Figure 4.

The neurotrophic hypothesis (a) and an alternative affective bias hypothesis (b), which illustrate the different relationship between behavioural symptoms of MDD and changes in brain morphology. The novel model proposed here reverses the relationship between neuroplasticity and brain atrophy, suggesting these occur because of the behavioural changes induced by negative affective biases. *See [89] for more detailed discussion of relevant signalling pathways. BDNF, brain-derived neurotrophic factor.