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Though a major illness in modern society, depression is still not completely understood. A number of empirical observations point to the importance of basic cognitive processes as well as personality variables as antecedents of a depressive disorder. In this work it is argued that “state orientation”, a personality style characterized by the inability to actively influence one’s focus of thought, plays an important role in the development of at least some forms of major depressive disorder. In the present work, it is suggested that (1) state-oriented cognitions are equivalent to sustained information processing, that (2) depressed individuals are characterized in particular by state-oriented cognitions related to prior failure experiences, that (3) sustained processing of affective information will interfere with normal executive cognitive functioning in depressed individuals resulting in impairments of normal behavior, and that (4) both sustained information processing and “affective interference” will be associated with specific dysfunctional patterns of brain activity in depressed individuals. In the first chapter of this thesis, theorizing pertaining to “action control” and the relationship between action control and state orientation are reviewed. After having established the potential functional significance of state-oriented cognitions, their possible link to depression is developed by introducing the “degenerated-intention hypothesis”. Afterwards, the role of state orientation in the advent of the depressive state is discussed against the background of the “functional helplessness” model of depression. Next, recent empirical findings related to executive dysfunction associated with state-oriented cognitions in major depressive disorder and related dysfunctional patterns of brain activity are reviewed. By considering evidence from studies on executive functioning, brain imaging, and neurophysiological studies, support is found for a possible frontocingulate dysfunction associated with a state-oriented cognitive style underlying a major depressive disorder. Consistent with the proposed link between depression and state orientation, in the second chapter of the thesis, Studies 1a – 1c demonstrate that subclinically and clinically depressed individuals are specifically characterized by failure-related state orientation. Moreover, the results of Study 2, described in Chapter 3, reveal that sustained processing of affectively valenced information may indeed interfere with subsequent executive cognitive functioning, especially in individuals demonstrating relatively high levels of depression. Finally, in line with the idea that sustained information processing and affective interference will be related to an individual’s level of state orientation and will be reflected in specific patterns of neural activity, Study 3, presented in Chapter 4, provides considerable evidence for disturbed brain function in clinically depressed individuals during processing of affective information as well as subsequent executive cognitive functioning and its relation to state-oriented thought. The current research supports the idea that state orientation, in particular its failure-focused form, is a crucial process involved in the development and maintenance of a depressive disorder. Specifically, the present findings suggest that certain forms of major depressive disorder are associated with sustained processing of affective information and with the resulting affective interference with executive cognitive functioning. Findings further suggest that sustained information processing is experienced by affected individuals as ruminative, state-oriented thought on past aversive experiences, and that both sustained information processing and affective interference are associated with distinct patterns of brain activity, which are related to early stimulus evaluation, conflict monitoring, and conflict resolution. The processes possibly underlying some forms of depression, as proposed in this thesis, comprise what may be called “the spinning mind”, whose important functional significance is to hinder an individual from adaptive behavior by impairing the ability to direct thought. Although state orientation may therefore appear to be maladaptive per se, it may be argued instead that this mode of action control is also an adaptive process as long as critical limits of certain parameters are met and the spinning mind is prevented. These and similar considerations are addressed in the concluding discussion in Chapter 5.