NTRK1 and major depressive disorder: The changes of TrkB-FL mRNA and TrkB-T1 mRNA in peripheral blood mononuclear cells revealed to be a good predictor of depression after exercise intervention for METH addicts, while correlations were not found between SDS and TrkA mRNA, TrkC mRNA, and P75NTR mRNA (r = −0.272, p = 0.246; r = −0.245, p = 0.298; r = 0.313, p = 0.178, respectively) among depressive exercise training individuals (Figure 3).