Decreased serum BDNF levels in chronic institutionalized schizophrenia on long-term treatment with typical and atypical antipsychotics

State of Art of Serum Brain-Derived Neurotrophic Factor in Schizophrenia

“…Most of the studies (12/16) measuring serum BDNF documented lower concentrations of this neurothropin in patients with schizophrenia (Carlino et al, 2011;Chen et al, 2009;Grillo et al, 2007;Ikeda et al, 2008;Jindal et al, 2010;Jockers-Schrübl et al, 2004;Pirildar et al, 2004;Rizos et al, 2008;Tan et al, 2005a;Toyooka et al, 2002;Xiu et al, 2009;Zhang et al, 2008); however, in other studies, BDNF concentrations were either increased (Gama et al, 2007;Reis et al, 2008); or normal (Huang et al, 2006;Shimizu et al, 2003) (Table 1). Five out of the 16 researches investigated gender effects, demonstrating either significantly lower or higher serum BDNF levels in males suffering from schizophrenia (Gama et al, 2007).…”

“…In a second step, phase of illness and use of antipsychotic drugs were considered. We found that four studies enrolled only drug-naïve first-episode patients Jindal et al, 2010;Jockers-Schrübl et al, 2004;Rizos et al, 2008), eight studies recruited only chronic, medicated patients (Carlino et al, 2011;Gama et al, 2007;Ikeda et al, 2008;Reis et al, 2008;Tan et al, 2005a;Toyooka et al, 2002;Xiu et al, 2009;Zhang et al, 2008) and two studies included medicated patients with unclear phase of illness (Grillo et al, 2007;Huang et al, 2006). Notably, the study by Pirildar et al (2004) and Shimizu et al (2003) investigated both chronically antipsychotic-treated and drug-naïve patients; in particular, in Pirildar et al (2004) some first episode medicated subjects were included.…”

“…Drug-naïve schizophrenic patients without cannabis consumption showed similar results to normal controls and cannabis controls without schizophrenia. In relation to the source of recruitment, 6/16 studies included only inpatients Reis et al, 2008;Rizos et al, 2008;Tan et al, 2005a;Xiu et al, 2009;Zhang et al, 2008), 1/16 included only outpatients (Gama et al, 2007), 3/16 considered both in-patients and out-patients (Carlino et al, 2011;Huang et al, 2006;Ikeda et al, 2008) and 6/16 publications did not provide data (Grillo et al, 2007;Jindal et al, 2010;Jockers-Schrübl et al, 2004;Pirildar et al, 2004;Shimizu et al, 2003;Toyooka et al, 2002). In our research, we found that Japanese subjects were investigated in three studies (Ikeda et al, 2008;Shimizu et al, 2003;Toyooka et al, 2002), Caucasians in another four studies (Carlino et al, 2011;JockersSchrübl et al, 2004;Pirildar et al, 2004, Rizos et al, 2008 and Asians in five studies Huang et al, 2006;Tan et al, 2005a, Zhang et al, 2008.…”

“…Six studies reported no diagnostic subtypes of schizophrenia (Ikeda et al, 2008;Gama et al, 2007;Jockers-Schrübl et al, 2004;Pirildar et al, 2004;Reis et al, 2008;Rizos et al, 2008;Toyooka et al, 2002) while in seven studies it was assessed the differences in serum BDNF levels among diagnostic subtypes Grillo et al, 2007;Huang et al, 2006;Shimizu et al, 2003;Tan et al, 2005a;Xiu et al, 2009;Zhang et al, 2008). Different forms of schizophrenia had no association with BDNF serum levels in 5 papers (Grillo et al, 2007, Shimizu et al, 2003Tan et al, 2005a;Xiu et al, 2009;Zhang et al, 2008), while Chen et al (2009) showed significantly higher BDNF levels in paranoid (10.4 ± 4.3 ng/ml) compared to undifferentiated (8.0 ± 3.9 ng/ml) and other combined subtypes (7.5± 4.1 ng/ml). Huang et al (2006) showed that patients with catatonic schizophrenia had lower serum BDNF protein levels than patients with paranoid schizophrenia and residual schizophrenia.…”

“…To assess if BDNF can represent a good biomarker in schizophrenia, a growing number of studies compared BDNF serum levels between patients with schizophrenia and healthy control subjects but unfortunately, with controversial results. Indeed, several investigators found a significant decrease in serum BDNF concentrations (Carlino et al, 2011;Chen et al, 2009;Grillo et al, 2007;Ikeda et al, 2008, Jindal et al, 2010Pirildar et al, 2004;Rizos et al, 2008;Shimizu et al, 2002;Tan et al, 2005aTan et al, , 2005bToyooka et al, 2002;Xiu et al, 2009;Zhang et al, 2007Zhang et al, , 2008; while other studies documented normal (Shimizu et al, 2003;JockersSchrubl et al 2004;Huang et al 2006) or even increased circulating BDNF (Gama et al, 2007;Reis et al, 2008). Because of these discrepancies, we decided to perform a systematic review and a meta-analysis of studies measuring serum concentrations of BDNF to elucidate whether or not this neurotrophin is abnormally produced in patients with schizophrenia.…”