Serotonin receptors, particularly 5-HT1A and 5-HT2A, play an important role [24], along with dopamine D2 and D3 receptors, which are implicated in the reward system and motivation—these neurotransmitter systems are often disrupted in depression [90] and may also play a role in suicidality [91]. This evidence concerns the gene HTR1A and depressive disorder.