BDNF and bipolar disorder: Unfortunately, chronic GSK-3β inhibition with lithium ions, which are used in therapy against bipolar disorder, appears not to have the predicted protective effect against AD (Bauer et al.2003; Chuang 2004; Manji et al.1999), although it had been shown to regulate endogenous BDNF and NGF levels (Frey et al.2006a, b).