BDNF and depressive symptom measurement: At the same time, it also cannot be ruled out that in the context of the overall low BDNF reserves commonly reported in depression [47,48,49], positive correlations between PPP-BDNF and pro-inflammatory indices might derive from a condition of allostasis overload in subgroups of MD patients displaying altered/blunted counter-responses during inflammation, such as the release of BDNF.