Major Depressive Disorder - Behavioral and Cognitive Perspectives and a Review of Cbt

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Major depressive disorder (MDD) is a mood disorder characterised by the presence of at least one major depressive episode in the absence of manic episodes and other disorders that may better account for presenting symptoms (e.g. schizoaffective disorder). A major depressive episode is defined as the presence of at least five of the following symptoms; depressed mood, loss of interest or pleasure, significant weight loss or gain, insomnia or hypersomnia, psychomotor agitation or retardation, fatigue, feelings of worthlessness or inappropriate guilt, lack of concentration or indecisiveness, and recurrent thoughts of death. To qualify as a major depressive episode, the five presenting symptoms must contain either depressed mood or loss of interest, persist for a two week period, and represent a change from previous functioning. Diagnosis of MDD includes description of the recurrence and severity (mild, moderate, severe) of episodes, and may be further characterised by features including chronic status, melancholy, and catatonia. The lifetime risk for MDD has been placed between 10-25% for women and 5-12% for men. Death by suicide is estimated at 15% for sufferers of severe MDD (DSM-IV-TR, American Psychiatric Association, 2000).

Theoretical conceptions of the development and maintenance of MDD stem from both the behavioural (e.g. Ferster, 1973; Jacobson, Martell, & Dimidjian, 2001; Lewinsohn & Libet, 1972) and cognitive (e.g. Beck, 1967) paradigms. In this report the core principles of each paradigm will be reviewed, followed by an exploration of specific depression models proposed by key researchers from each position. In addition to this exploration, the application of the cognitive model as a cognitive behavioural therapy (CBT) will be outlined. Finally, relevant literature regarding the effectiveness of CBT for MDD will be reviewed. This review will analyse the efficacy of CBT strategies in comparison to alternate MDD therapies, culminating in conclusions regarding the current status of CBT treatments for MDD.

Strict behaviourism suggests that as the inner workings of the human mind (i.e. cognitions) are not observable, scientific psychology should be rooted solely in the study of behaviour (Martin, Carlson, & Buskist, 2007). In the simplest sense, behaviourist learning theories suggest that behaviours which produce favourable outcomes will be repeated (and may become habits), while behaviours that produce unfavourable outcomes are less likely to be repeated (Ouellette & Wood, 1998). This core principle provides the bedrock for the behavioral perspective of all learning. Skinner (1953) elaborated upon this basic principle, proposing the theory of operant conditioning as the basis for the relationship between human behaviour and the environment. Operant conditioning suggests a three-term contingency, where discriminative stimuli precipitate behaviour (a response), which in turn leads to consequences. By manipulating relations among the contingencies in controlled animal studies, Skinner found behaviours were more likely to occur if they were positively or negatively reinforced, or less likely to occur if they elicited aversive (punishment) or no (extinction) consequences (for a review, see Martin, Carlson, & Buskist, 2007). While further elaboration of the operant framework (e.g. social learning theory, Bandura, 1969) expanded the understanding of human learning, structured behavioural analysis and its application to human problem solving can be attributed to the pioneering work of Skinner (Mazur, 1994).

Specific behavioural conceptions of ‘depression’ have been formulated within the operant framework. Collectively these conceptions focus on absent behaviours, or ‘inactivity’, as the chief protagonist in the emergence and maintenance of depression (Ferster, 1973; Jacobson, Martell, & Dimidjian, 2001; Lewinsohn & Libet, 1972). Lewinsohn and Libert (1972) suggest decreases in pleasant events, or increases in aversive...
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