Figure 2.

Theoretical model of depression and antidepressant effects based on a connectionist inspired network. Blue arrows represent normal interactions between nodes. Red arrows represent pathological interactions. Antidepressant effects are indicated by green arrows. Increased weight/interaction between nodes is represented by bold arrows. Filled red nodes indicate a pathological change of state, while filled green nodes represent an antidepressant-induced reversal from a pathological state to a normal state. Core behavioural/cognitive traits relevant to the depression diagnostic (hedonic behaviour and mood) are indicated by plain nodes while dashed nodes represent secondary traits (stress coping or cognitive processing). Different colours of the output correspond to the state of the subject (green: normal, red; depressed, purple: comorbid pathology). (A) Normal state, (B) depressive episode induced by dys-regulation of a single end point leading to a core behavioural impairment (e.g. mood), (C) depressive disorder induced by dys-regulation of multiple end points leading to impairments in multiple psychological functions together mediating symptoms of depression, (D) comorbid pathological state induced by dys-regulation of a single secondary end point, (E) hypothetical effects of an antidepressant treatment in scenario 2B, (F) hypothetical effects of an antidepressant in scenario 2B, (G) hypothetical effects of a cognitive behavioural therapy or an emotional regulation therapy on a subject displaying profile 2C and (H) hypothetical view proposing that depression can be recapitulated by a crucial process, neuroplasticity.