In the recent past, the involvement of glutamate (excitatory neurotransmitter) pathway [157, 163, 246, 283] and the cross talk of glutaminergic (NMDA) and serotonergic (5-HT1A/2A) systems (mainly in the prefrontal cortex) has been implicated in molecular basis of depression [334]. Here, HTR1A is linked to depressive disorder.