioning. Robert McCutcheon, Richard Keefe, and Philip McGuire recently published an excellent review in the journal Molecular Psychiatry that summarizes current knowledge about cognitive impairment in persons with schizophrenia.

Cognitive deficits associated with schizophrenia include difficulties with attention, working memory, learning, and processing speed. These deficits interfere with real-world functioning. They are associated with increased hospitalization, longer hospital stays, and decreased compliance with treatment.

Cognitive impairment is also a major contributor to illness-related disability, defined as an inability to work productively and/or live independently. Psychiatric illnesses, including schizophrenia, are among the leading causes of disability across the human lifespan.

Although, in general, persons with schizophrenia perform poorly on cognitive tasks and average in the lowest 5 to 10 percent of the population when compared to those without schizophrenia, the degree of deficit varies greatly among individuals. It is possible that some individuals have cognitive deficits in one area while others have deficits in other cognitive domains. Sorting out various patterns of cognitive deficits among individuals will require further research.

Natural History

Cognitive deficits typically precede the onset of behavioral symptoms in individuals who eventually develop schizophrenia. These cognitive deficits are often present during childhood and increase during adolescence. This differs from the time course of cognitive changes in bipolar disorder where such changes occur largely after the onset of mood symptoms.

The cognitive deficits that develop during childhood in those with schizophrenia remain relatively stable through middle adulthood. As individuals become elderly, they are at higher risk for cognitive decline. However, such late-in-life deterioration might result from a variety of health factors that are common in individuals with schizophrenia and that contribute to premature death in these individuals.

Pathophysiology

Various brain circuits and neurotransmitters play a role in the development of cognitive deficits. Elucidating which neurotransmitter systems are involved in which brain systems will require much more research.

Treatment

It is well known that both older- and newer-generation antipsychotic drugs do not substantially alter the cognitive deficits associated with schizophrenia. Novel medications are being developed to treat schizophrenia, and increased attention is being directed toward developing drugs that help ameliorate cognitive deficits.

Knowing which specific cognitive deficits an individual with schizophrenia is experiencing can assist caregivers in tailoring psychosocial management. Neuropsychological testing can determine the type and degree of such deficits.

Advances in neuroscience will result in an improved understanding of the nature and causes of schizophrenia. This should lead to advances in novel drug development. Together with increased attention to psychosocial interventions, these advances should aid the development of integrated, personalized treatment approaches to improve the everyday functioning and life satisfaction of those suffering from this devastating psychiatric disorder.

This column was written by Eugene Rubin M.D., Ph.D., and Charles Zorumski M.D.