3 Theoretical models and psychological explanations of depression
The prevalence of depression was already well-recognised more than half a century ago. Indeed, Martin Seligman (1973-1975) is often cited for having referred to depression as the ‘common cold’ of psychiatry because of the rate at which it was encountered at the time. Our understanding of depression began to transform in the 1950s and 60s with the introduction of tricyclic ‘antidepressant’ medications, and psychological theories of depression that were mainly based around behaviourist, classical conditioning and psychodynamic theories, which evolved during this period. Theoretical models and psychological explanations for depression (see Box 8) progressively developed over subsequent decades.
Box 8 Psychological theories and models of depressiona
Behaviourist theory: classical conditioningb (associating stimuli with negative emotional states) and social learning theory (behaviour learned through observation, imitation and reinforcement).
Operant conditioning (Lewinsohn, 1974).
Psychodynamic theories (1960s-70s).
Beck’s (1967) cognitive model: cognitive triad, cognitive distortions, core irrational beliefs.
Seligman’s (1973-1975) ‘learned helplessness’ theory.
Abramson, Seligman and Teasdale’s (1978) ‘attribution’ model.
Abramson, Metalsky and Alloy’s (1989) ‘hopelessness theory of depression’.
Wolpe’s (1986) model of ‘neurotic depression’: depression secondary to ‘maladaptive anxiety’ through classical conditioningb; all non-psychotic problems can be reduced to specific fears.
Various models of rumination: the concept of depression as ‘overthinking’, e.g. Nolen-Hoeksema’s (1991) ‘Response Styles Theory’ of rumination (consisting of repetitively thinking about the causes, consequences, and symptoms of one's negative mood), or Conway et al's (2000) ‘Rumination on Sadness’ theory (seeing rumination as repetitive thinking about sadness, and circumstances related to one's sadness).
Note [a] A ‘theory’ can be considered to represent an ‘explanation’ or a ‘hypothesis’ that can be used to predict an event(s) or an observation(s), or to identify relationships or associations between concepts; theories can be inductive (a ‘bottom-up’ approach) or deductive (a ‘top-down approach’); a ‘psychological model’ can be thought of conceptually as a simplified representation of a theory, often presented in diagrammatic form, that allows theoretical predictions to be tested (providing evidence for or against a particular theory). Note also that a ‘biological model’ is used in relation to experimental research (e.g. to denote cellular, molecular, animal or clinical ‘models’). ‘Models’ used in this context can also be thought of as ‘evidence-based representations’ designed to test specific hypotheses.
Note [b] ‘classical conditioning’ is a learning process which occurs when two stimuli are repeatedly paired such that a response typically elicited by the second stimulus is eventually elicited solely by the first stimulus; ‘operant conditioning’ is a learning process in which the likelihood of a specific behaviour is modified (may increase or decrease) as a consequence of (or in response to) a reinforcing stimulus such as a punishment or a reward.
The diathesis-stress model, which is central to an understanding of depression, considers depression to be triggered by a combination of negative or stressful life event(s) (e.g. loss of an important source of love, security, identity or self-worth; death of a loved one, breakdown of a relationship or a significant personal failure) and vulnerability factor(s) (termed ‘diathesis’) that make the individual susceptible to depression. The theory was predicated on observations that depressive episodes are often preceded by negative life events. A depressive episode therefore tends to occur when a person who is vulnerable to depression experiences a negative life event, and this can be characterised by feelings of hopelessness and/or worthlessness, which may resolve quickly or turn into long-term depressive illness.
Self-referent thoughts, feelings and excessive rumination (negative introspection, self-reflection) are prominent features of depression and depressive episodes. A century ago, Sigmund Freud (1917) published his seminal work titled ‘Mourning and Melancholia’ in which he argued that depression can take two forms: ‘mourning’ the loss of a loved one characterised by intense sadness and despair, but not (typically) guilt, shame or self-reproach; and what he termed ‘melancholia’ characterised not only by intense sadness, but feelings of self-recrimination and self-deprecation, a failure of living up to one's ideals or standards. Contemporary views see ‘hopelessness’, ‘worthlessness’ and ‘helplessness’ as self-referent perceptions that are prominent features of depression. People can feel hopeless if they believe there is nothing that can be done to bring about a desired outcome or to avoid a negative outcome (develop feelings of resignation), they can feel worthless when they feel weak, inadequate or flawed, and they can feel helpless when they feel powerless to change an undesirable situation. These perceptions are interlinked, and prominent features of depression.