The negative symptoms of schizophrenia are usually treatment-refractory, and considered to be a major cause of a poor outcome. Recently, it has become an important issue to elucidate the etiology of and develop treatment for negative symptoms in order to improve the outcome of schizophrenia patients.
 Firstly, the history of negative symptoms was reviewed. Several lines of factor-analysis studies have suggested that negative symptoms are independent from other symptoms of schizophrenia, and consist of two factors, the poverty of expression and avolition, while the results depend upon the assessment scale employed in each analysis.
 Anhedonia, a part of avolition, may be considered as the impairment of pleasure-seeking behavior, the impairment of remembering non-current feelings, and a person's belief that he/she cannot experience pleasure, rather than the loss of pleasure itself. As neurological bases for avolition, decreases in reward expectancy, value representation, and the behavior to seek uncertain reward were observed, which resulted in poor social functioning due to the difficulties of initiating adaptive behaviors for the future. These impairments are the bases of decreased intrinsic motivation. The negative symptoms were considered to result in poor social functioning mediated by neuro-and social cognitive dysfunction and dysfunctional cognition, such as low self-efficacy and self-stigma.
 Pharmacotherapy for negative symptoms remains to be established due to a lack of evidence. Several psycho-social interventions in self-efficacy, self-stigma, intrinsic motivation, and environmental contexts are now being developed, while their effects are rather limited. The principles of psychiatric rehabilitation, i. e., respecting one's own value system and preference, self-determination, and motivation, are worth revisiting from the viewpoint of neuro-cognitive science. Furthermore, a hope-oriented approach, the presence of peers, and reconstructing social values as barrier-free may be considered to be of marked help not only for treating negative symptoms through re-establishing self-esteem, but also to aid the general population.
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