5-HT is involved in the occurrence of PTSD by interacting with the 5-HT transporter, 5-HT receptor (including 5-HT1A, 5-HT1B, 5-HT2A, and 5-HT2C receptors), and the neurotransmitters dopamine and norepinephrine. This evidence concerns the gene HTR1A and post-traumatic stress disorder.