Pathways to motivational impairments in psychopathology: Common versus unique elements across domains

Our ability as humans to engage in goal-directed actions that allow us to obtain outcomes that we desire is a core component of life satisfaction and achievement. Sadly, many forms of mental illness involve impairments in varying facets of motivation that are important contributors to the all too frequent impaired life function and reduced quality of life experienced by such individuals. As such, both the field of psychopathology research broadly and the Research Domain Criteria (RDoC) initiative have recognized the centrality of examining motivation and incentive processing in psychopathology. This review will focus on the types of motivational impairments seen in disorders such as depression and schizophrenia. Some individuals with depression do not engage in occupational, educational, or social behaviors that they might participate in when not depressed and may spend much of their time alone and engaged in very passive activities (sleeping, watching TV, etc.). Similarly, in schizophrenia, motivational impairments can also take the form of reduced efforts to engage in occupational, educational, or social experiences. In this review, we argue that elements of the final common pathway to impairments in motivation in depression and schizophrenia may be shared and are likely to involve deficits in what can be referred to as effort-cost decision-making (ECDM). This hypothesis suggests that a proximal cause of reduced engagement in occupational, educational, and social pursuits in both depression and schizophrenia is a reduced willingness to exert effort to obtain potentially rewarding or positive outcomes. However, we also argue that these ECDM deficits in depression and schizophrenia reflect differing distal mechanisms. More specifically, we argue that ECDM impairments in depression may be strongly related to reductions in hedonic experience of reward and pleasure, while ECDM deficits in schizophrenia may more strongly reflect difficulties with cognitive control and internal representation of future or past events and use of incentive information that is not currently available in the environment.