Additionally, there is an association between depression and the SNP rs6296 of HTR1B [23,61,62], HTR2A rs6561333 with cocaine dependence [63], HTR3B rs11606194 over time to relapse after smoking cessation and with nicotine dependence [60,63,64], and HTR3B rs1176744 with alcohol and nicotine dependence [58–60]. Here, HTR1B is linked to major depressive disorder.