Cognitive reserve in neuropsychiatry

Background. The idea that superior cognitive function acts as a protective factor against dementia and the consequences of head injury is well established. Here we suggest the hypothesis that cognitive reserve is also important in neuropsychiatric disorders including schizophrenia, bipolar disorder and depression. Method. We review the history of passive and active models of reserve, and apply the concept to neuropsychiatric disorders. Schizophrenia is used as an exemplar because the effects of premorbid IQ and cognitive function in this disorder have been extensively studied. Results. Cognitive reserve may impact on neuropsychiatric disorders in three ways: by affecting the risk for developing the disorder, in the expression of symptoms within disorders, and in patients' functional outcome. Cognitive failure below a certain threshold may alone, or in combination with common psychiatric symptoms, produce neuropsychiatric syndromes. Conclusions. Consideration of cognitive reserve may considerably improve our understanding of individual differences in the causes and consequences of neuropsychiatric disorders. For these reasons, the concept of cognitive reserve should be incorporated in future studies of neuropsychiatric disorder. It may be possible to enhance cognitive reserve through pharmacological or non-pharmacological means, such as education, neurocognitive activation or other treatment programmes.