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Abstract:
It has been postulated that schizophrenia (SZ) is related to a lower
expression of brain-derived neurotrophic factor (BDNF). In the past few
years, an increasing number of divergent clinical studies assessing BDNF
in serum and plasma have been published. It is now possible to verify
the relationship between BDNF levels and severity of symptoms in SZ as
well as the effects of antipsychotic drugs on BDNF using meta-analysis.
The aims of this study were to verify if peripheral BDNF is decreased in
SZ, whether its levels are correlated with positive and negative
symptomatology and if BDNF levels change after antipsychotic treatment.
This report consists of two distinct meta-analyses of peripheral BDNF in
SZ including a total of 41 studies and more than 7000 participants: (1)
peripheral BDNF levels in serum and plasma were moderately reduced in SZ
compared with controls. Notably, this decrease was accentuated with the
disease duration. However, the extent of peripheral BDNF level decrease
did not correlate with the severity of positive and negative symptoms.
(2) In plasma, but not serum, peripheral BDNF levels are consistently
increased after antipsychotic treatment irrespective of the patient's
response to medication. In conclusion, there is compelling evidence that
there are decreased levels of peripheral BDNF in SZ, in parallel to
previously described reduced cerebral BDNF expression. It remains
unclear whether these systemic changes are causally related to the
development of SZ or if they are merely a pathologic epiphenomenon.
