Évolution du concept d’apathie : nécessité d’une approche multifactorielle dans la schizophrénie

Abstract

Schizophrenia is a chronic and severe mental illness that affects over 1% of the population, characterized by multiple symptom dimensions. One of this class of symptoms, "negative symptoms", have received more attention over the last few years. Negative symptoms, including among others blunted affect, withdrawal or apathy, are particularly important for recovery and are associated with negative functional outcomes, such as inability to get an employment and conduct normal daily living activities. While positive symptoms are usually treated by antipsychotic drugs, negative symptoms are usually persistent, which indicates the need for better treatment. The aim of this article is to highlight recent scientific progress on apathy and to explore current multidimensional approaches of this concept in schizophrenia. Apathy is a symptom frequently encountered in schizophrenia and in many neurological disorders. Therefore, it can be regarded as a transnosographic symptom. A long time considered as a loss of motivation (psychological concept hard to define), recent descriptive and etiological models have proposed to consider apathy as a multidimensional phenomenon. Marin et al., have proposed a model of apathy in reference to the motivation concept. Marin et al.'s apathy model is composed of three dimensions: firstly, cognitive dimension, secondly, sensory-motor dimension and thirdly, affective dimension. These authors propose to differentiate "apathy syndrome" from "apathy symptom". "Apathy syndrome" resulting from a lack of motivation whereas "apathy symptom" results from cognitive and/or emotional/affective disorders. In addition, Marin et al. propose that apathy syndrome corresponds to the "lack of motivation" not attributable to diminished level of consciousness, cognitive impairment or emotional distress. Following this proposal, Levy and Dubois propose to define apathy as a quantitative reduction of self-generated, voluntary and purposeful behaviors. It is therefore observable and can be quantified. Levy and Dubois have proposed an apathy model considering: firstly, apathy as a syndrome related to reduction in goal-directed behaviors; secondly, anatomically, apathy can be secondary to dysfunctions or lesions of the prefrontal cortex. Since the prefrontal cortex is functionally and anatomically heterogeneous, subtypes of apathy occur in diseases affecting the basal ganglia, because these diseases disrupt associative and limbic pathways from/to the prefrontal cortex; thirdly, from a pathophysiological point of view, apathy may be explained by the impact of lesions or dysfunctions of the basal ganglia, because these lesions or dysfunctions lead to a loss of temporal and spatial focalization, both of which result in a diminished extraction of the relevant signal within the frontal cortex, thereby inhibiting the capacity of the frontal cortex to select, initiate, maintain and shift programs of action.